LIGNOPHYTA

Plant a shrub or tree; true roots +, origin endogeneous, root cap +, apex multicellular; endodermis +; shoot apical meristem multicellular; lateral meristems +, cork cambium producing cork abaxially, vascular cambium producing phloem abaxially and xylem adaxially; lamina with mean venation density 1.8 mm/mm² (to 5 mm/mm²).

EXTANT SEED PLANTS/SPERMATOPHYTA

Plant woody, evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins derived from (some) sinapyl and particularly coniferyl alcohols, thus containing p-hydroxyphenyl and guaiacyl lignin units, so no Maüle reaction; root xylem exarch, cork cambium deep seated; arbuscular mycorrhizae +; shoot apical meristem interface specific plasmodesmatal network; stem with vascular tissue around central pith [eustele], vascular bundles with interfascicular tissue, ectophloic, endodermis 0, xylem endarch; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, sieve tube plastids with starch grains; phloem fibres +; stem cork cambium superficial; branches exogenous; leaves with single trace from vascular sympodium ["nodes 1:1"]; vascular bundles collateral [stem: phloem external; leaf: phloem abaxial]; stomata morphology?, pore opening controlled by abscisic acid; leaves with petiole and lamina, spiral, development basipetal, blade simple; axillary buds +, not associated with all leaves; prophylls two, lateral; plant heterosporous, sporangia borne on sporophylls; microsporophylls aggregated in indeterminate cones/strobili; true pollen +, grains mono[ana]sulcate, exine and intine homogeneous; ovules unitegmic, parietal tissue 2+ cells across, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development first endo- then exosporic, tube developing from distal end of grain, to ca 2 mm from receptive surface to egg, gametes two, developing after pollination, with cell walls, flagellae numerous; ovules increasing considerably in size between pollination and fertilization, female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large" [ca 8 mm³], but not much bigger than ovule, with morphological dormancy; embryo cellular ab initio, endoscopic, plane of first cleavage of zygote transverse, suspensor +, short-minute, embryo straight, shoot and root at opposite ends [allorrhizic], white, cotyledons 2; plastid transmission maternal; ycf2 gene in inverted repeat, two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], nrDNA with 5.8S and 5S rDNA in separate clusters; mitochondrial nad1 intron 2 and coxIIi3 intron and trans-spliced introns present.

MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], S [syringyl] lignin units common, positive Maüle reaction [syringyl:guaiacyl ratio more than 2-2.5:1], and hemicelluloses as xyloglucans; root apical meristem intermediate-open; root vascular tissue oligarch [di- to pentarch], lateral roots arise opposite or immediately to the side of [when diarch] xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0, exodermis +; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, associated gelatinous fibres [g-fibres] with innermost layer of secondary cell wall rich in cellulose and poor in lignin; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, wood parenchyma +; sieve tubes enucleate, sieve plate with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, cytoplasm not occluding pores of sieve plate, companion cell and sieve tube from same mother cell; sugar transport in phloem passive; nodes unilacunar [1:?]; stomata brachyparacytic [ends of subsidiary cells level with ends of pore], outer stomatal ledges producing vestibule; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, secondary veins pinnate, overall growth ± diffuse, venation hierarchical, fine venation reticulate, veins (1.7-)4.1(-5.7) mm/mm², endings free; most/all leaves with axillary buds; flowers perfect, pedicellate, ± haplomorphic, parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P not sharply differentiated, with a single trace, outer members not enclosing the rest of the bud, often smaller than inner members; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], ± embedded in the filament, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally, endothecium +, endothecial cells elongated at right angles to long axis of anther; tapetum glandular, cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellar, endexine thin, compact, lamellate only in the apertural regions; nectary 0; G superior, free, several, ascidiate, with postgenital occlusion by secretion, stylulus short, hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, dry [not secretory]; ovules few [?1]/carpel, marginal, anatropous, bitegmic, micropyle endostomal, outer integument 2-3 cells across, often largely subdermal in origin, inner integument 2-3 cells across, often dermal in origin, parietal tissue 1-3 cells across [crassinucellate], nucellar cap?; megasporocyte single, hypodermal, megaspore tetrad linear, functional megaspore chalazal, lacking sporopollenin and cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; ovule not increasing in size between pollination and fertilization; pollen binucleate at dispersal, male gametophyte trinucleate, germinating in less than 3 hours, pollination siphonogamous, tube elongated, growing between cells, growth rate 20-20,000 µm/hour, outer wall pectic, inner wall callose, with callose plugs, penetration of ovules via micropyle [porogamous], whole process takes ca 18 hours, distance to first ovule 1.1-2.1 mm; male gametes lacking cell walls, flagellae 0, double fertilization +, ovules aborting unless fertilized; P deciduous in fruit; seed exotestal, becoming much larger than ovule at time of fertilization; endosperm diploid, cellular [micropylar and chalazal domains develop differently, first division oblique, micropylar end initially with a single large cell, divisions uniseriate, chalazal cell smaller, divisions in several planes], copious, oily and/or proteinaceous; embryogenesis cellular; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, ndhB gene 21 codons enlarged at the 5' end, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, paleo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]].

[NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]]: vessels +, elements with elongated scalariform perforation plates; wood fibres +; axial parenchyma diffuse or diffuse-in-aggregates; pollen monosulcate [anasulcate], tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

[AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood 0; tectum reticulate; anther wall with outer secondary parietal cell layer dividing; carpels plicate; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.

[[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]] / MESANGIOSPERMAE: benzylisoquinoline alkaloids +; polyacetate derived anthraquinones + [?level]; outer epidermal walls of root elongation zone with cellulose fibrils oriented transverse to root axis; P more or less whorled, 3-merous [possible positiion]; embryo sac bipolar, 8 nucleate, antipodal cells persisting; endosperm triploid; ?germination.

[MONOCOTS [CERATOPHYLLALES + EUDICOTS]]: (veins in lamina often 7-17mm/mm² or more [mean for eudicots 8.0]); (stamens opposite [two whorls of] P); (pollen tube growth fast).

MONOCOTYLEDONS / MONOCOTYLEDONEAE / LILIANAE Takhtajan

Plant herbaceous, perennial, rhizomatous, growth sympodial; non-hydrolyzable tannins [(ent-)epicatechin-4] +, neolignans, benzylisoquinoline alkaloids 0, hemicelluloses as xylans; root apical meristem?; root epidermis developed from outer layer of cortex; trichoblast in atrichoblast [larger cell]/trichoblast cell pair further from apical meristem, in vertical files, or hypodermal cells dimorphic; endodermal cells with U-shaped thickenings; cork cambium in root [uncommon] superficial; root vascular tissue oligo- to polyarch, medullated, lateral roots arise opposite phloem poles; primary thickening meristem +; vascular bundles in stem scattered, (amphivasal), closed, vascular cambium 0; vessel elements in root with scalariform and/or simple perforations; tracheids only in stems and leaves; sieve tube plastids with cuneate protein crystals alone; stomata parallel to the long axis of the leaf, in lines, brachyparacytic; leaves with broad sheath plus blade [not petiole plus lamina], blade linear, main venation parallel, veins joining successively from the outside at the apex, endings not free, margins entire, (teeth spiny), Vorläuferspitze +, leaf base sheathing, sheath open, colleters [intravaginal squamules] +; prophyll single, adaxial; inflorescence terminal, racemose; flowers 3-merous [6-merous to the pollinator?], polysymmetric, pentacyclic; P = T, each member with three traces, median member of outer whorl abaxial, aestivation open, members of whorls alternating, similar, [pseudomonocyclic, each providing a sector for the T tube when present]; stamens = and opposite each T member [primordia often associated, and/or A vascularized from tepal trace], anther and filament more or less sharply distinguished, anthers subbasifixed, endothecium from outer secondary parietal cell layer, inner secondary parietal cell layer dividing; G [3], with congenital intercarpellary fusion, opposite outer tepals [thus median member abaxial], placentation axile; ovule with outer integument often largely dermal in origin, parietal tissue 1 cell across; antipodal cells persistent, proliferating; fruit a loculicidal capsule; seed testal; endosperm with distinct nuclear and chalazal chambers, embryo long, cylindrical, cotyledon 1, apparently terminal, plumule apparently lateral; primary root unbranched, not very well developed, "adventitious" roots numerous, hypocotyl short, (collar rhizoids +), cotyledon with a closed sheath, unifacial [hyperphyllar], both assimilating and haustorial; duplication producing monocot LOFSEP and FUL3 genes, [latter duplication of AP1/FUL gene], PHYE gene lost.

[ALISMATALES [PETROSAVIALES [[DIOSCOREALES + PANDANALES] [LILIALES [ASPARAGALES + COMMELINIDS]]]]]: ethereal oils 0; raphides + (druses 0); leaf blade vernation variants of supervolute-curved; endothecium develops directly from undivided outer secondary parietal cells; tectum reticulate with finer sculpture at the ends of the grain, endexine 0; (septal nectaries + [intercarpellary fusion postgenital]).

[PETROSAVIALES [[DIOSCOREALES + PANDANALES] [LILIALES [ASPARAGALES + COMMELINIDS]]]]: cyanogenic glycosides uncommon; starch grains simple, amylophobic; leaf blade developing basipetally from hyperphyll/hypophyll junction; epidermis with bulliform cellls [?level]; stomata anomocytic, (cuticular waxes as parallel platelets); colleters 0.

[[DIOSCOREALES + PANDANALES] [LILIALES [ASPARAGALES + COMMELINIDS]]]: nucellar cap 0; endosperm nuclear [but variation in most orders].

[LILIALES [ASPARAGALES + COMMELINIDS]]: (inflorescence branches cymose).

[ASPARAGALES + COMMELINIDS]: style long.

COMMELINIDS

Unlignified cell walls with UV-fluorescent ferulic and coumaric acids; (vessels in stem and leaves); SiO₂ bodies +, in leaf bundle sheaths; stomata para- or tetracytic, (cuticular waxes as aggregated rodlets [looking like a scallop of butter]); inflorescence branches determinate, peduncle bracteate; T = calyx + corolla [stamens adnate to corolla/inner whorl]; pollen starchy; embryo short, broad.

Phylogeny. Relationships of the main groups within commelinids are unclear; for further information, see discussion preceding Dasypogonaceae, also Commelinales and Zingiberales.

[POALES [COMMELINALES + ZINGIBERALES]]: primary cell wall mostly with glucurono-arabinoxylans; stomata subsidiary cells with parallel cell divisions; endosperm reserves starchy.

Evolution. Divergence & Distribution. The stem group for this clade dates to about 120 m.y.a., while Poales diverged from [Commelinales + Zingiberales] ca 117 m.y.a. (Janssen & Bremer 2004); Magallón and Castillo (2009, which consult for more details) suggest ca 123 m.y. or 111 m.y. for crown group diversification, the stem group age being 128 to 115 m.y. (relaxed and constrained estimates respectively).

Plant-Animal Interactions. Sap-eating chinch bugs of the Hemiptera-Lygaeidae-Blissinae have been recorded from taxa throughout this clade, although they occur on Poales and especially Poaceae most frequently (Slater 1976).

Chemistry, Morphology, etc. For primary cell wall composition, see literature in Harris (2005); Arecaceae sampled are somewhat intermediate between this clade and other monocots. For stomatal development, see Tomlinson (1974) and Rudall (2000); development in Dasypogonaceae is apparently unknown.

Previous Relationships. Engler (1892) recognised a group, Farinosae, distinguished by its starchy endosperm, which included many of the taxa now in this clade. Engler thought that Farinosae were close to his Liliflorae, perhaps partly because he included Juncaceae in the latter.

POALES Small  Main Tree, Synapomorphies.

Mycorrhizae absent; vessel elements in roots often with simple perforation plates, vessels also in stem and leaf, also with simple perforation plates; SiO₂ epidermal; raphides 0; inflorescence indeterminate; style well developed, stigmas small, dry; micropyle bistomal, both integuments ca 2 cells across; endosperm nuclear, embryo size?; cotyledon hyperphyllar, haustorial [?level]; mitochondrial sdh3 gene lost. - 17 families, 997 genera, 18325 species.

Note: Possible apomorphies are now being added throughout the site; they are in bold. However, the actual level at which many of these features, particularly the more cryptic ones, should be assigned is unclear. This is because there is very considerable homoplasy, with variation within and between clades, for most characters. Furthermore, the basic information for all too many characters is very incomplete, often coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there is the not-so-trivial issue of how ancestral states are reconstructed...

Evolution. Divergence & Distribution. Crown-group diversification may begin ca 113 m.y.a. (Janssen & Bremer 2004) or 109-106 m.y.a. (Leebens-Mack et al. 2005). However, Wikström et al. (2001) suggest a much younger age for the stem clade of 87-83 m.y., divergence beginning 72-69 m.y.. Magallón and Castillo (2009, which consult for more details) suggested ca 109 m.y. for relaxed and 99.2 m.y. for constrained penalized likelihood crown group datings - probably underestimates.

However, there are problems. Poinar (2004, 2011) proposed that Programinis laminatus, found fossil in deposits from the Early Cretaceous of Myanmar some 110-100 m.y.a., represented Poaceae-Pooideae, i.e. a clade rather highly embedded in Poaceae. Similarly, if the identity of the putative stem Bromeliaceae Protoananas lucenae, 114-112 m.y. old and from Brazil, is confirmed (Leme & Brown 2011) - old dates for the clade are again suggested.

Linder and Rudall (2005) give a detailed discussion of morphological evolution and diversification in Poales. Magallón and Castillo (2009) suggest that Poales in the broad sense have the highest diversification rate in the monocots, about the same as Asparagales, but in both the rate is little over half that of Lamiales.

Ecology & Physiology. Cornwell et al. (2008) found that litter decomposition of forbs was faster than that of graminoids - presumably mostly grasses and sedges - indeed, litter decomposition of monocots (sic) was slower that that of other angiosperms; such differences are connected with the rate of nutrient cycling in the environment.

Plant-Animal Interactions. Many host-plants of reed beetles, Chrysomelidae-Donaciinae, are scattered in Poales, especially in Typhaceae, Juncaceae, and Cyperaceae (Kölsch & Pedersen 2008: much discussion on the age and evolution of the group). They show close co-speciation with endosymbiotic bacteria (gamma proteobacteria-Enterobacteriaceae - near Buchnera), which are believed to produce the material that makes up the cocoon that characterises this beetle clade, which is also noted for the larvae being able to grow under water (Kölsch & Pedersen 2010).

Pollination Biology & Seed Dispersal. For the repeated evolution of wind pollination in Poales, see Givnish et al. (2010a, b).

Chemistry, Morphology, etc. Eriocaulaceae, Poaceae, Cyperaceae and Juncaceae at least have lateral roots originating opposite the phloem of the vascular tissue, in Restionaceae and Bromeliaceae they originate opposite the xylem (ref.?). Note that at least some of the Poaceae and Cyperaceae groups have distinctive cellulose orientation in the outer epidermal walls of their roots, but that some Typhaceae and Bromeliaceae do not (Kerstens & Verbelen 2002); one wonders what improved sampling will show.

There is variation in the way pollen is arranged in the pollen loculi. The plesiomorphous condition is likely to be central, i.e., some pollen grains are not in contact with the tapetum, but in some taxa it is peripheral, and here all grains are in contact with the tapetum (Kirpes et al. 1996), however, sampling is poor. See Doyle et al. (1991) for chloroplast inversions, Prychid et al. (2004) for SiO₂ bodies, Ong and Palmer (2006) for the rps14 nuclear gene/mitochondrial pseudogene system, and Tillich (2007) for seedling morphology and evolution.

Phylogeny. The order itself does not always have very strong support, but c.f. e.g. Givnish et al. (2010b), Barrett et al. (2012b), etc. The topology of the tree in early versions of this site was based on the work of K. Bremer (2002) in particular, and also that of Harborne et al. (2000), but Janssen and Bremer (2004) suggested a rather different set of relationships, albeit some had little support, and relationships in Givnish et al. (2010b) are somewhat different again. It will become clear from the discussion below that the topology of the tree above is probably incorrect in detail, but I await further studies with better sampling and support before changing it.

The general pattern of movement of genes from the mitochondrion to the nucleus suggests that Bromeliaceae and Typhaceae (of the taxa sampled) are sister to other Poales (Adams & Palmer 2003), and of course Bromeliaceae, along with Rapateaceae, alone have septal nectaries in this clade. Bromeliaceae and Typhaceae are often placed as basal branches with respect to other clades in Poales (Givnish et al. 2005, 2008 [but rooting]; also Graham et al. 2006), while Rapateaceae appear to be sister to remaining Poales in some analyses (e.g. Davis et al. 2004), albeit with little support. A three-nucleotide deletion in the atpA gene was found to characterise Typhaceae and Bromeliaceae (Davis et al. 2004), although there was little bootstrap support for this group (but see also Givnish et al. 2005, 2007; c.f. Givnish et al. 2006b). Similarly, Typhaceae are placed sister to Bromeliaceae with weak jacknife support but strong Bayesian posterior probabilities (Bremer 2002). Other work also suggests that Typhaceae and Bromeliaceae form a clade sister to other Poales, and Rapateaceae are in turn sister to the remainder (Chase et al. 2006; also Rudall & Linder 2005; Givnish et al. 2005, 2007: ?rooting; Graham et al. 2006: see Rapateaceae; Soltis et al. 2011: strong support, but sampling), although these relationships are not always obtained (Givnish et al. 2010a). Indeed, Givnish et al. (2010b) found quite strong support in both maximum parsimony and maximum likelihood plastome analyses for the topology [Bromeliaceae [Typhaceae s.l. [Rapateaceae + rest of Poales]]] (see also Barrett & Davis 2011; Barrett et al. 2013; Davis et al. 2013: again, both ML and MP trees).

Within remaining Poales there are some well-supported clades, the Xyridaceae, Juncaceae, and Poaceae groups, although the exact composition of the first clade remains somewhat unclear. There is support for these three groups forming a larger clade (e.g. Givnish et al. 2005, 2010b; Chase et al. 2006), perhaps compatible with the distribution of deletions in the chloroplast inverted repeat ORF 2280 region and absence of a full accD gene (Hahn et al. 1995; Katayama & Ogihara 1996).

Xyridales of Kubitzki (1998c) included Mayacaceae, Xyridaceae, Eriocaulaceae and Rapateaceae. However, there was some evidence for a group made up of the first three families, perhaps, but not very probably, also including Rapateaceae (Rapateaceae are sister to [Juncaceae + Xyridaceae + Poaceae groups] in Givnish et al. 2005). Bremer (2002) noted that Mayacaceae and Hydatellaceae might be weakly associated with Xyridaceae or Eriocaulaceae, depending on what taxa were included in the analysis, but there were a number of long branches in this area and he excluded the first two families from his final analysis (Chase et al. 2006 also found the position of Hydatellaceae to be problematic; for the association of Mayacaceae with Eriocaulaceae and Xyridaceae, see also Campbell et al. 2001). Davis et al. (2004) found a more complex set of relationships, although with very little support. Members of this group of families were in adjacent branches along the spine of the tree, with one including Flagellariaceae, the Juncaceae group, some Xyridaceae, Mayacaceae, and perhaps Hydatellaceae. Note also that Xyridaceae and Mayacaceae have more or less clawed petals and anthers with an exothecium. Finally, some studies (ref.?) have linked Mayacaceae with Rapateaceae, and both have poricidal anthers. Clearly, there are a number of distinctive characters in this group of families, but relationships within the group remain unclear.

The situation may, however, be becoming a little tidier. Saarela et al. (2006, esp. 2007) showed that Hydatellaceae are completely misplaced and belong to Nymphaeales, being sister to other members of that clade, and this new position has very strong molecular and morphological support. The three members of the old Xyridales that remain here may form a grade as follows: [Mayacaceae [[Xyridaceae + Eriocaulaceae] [Thurniaceae [Juncaceae + Cyperaceae]]]] (Givnish et al. 2006b; Chase et al. 2006); the topology of the tree in Graham et al. (2006) although with poor sampling, is consistent with such relationships. Givnish et al. (2010b) found that Abolboda, the only member of Xyridaceae examined, did not link with the Eriocaulaceae-Mayacaceae clade in maximum likelihood analyses, while in maximum parsimony analyses there was some support for the clade [Juncaceae etc. + Xyridaceae etc.] (the latter grouping was also recovered by Davis et al. 2013). In maximum likelihood analyses the general relationships were [[Juncaceae, etc.] [[Xyridaceae etc.] [Abolboda [Poaceae, etc.]]]] (Givnish et al. 2010b). Generally similar relationships were found by Barrett and Davis (2011), while Davis et al. (2013) found the grouping {Eriocaulaceae/Mayaceae [Xyridaceae + Restionaceae/Poaceae area]], but there Abolboda stayed with other Xyridaceae).

Poaceae and their immediate relatives consistently form a clade, although details of relationships within it are still somewhat unclear (see below). Note that in versions 6 [before November] and earlier of this site, Eriocaulaceae and their relatives were weakly associated with the Poaceae group, perhaps unlikely.

Includes Anarthriaceae, Bromeliaceae, Centrolepidaceae, Cyperaceae, Ecdeiocoleaceae, Eriocaulaceae, Flagellariaceae, Joinvilleaceae, Juncaceae, Mayacaceae, Poaceae, Rapateaceae, Restionaceae, Thurniaceae, Typhaceae, Xyridaceae.

Synonymy: Eriocaulineae Thorne & Reveal, Xyridineae Thorne & Reveal - Avenales Bromhead, Bromeliales Link, Centrolepidales Takhtajan, Cyperales Berchtold & J. Presl, Eriocaulales Nakai, Flagellariales Reveal & Doweld, Juncales Berchtold & J. Presl, Mayacales Nakai, Rapateales Reveal & Doweld, Restionales Berchtold & J. Presl, Typhales Berchtold & J. Presl, Xyridales Lindley

[Typhaceae + Bromeliaceae]: stomatal subsidiary cells with oblique divisions; leaf without distinct sheath; endosperm helobial, cell wall formation in small chalazal chamber before that in large micropylar chamber; three-nucleotide deletion in the atpA gene.

TYPHACEAE Jussieu, nom. cons.   Back to Poales

Flavonoids +; SiO₂ bodies 0; starch grains pteridophyte-type, amylophilic; leaves two-ranked; plant monoecious; inflorescences dense, complex, gap between staminate and pistillate inflorescences; flowers very small, monosymmetric by reduction; P chaffy; A 1-8; tapetum plasmodial, 8 nuclei/cell; pollen grains trinucleate, monoulcerate; nectary 0; G pseudomonomerous, style single, stigma rather elongated, on one side, dry; ovule 1/carpel, pendulous, apotropous, nucellar cap ca 2 cells across, obturator +; fruit indehiscent; seed coat ± obliterated; endosperm +, perisperm +, thin, embryo long, slender; x = 15; ORF 2280 deletion; seedling with hypocotyl and collar hairs.

2/ca 25. More or less world-wide.

Sparganium L.

Stomatal subsidiary cells with intersecting oblique divisions; inflorescence as globose heads; P 1-6, when 3, median member adaxial; staminate flowers: anthers extrorse-latrorse; pollen mixed with raphides; carpellate flowers: stigma papillate; antipodal cells multiply after fertilisation; fruit a spongy drupe, with micropylar plug, P persistent; testa membranous; perisperm with oil; phanomer [unifacial, ± assimilating], hypophyll quite well developed.

1/14. Temperate and Arctic, little in S. hemisphere, but to New Zealand (map: see Hultén 1958, 1962; Meusel et al 1965; Hultén & Fries 1986).

Synonymy: Sparganiaceae Hanin, nom. cons.

Typha L.

Stems lacking vessels; (styloids +); cuticular waxes as aggregated rodlets; leaf with distinct sheath; inflorescence densely spicate, (no gap between staminate and pistillate part); P 0; staminate flowers: A connate; (pollen in tetrads); carpellate flowers: long hairs on pedicels; G stipitate, fruit an achene with a little operculum; endosperm also with oil.

1/8-13. Temperate and tropical regions worldwide (map: see Hultén 1962; Meusel et al. 1965; Hultén & Fries 1986; Flora Base 2005 - somewhat notional: the map in Knobloch & Mai 1986 differs very considerably from its source, Meusel et al. 1965). [Photos - Collection]

• Sparganium is a rhizomatous aquatic with linear leaves and inflorescences with a few spherical heads of flowers, carpellate towards the base of the inflorescence and staminate towards the apex. Typha is a robust, rhizomatous herb that likes damp conditions and has erect, linear leaves and distinctive, elongated, densely cylindrical inflorescences, the part containing the carpellate flowers being borne below and separate from the part with the staminate flowers.

Evolution. Divergence & Distribution. Typhaceae are ca 109 m.y. old, the two genera separating ca 89 m.y.a. (Janssen & Bremer 2004).

For the rich fossil record of the family - although Cretaceous occurrences need re-evaluating - see Smith et al. (2010); fossil Sparganium may have up to 7-locular fruits (Cook & Nicholls 1986). Collinson and van Bergen (2004) found similar chemical signatures in fruits of extant and fossil representatives of both genera.

Bacterial/Fungal Associations. Similar rusts are shared by the two genera (Savile 1979).

Chemistry, Morphology, etc. Some flowers of Sparganium may have a second, empty loculus, or there may even be three fertile loculi (Dahlgren et al. 1985). Given the records of multilocular fruits in the genus (see above), it seems likely that the pseudomonomerous gynoecium in the two genera evolved independently.

Much information is taken from Kubitzki (1998d: general); see also D. Müller-Doblies (1970: inflorescence and flower) and Grayum (1992) and Albert et al. (2011), both pollen - the two genera are palynologically almost identical. For general information on Typha, see Thieret and Luken (1996: southeast U.S.A.). See U. Müller-Doblies (1970) for flower and embryology and Carlquist (2012a) for vessels in Sparganium.

Phylogeny. For phylogenetic relationships in Typha, see Kim and Choi (2011).

Classification. See Cook and Nicholls (1986, 1987) for a monograph of Sparganium.

BROMELIACEAE Jussieu, nom. cons.   Back to Poales

Rosette plants; (C-glycosylated/6-oxygenated) flavones, flavonols +; vessel elements with scalariform perforation plates; mucilage +; cuticular waxes as aggregated rodlets; water storage tissue in mesophyll, fibrous bundle sheaths + [?higher level]; indumentum lepidote; leaves spiral, blade vernation curved, thick, horny, base dilated; (A basally connate), (adnate to C); septal nectaries +, style +, long, apically ± 3-branched, branches conduplicate-spiral, stigmas also wet; ovules 2-many/carpel, nucellar epidermis cells anticlinally elongated [?all], (nucellar cap ca 2 cells across); fruit a septicidal capsule, K persistent; seeds testal-tegmic, testa 3-7 cells across, cells variously thickened and lignified, tegmen ca 2 cells across, (exotegmen thickened), endotegmen tanniniferous; embryo (long), cylindrical, often lateral; hypocotyl and hypophyll common; x = 25, chromosomes 2.75³ µm long.

57[list]/1770 - eight groups below. (Sub)tropical America; W. tropical Africa (map: from Givnish 2004a). [Photo - Flower.]

(Tank epiphytes), (stem erect and with intracauline adventitious roots), (plant carnivorous); leaves with stellate chlorenchyma, margin ?; C minute; G ± inferior, septal nectary above the insertion of the ovules; seeds caudate, (basal tuft of hairs +); n = ?9, 23.

1/21. South America, the Guyana Highlands (map: from Smith & Downs 1974).

[Lindmanioideae [Tillandsioideae [Hechtioideae [Navioideae [Pitcairnioideae [Puyoideae + Bromelioideae]]]]]]: cap cells of trichomes dead; septal nectaries below the insertion of the ovules.

2. Lindmanioideae Givnish

Stellate chlorenchyma 0; leaf margin entire/serrate; K contorted; stigmas straight; seeds caudate; cotyledonary hypophyll blade-like.

1-2/43. South America, the Guyana Highlands.

[Tillandsioideae [Hechtioideae [Navioideae [Pitcairnioideae [Puyoideae + Bromelioideae]]]]]: (inflorescence axis, bracts, floral bracts coloured); (C often with subbasal scales and/or longitudinal callosities).

3. Tillandsioideae Burnett

Air epiphytes, (also tank-forming), roots often for attachment only (0); scales radially symmetric; leaf margins entire; (flowers in inflorescence two-ranked); (pollen with raphides); ovules with long chalazal projection, (outer integument ca 5 cells across); seeds caudate because of greatly elongating outer integument, apical and/or basal tufts of hair usu. derived from longitudinal splitting of the outer integument; embryo short to long; (n = 17, 21), karyotype bimodal; (primary root none or soon aborting).

9/1015: Tillandsia (620: polyphyletic), Vriesia (195: poly/paraphyletic), Guzmania (170), Werauhia (70), Racinaea (60). Almost the range of the family in America.[Photo - Flower]

Synonymy: Tillandsiaceae Wilbread

[Hechtioideae [Navioideae [Pitcairnioideae [Puyoideae + Bromelioideae]]]]: ?

4. Hechtioideae Givnish

Plant xeromorphic; (CAM photosynthesis +); hypodermal sclerenchyma +, internal water storage tissue +, chlorenchyma undifferentiated; trichomes in parallel rows; leaf margin serrate (entire); plants dioecious; (G subinferior), stigma simple-erect; seeds circumferentially winged (not); cotyledonary hypophyll blade-like.

1/51. Texas, Mexico, N. Central America.

[Navioideae [Pitcairnioideae [Puyoideae + Bromelioideae]]]: ?

5. Navioideae Harms

Plant xeromorphic; peripheral water storage tissue +, stellate chlorenchyma 0; leaf margin serrate/entire; C minute; seeds circumferentially winged or not.

5/105: Navia (98). Guyana Highlands, N.E. Brasil.

[Pitcairnioideae [Puyoideae + Bromelioideae]]: ?

6. Pitcairnioideae Harms

Scales ± divided, or hairs stellate; leaf margin?; (flowers monosymmetric), G to inferior; ovules with chalazal appendage, (outer integument ca 5 cells across), (parietal tissue several cell layers across); seeds tailed, body cells differing from tails, winged, or not; embryo lateral or not; (karyotype bimodal); hypocotyl quite long, cotyledonary hypophyll blade-like, (collar rhizoids - Pitcairnia).

5/515: Pitcairnia (405), Dyckia (150), Forsterella (30). Mexico to Chile, Pitcairnia feliciana W. Africa.

[Puyoideae + Bromelioideae]: ?

7. Puyoideae Givnish

Plant rather xeromorphic; hypodermal sclerenchyma +, internal water storage tissue +, chlorenchyma undifferentiated; trichomes in parallel rows, foliar trichomes ± well developed scales; leaf margin serrate; flowers monosymmetric, K contorted, C clawed, tightly spiralled after anthesis; parietal tissue several cell layers across [?all]; seeds circumferentially winged; cotyledonary hypophyll blade-like.

1/195. Mountains, etc., Costa Rica and Guyana to Chile and Argentina. [Photos - Puya Flower, Puya Habit, Puya Habit.]

8. Bromelioideae Burnett

Epiphytes, often tank-forming, roots often for attachment only; CAM photosynthesis common; scales irregularly peltate; leaf margin entire/serrate; (perianth tube/hypanthium +), (K asymmetric), (C with adaxial subbasal petal appendages); (pollen porate), (with raphides); G inferior, ovules with chalazal [= funicular] appendage, micropyle also endostomal, stigma conduplicate, spiral; fruit baccate; seed usu. without an appendage; sarcotesta [gelatinous] common; embryo lateral; (n = 17, 21); (cotyledon not photosynthetic), collar rhizoids +, primary root prominent, short hypocotyl present; (n = 17).

31/722: Aechmea (185), Neoregelia (100), Billbergia (65), Bromelia (50), Hohenbergia (50), Nidularium (50). Mexico and the West Indies to Chile, esp. Brazil. [Photo - Flower, Fruit, Flower, Flower.]

• Bromeliaceae are often rosette plants, the leaves always being tough, spirally arranged, lacking a distinct sheath, and often with spiny-toothed margins; the indumentum is scaly (lepidote); and the terminal inflorescence is prominently bracteate, the bracts sometimes being coloured. The flowers have a calyx and corolla, and the petals, although free, are erect and form a tube.

Evolution. Divergence & Distribution. Stem-group Bromeliaceae are dated to ca 112 m.y., the crown group to ca 96 m.y. (Janssen & Bremer 2004: Brocchinia not included). Other estimates are much more recent. Wikström et al. (2001) suggest a stem group age of 72-69 m.y., and Givnish et al. (2004a, 2008a) stem ages of ca 84 and crown ages of a mere 23-19 m.y. respectively, with radiation from an ancestral home on the Guayana Shield (see also Givnish et al. 1997, 2011a: much detail, b). Indeed, Givnish et al. (2011a, b) proposed that there was a ca 80 million year hiatus between the origin of stem and crown Bromeliaceae (stem ca 100 m.y., crown ca 19 m.y.); perhaps there was much extinction.

The situation is becoming yet more confused. Protoananas lucenae, from the Crato limestone of Brazil and some 114-112 m.y. old, has been assigned to a "putative ancestral stem-lineage of Bromeliaceae" (Leme & Brown 2011: p. 217), but in the discussion it is also referred to as if it were in a separate family, Protoananaceae. It appears to have an inferior ovary, presumably of independent origin from that found in other Bromeliaceae (but see below: superior ovaries in some Bromeliaceae are thought by some to be secondarily so).

Givnish et al. (2004a, 2008a) provide a phylogeny and discuss the biogeography of the group, while Givnish et al. (2008) also discuss the evolution of CAM, bird pollination, epiphytism and xeromorphic traits (see also Smith et al. 2005; Nyffeler & Eggli 2010b). For diversification rates in the family, particularly high in tank epiphytes, see Givnish et al. (2011b).

Plant-Animal Interactions. Nymphalinae-Riodininae larvae may be found on Bromeliaceae (and Orchidaceae: Hall 2003 and references). Some epiphytic Bromeliaceae are more or less closely associated with ants (Benzing 1990); see below for the inhabitants of tanks and their importance.

Pollination Biology & Seed Dispersal. Bird pollination is common in Bromeliaceae (Stiles 1981 and references; Givnish et al. 2008), although entomophily is probably the ancestral condition (Givnish et al. 2011b). It is odd that there appears to be no prezygotic reproductive isolation between species of Bromeliaceae growing together in southeastern Brazil; the flowers are not notably different morphologically and flowering times overlap extensively, yet hybrids are very uncommon (Wendt et al. 2008) as they are in the family as a whole.

Dispersal is primarily by ingestion of fruits by animals or of the seeds by wind. Recent work suggests that the coma on the seeds of Catopsis (Tillandsioideae) may also assist materially in both germination and seedling establishment by taking up water which can be used by the plantlet; this could be critical in allowing the establishment of the plant in the epiphytic habitat where Catopsis grows and where water may be at a premium (Wester & Zotz 2011). Note that seed hairs in Tillandsioideae develop in a variety of ways, including the almost complete separation of series of exotestal cells from the rest of the seed (Rohweder 1956; Palací et al. 2004; Barfuss et al. 2005; Magalhães & Mariath 2012).

Ecology & Physiology. The diversity of growth form in Bromeliaceae is well known. Many taxa are terrestrial, and have a well-developed root system. However, about 1,700 species - and so just over half the family - are epiphytic, and are especially common in montane habitats (Benzing 1990 for much discussion; Luther & Norton 2008: epilithic species not included). Tillandsioideae predominate here, and some are air epiphytes, any roots being for attachment only (see below). A major clade in Bromelioideae, some Brocchinia, a few Tillandsioideae, etc., are tank epiphytes, the tanks being formed by the closely appressed overlapping bases of the leaves.

The multicellular hairs on the leaf surface are integral to the functioning of the different growth forms. Perhaps somewhat paradoxically, adaxial leaf surfaces in Bromelioideae and some other subfamilies are hydrophilic while abaxial surfaces are hydrophobic (Reuter & Brown 2009). Dense scales or a powdery epicuticular wax make the abaxial leaf surface wet and water-repellent so the stomata there remain functional even in wet conditions, and it has even been suggested that repelling water was an ancestral function of bromeliaceous scales (Pierce et al. 2001). The less dense scales on the adaxial surfaces of the leaves are involved in nutrient uptake (Benzing et al. 1985; Pierce et al. 2001) for which water is essential. Phosphate is taken up very efficiently by the hairs on the adaxial surfaces of the leaves in tank epiphytes like Aechmea fasciculata and either moved elsewhere in the plant or stored as phosphorous-containing phytin (Winkler & Zotz 2009; Gonsiska & Givnish 2009). Leaves of Bromeliaceae also do not seem to lose metabolites easily (Benzing & Burt 1970; McWilliams 1974).

The rather elegant multicellular peltate trichomes of Tillandsioideae, subjects of detailed early studies by Mez (1904), take in water and nutrients; they flex as they dry and so pull away from the leaf surface, but when it rains they readily take up water and then lie flat on the surface (Benzing 1976; Pierce et al. 2001); water and nutrient absorbtion takes place then. Dried scales in Tillandsia may also reflect light and so provide photoprotection (Pierce 2008). Roots in epiphytic Tillandsioideae may be for attachment only, and adult plants of Tillandsia usneoides (Spanish moss) lack roots entirely, the plants growing readily on any available support - branches, telegraph wires, etc. (Wester & Zotz 2010 and references); the leaves take over the nutritional function of roots. The rootless T. latfolia and T. pupurea are quite happy lying in the full sun in Peruvian deserts (McWilliams 1974). In at least some species that do develop roots, the radicle of the embryo aborts (Fiordi Cecchi et al. 1996; Magalhães & Mariath 2012).

In tank bromeliads the apical meristem is submerged and at the bottom of the tank, and in some species the flower buds develop under water and open above; the perianth then rots, but the ripe fruits are raised above the surface of the water by the elongation of their pedicels. Roots may grow into the tank where they absorb the contents; Pittendrigh (1948) noted that such roots were mycorrhizal, while roots growing into the soil were not obviously mycorrhizal. A diverse fauna showing considerable endemism is associated with the tanks; the animals include frogs, insects, land crabs, earthworms, ostracod crustaceans, protists and the like (Thienemann 1934; Benzing 1990; Kitching 2000; Greeney 2001: bibliography). Indeed, the evolution of a group of specialised diving beetles (Dystiscidae) may be almost contemporaneous with the appearance of the tank habitat (Balke et al. 2008), and tanks are also the habitat of a few carnivorous Utricularia. In Trinidad, at least, mosquitoes that breed in bromeliad tanks help spread malaria (Pittendrigh 1948).

Some two thirds of Bromelioideae have some form of CAM metabolism and ca 44% have strong CAM, although details of the evolution of this feature remain unclear (Crayn et al. 2000, 2004; Reinert et al. 2003; Schulte et al. 2005). CAM has evolved more than once here, with considerable plasticity evident even within genera like Puya (Schulte et al. 2011). Quezada and Gianoli (2011) consider the acquisition of CAM photosynthesis to consist of a series of key innovations; in five sister group comparisons the CAM clade was significantly more diverse than the non-CAM clade. CAM evolution may have occurred initially in the context of moving in to dry/arid terrestrial habitats, rather than as an adaptation facilitating epiphytism (Quezada & Gianoli 2011).

Carnivory may have evolved more than once in Bromeliaceae. The tillandsioid Catopsis berteroniana traps terrestrial arthropods, so it is possibly carnivorous; it harbours larvae of the mosquito Wyeomyia, which also inhabits the pitchers of Sarracenia (Frank & O'Meara 1984; Gonsiska & Givnish 2009). For possible carnivory in Brocchinia reducta, see Givnish et al. (1984) and Plachno and Jankun (2005). Brocchinia reducta does not produce nectar, only a sweet scent, but lives in the same area as the rather similar-looking and nectar-producing Heliamphora (Sarraceniaceae), and it has been suggested that the former is a Müllerian mimic of the latter (Joel 1988).

Brocchinia is only a small genus and is restricted to the Roraima region, but it has different growth forms and takes up nirogen in different ways. Givnish et al. (1997) discuss the diversification of the genus, which seems to have begun only ca 14 m.y.a. (Givnish et al. 2004a, 2008a). Some species are tank plants, and of these B. reducta may acquire nitrogen through carnivory (see above). Brocchinia acuminata is an ant plant.

Genes & Genomes. The rate of molecular evolution in Bromeliaceae is very low, ca 0.00059 substitutions/site/m.y.; although the family is not particularly woody, its members have a long generation time, which seems to be connected with this low rate of molecular evolution (Smith & Donoghue 2008).

Chemistry, Morphology, etc. The flowers of Tillandsia are shown as being inverted, but those of Bilbergia have the normal position with an abaxial median sepal (Spichiger et al. 2004); the former position is incorrect (W. Till, pers. comm.). Tapetum development is described as being intermediate, the cells initially being secretory, but tending to become invasive later (Sajo et al. 2005); the pollen of Tillandia leiboldiana is described as having a proximal sulcus (Albert et al. 2010). The superior ovary of Bromeliaceae such as Tillandsioideae may be secondarily so (Böhme 1988; Sajo et al. 2004b), although I find it difficult to understand why the vascular traces to the various floral organs should then often depart independently in these taxa; they are fused when the ovary is clearly inferior. Variation in stigma morphology in Tillandsioideae is great (Brown & Gilmartin 1989), and that in ovule morphology is extreme (e.g. Gross 1988a).

For additional information on petal appendages, see Brown and Terry (1992), on stigma morphology, see Brown and Gilmartin (1989), on the ovule, Sajo et al. (2004a), on fruit anatomy, see Fagundes and Mariath (2010), on seed anatomy, Szidat (1922), Rohweder (1956), Gross (1988a) and Varadarajan and Gilmartin (1988a), on germination, Gross (1988b), on chromosomal evolution, see Gitaí et al. (2005), on phytoliths, see Piperno (2006), on cultivated bromeliads, Rauh (1990), etc., on rhizome and root anatomy, see Proença and Sajo (2008), on tetraporate pollen of Hohenbergia, see Albert et al. (2011), and for general information, Varadarajan and Gilmartin (1988b), Smith and Till (1998) and Benzing (2000).

Phylogeny. For phylogeny, etc., I largely follow Givnish et al. (2008a: 1 gene, good generic sampling, few species, but note rooting of Fig. 1, also 2009, 2011a, b), which is rather similar to that in Schulte et al. (2005: focus on Bromelioideae). In earlier studies, Bromelioideae were monophyletic, even when Pitcairnioideae were included (Crayn et al. 2004: matK + rps16), however, in some studies (Horres et al. 2000) Puya did not link with them (see also Jabaily & Sytsma 2010). Hechtia and Navia were of uncertain position in Horres et al. (2000: trnL), but were weakly linked with Tillandsioideae in Crayn et al (2004); in that study Navia was polyphyletic. Support for Pitcairnioideae is weak (55% - Terry et al. 1997: ndhF), and the subfamily was not apparent in Horres et al. (2000), although there was a group of Pitcairnioideae genera, albeit with <50% bootstrap. See also Crayn et al. (2004) for phylogenetic problems with Pitcairnioideae; it has of course turned out to be eminently paraphyletic (see e.g. Givnish et al. 2007, 2011a). Givnish et al. (2011a) found strong support for most elements of the topology used here, support for the monophyly of Pitcairnioideae s. str. and for the position of Navioideae improving over earlier studies, but the monophyly of Puyoideae was still not well supported; Puya may be paraphyletic.

For the association of Ayensua with Brocchinia and the phylogeny of Brocchinioideae, see Givnish et al. (1997) and Horres et al. (2000). Weising et al. (2011) outline phylogenetic relationships within Pitcairnioideae. For relationships within Bromelioideae, see Horres et al. (2008), Schulte and Zizka (2008) and especially Schulte et al. (2009); Bromelia serra alone may be sister to the rest of the subfamily, although support for this position is weak, and there is a large clade including it and other taxa that are all tank epiphytes. For relationships within Forsterella, Bromelioideae s. str., see Rex et al. (2009 and references). Bromelioideae with tanks also often have flowers with asymmetric sepals and porate pollen (Schulte & Zizka 2008; Schulte et al. 2009).

For phylogenetic relationships in Tillandsioideae, see Barfuss et al. (2004, 2005: extensive discussion on morphology). Relationships within the Tillandsia group appear to need substantial realignments (Barfuss et al. 2011); Alcantarea is close to or embedded within Vriesia (Versieux et al. 2012). There is little phylogenetic structure along the backbone of Puya (Jabaily & Sytsma 2010: morphological study of Puya subgenus Puya; Hornung-Leoni & Sosa 2008: somewhat different relationships; Schulte et al. 2011). For other phylogenetic studies, see Crayn et al. (2000), and Givnish et al. (2004b: ndhF).

Classification. The family was monographed quite recently by Smith and Downs (1974, 1977, 1979), even if the supraspecific groups that they recognized have become dated. The subfamilial classification of Givnish et al. (2008a) is followed here; see also the World Checklist of Monocots. Barfuss et al. (2005) provide a tribal classification of Tillansioideae. Generic limits need attention in much of the family. Thus within Bromelioideae, Aechmea is hopelessly poly/paraphyletic (Schulte et al. 2009; Sass & Specht 2010) and generic limits there are generally unclear (Horres et al. 2008).

[Rapateaceae [[[Eriocaulaceae + Xyridaceae] [Mayacaceae [Thurniaceae [Juncaceae + Cyperaceae]]]] [[Anarthriaceae [Restionaceae + Centrolepidaceae]] [Flagellariaceae [[Joinvilleaceae + Ecdeiocoleaceae] Poaceae]]]]]: little oxalate accumulation; embryo minute, ± undifferentiated.

Chemistry, Morphology, etc. For oxalate accumulation, see Zindler-Frank (1976); I do not know about accumulation in Xyridaceae and Eriocaulaceae (the latter has calcium oxalate crystals, at least) and the small families in the Poacaeae-Restionaceae clade. The exact condition of the embryo of the ancestor of this group is unclear. Malcomber et al. (2006) described the embryo of Joinvilleaceae and Ecdeicoleaceae as being undifferentiated, embryos of Centrolepidaceae seem to be undifferentiated (Hamann 1975), those of Restionaceae, largely undifferentiated (Linder et al. 1998), of Mayacaceae, undifferentiated (Stevenson 1998), and those of Eriocaulaceae, "poorly differentiated", or with "no exomorphological differentiation" (Stützel 1998). Embryos of the Cyperaceae group are described as being small, but they are more or less differentiated (e.g., see van der Veken 1965). Whatever its state of differentiation, the embryo is small and rather broad.

RAPATEACEAE Dumortier, nom. cons.   Back to Poales

Growth monopodial, plant rosette-forming; Al-accumulators; (culm vascular bundles amphivasal); vessels in leaf?; (mucilage-producing canals +); cuticular wax with wax globules or wax 0, stomatal guard cells dumbbell-shaped; leaves (spirally) two-ranked, (petiole + lamina), sheath open, or asymmetric and conduplicate, axillary uniseriate hairs + [slime-secreting]; inflorescence scapose, axillary, capitate, head subtended by ± spathaceous bracts (bracts 0), units cymose, flowers single, with several basal "bracteoles", large; C basally connate; A basally connate, adnate to C or not, anthers dehiscing by pores, endothecium at apex of anther only, thickening spiral (0); microsporogenesis simultaneous [tetrads tetrahedral]; pollen grains (with encircling aperture), endothecium with spiral thickenings; placentation axile/parietal, style +, stigma capitate; ovules apotropous, (micropyle endostomal), outer integument 3-10 cells across, nucellar epidermal cells often radially elongated [check], suprachalazal area ± massive, funicular obturator +; (antipodal cells several); fruit a septicidal capsule; (seeds carunculate, caruncle chalazal); exo- (and endo)testa with SiO₂, endotestal cells with U-shaped thickenings, cuticular layer between testa and tegmen, tegmen tanniniferous; hypophyll with median sheath lobe, no collar or rhizoids, primary root at most short.

16[list]/94. Tropical South America, West Africa (one species): three subfamilies below. (map: from Givnish 2004a.) [Photo - Epidryos Habit © A. Gentry, Stegolepis Flower © G. Davidse.]

1. Rapateoideae Maguire

Involucral bracts long; middle layerof anther persistent; septal nectaries 0; ovule 1/carpel, ± basal; seeds ovoid-oblongoid, (with papillate apical appendage).

3/29. The Guianas to Bolivia and the Matto Grosso.

[Monotremoideae + Saxofridericioideae]: ?

2. Monotremoideae Givnish & P. E. Berry

Vessels with simple perforation plates; inflorescence axis determinate; ovule 1/carpel, ± basal; seeds white-granulate [muriculate], with flattened apical appendage, ovoid-oblongoid.

4/8. Guiana, upper Rio Negro in Colombia and Venezuela, Maschalocephalus dinklagei in Sierra Leone and Liberia.

3. Saxofridericioideae Maguire

(Leaves petiolate - Saxofridericieae; sheath with auricles - Stegolepis); septal nectaries 0, intra-ovarian trichomes +; ovules few-many/carpel; seeds prismatic, pyramidal, lenticular or crescent-shaped.

9/54: Stegolepis (30+). N. South America, esp. the Guyana Highlands, Panama.

• Rapateaceae are rosette herbs with mucilage in the rosette. Their capitate, scapose inflorescences bear rather conspicuous flowers; the perianth is differentiated into calyx and corolla, there are six stamens, and the anthers dehisce by pores.

Evolution. Divergence & Distribution. Stem-group Rapateaceae are dated to ca 112 mya, the crown group to ca 79 m.y.a. (Janssen & Bremer 2004); ages in Givnish et al. (2004a) are substantially different, being ca 87 and 44.6-33.8 m.y. respectively. Maschalocephalus dinklagei, the only African representative of the family, probably arrived there by long distance dispersal 7.6-6.9 m.y. ago (Givnish et al. 2004a, q.v. for much information on the diversification of the family).

Chemistry, Morphology, etc. Septal nectaries seem to occur in Rapateaceae only in Monotremoideae, but there are also reports of humming bird pollination in other genera (Stevenson et al. 1998a); Vogel (1981) was not sure if nectaries were to be found in the family, and Tiemann (1985) does not mention them. The ovules are described as being crassinucellate (e.g. Rudall 1997), but in some illustrations (Tiemann 1985) they appear to be tenuinucellate.

Some information is taken from Stevenson et al. (1998a); for anatomy, see Carlquist (1966); for ovules and seeds, see Venturelli and Bouman (1988), and for some floral morphology, see Oriani and Scatena (2013).

Phylogeny. Subfamilies and tribes are all well supported at a level of >95% bootstrap, although the [Monotremoideae + Saxofridericioideae] clade has only 74% bootstrap support (Givnish et al. 2004a).

Classification. See Givnish et al. (2004a) for a infrafamilial classification; see also the World Checklist of Monocots.

[[[Eriocaulaceae + Xyridaceae] [Mayacaceae [Thurniaceae [Juncaceae + Cyperaceae]]]] [[Anarthriaceae [Restionaceae + Centrolepidaceae]] [Flagellariaceae [[Joinvilleaceae + Ecdeiocoleaceae] Poaceae]]]]: (1->3),(1->4)-ß-D-glucans +, (isoflavonoids +); cellulose fibrils in the outer epidermal walls of root elongation zone oriented parallel to root axis; trichoblast in atrichoblast/trichoblast cell pair closest to apical meristem; pollen trinucleate; septal nectary 0; ovules lacking parietal tissue.

Evolution. Ecology & Physiology. This clade, along with core Caryophyllales, are the two major foci of the evolution of C₄ photosynthesis (Ehleringer et al. 1997). 24/62 of the independent origins of this syndrome in angiosperms - and nearly all the origins in monocots - occur here (Sage et al. 2011).

Genes & Genomes. Graham et al. (2006) found an accelerated rate of change in the chloroplast genes they sequenced in the Poales - but not in the representatives of Bromeliaceae and Typhaceae (other genes also show accelerated evolution, see G. Petersen et al. 2006b); Smith and Donoghue (2009) found a similar pattern. Givnish et al. (2010b) confirmed that the rate of evolution of the whole plastome has markedly increased in this part of the tree compared to that of most other monocots, although Joinvillea and in particular Flagellaria seem to be exceptions (rate slow-down?).

Chemistry, Morphology, etc. For the distribution of the glucans in both lignified and unlignified cell walls, readily detectable by immunogold labeling, see Trethewey et al. (2005). They are sometimes present in only very small amounts and may be localized according to the thickening of the cell wall (see also Smith & Harris 1999). Rapateaceae were not examined; these glucans are also found in Equisetum (Fry et al. 2009). For the orientation of cellulose fibrils in the root, see Kerstens and Verbelen (2002), sampling still poorer. Sampling for the distribution of trichoblast position is also poor...

[[Eriocaulaceae + Xyridaceae] [Mayacaceae [Thurniaceae [Juncaceae + Cyperaceae]]]]: flavonoids +; leaves spiral; A basifixed; fruit loculicidal, K/T persistent; deletions in ORF 2280 region, full chloroplast accD and mitochondrial sdh4 genes lost.

Evolution. Genes & Genomes. Branch lengths of the ndhF and other genes are notably longer in this part of the monocot tree than anywhere else (e.g. Givnish et al. 2005, 2006b; Saarela et al. 2006).

Chemistry, Morphology, etc. The distribution of the sdh4 gene deletion (see Adams et al. 2002b) is consistent with the topology of the tree presented by Bremer (2002); for the accD gene and ORF 2280 region, etc., especially Hahn et al. (1995) and Katayama and Ogihara (1996).

[Eriocaulaceae + Xyridaceae]: rosette plants; vessel elements with simple perforation plates; SiO₂ bodies 0; leaves also two-ranked; inflorescence capitate, with involucral bracts, terminal (axillary), scapose; (flowers monosymmetric, 2-merous); C clawed, epidermal cells elongated, walls straight; endothecial cells with U-shaped band-like thickenings; pollen more or less spiny; carinal stylar appendages +, vascularized by the dorsal carpellary bundle, styles/stigmas commissural, not vascularized; ovules straight, micropyle endostomal, obturator 0; seed ± ridged, operculum +, tegmic in origin, cuticular layer between testa and tegmen.

Evolution. Divergence & Distribution. Eriocaulaceae and Xyridaceae may have diverged ca 105 m.y.a. (Janssen & Bremer 2004).

The pattern of floral evolution in this clade is unclear. Since both some Eriocaulaceae and some Xyridaceae have very similar carinal nectariferous appendages at the base of or along the style, and unvascularised commissural stylar branches with stigmas (see below), a very distinctive arrangement, these have been placed here synapomorphies for the larger clade, with subsequent reductions.

Chemistry, Morpology, etc. Malmanche (1919) draws phloem and xylem elements intermixed in the root stele of Paepalanthus weddellianus, but not in other taxa; this feature is common in Xyridaceae (Carlquist 1966). Note that Eriocaulaceae have a scape that is bractless (i.e., it is a "true" scape), while that of Xyridaceae may have bracts half way up. An androecium consisting of three antepetalous stamens may have evolved independently and is treated as apomorphic for both Eriocaulaceae-Paepalanthoideae and Xyridaceae. See Oriani and Scatena (2012) for a comparison of reproductive features of the two families.

ERIOCAULACEAE Martinov, nom. cons.   Back to Poales

Root cortex aerenchymatous; (vessel elements with scalariform perforation plates); peduncle with vascular bundles alternately on inside and outside of sclerenchymatous sheath, aerenchyma alternating with lignified strands, photosynthetic tissue in separate packets in t.s.; calcium oxalate crystals +; leaf bundle sheath cells large, without chloroplasts, palisade tissue 0; hairs common, various, on vegetative parts with foot cell and bulbous persistent usually dark colored basal cell; cuticle waxes as aggregated rodlets, stomata variable; leaf sheath not distinct; plant monoecious; receptacle ± flat, scape spirally twisted, bract at base with with closed sheath; flowers small [<6 mm across]; K with single trace, lacking stomata, aestivation open, median K adaxial, (± elongated internode between K and C), C with single trace, scarious, aestivation open; staminate flowers: (A dorsifixed), endothecial cells with complete base plate; tapetum cells uni(bi)nucleate; (microsporogenesis simultaneous); pollen spiraperturate, trinuclear; carpellate flowers: placentation axile; ovules 1/carpel, pendulous, micropyle endostomal, hypostase +; antipodal cyst + [formed by fusion of antipodal cells]; fruit (indehiscent), K/C persistent; endotesta thickened on (anticlinal and) inner periclinal walls, endotegmen tanniniferous (Leiothrix exotestal); radicle 0; n = 9, 15, 20, 25; (ORF 2280 present).

6[list]/1160. Pantropical (to temperate), but esp. Guyana Highlands and S.E. Brasil (map: from Hamann 1961; Giulietti & Hensold 1990; Fl. N. Am. 22: 2000; FloraBase 2004; Trop. Afr. Fl. Pl. Ecol. Distr. 7. 2012). 2 groups below.

1. Eriocauloideae

Plants usu. of aquatic habitats; roots and leaves with aerenchyma; plant dioecious; (K monosymmetric [connate, forming adaxial spathe-like structure]), C free or connate, with black glandular tips; staminate flowers: A 4-6, inner whorl ± adnate to C; pistillode +; carpellate flowers: staminodes inconspicuous; carinal stylar appendages 0 (+, very small), styles/stigmas commissural; testa poorly developed, tegmen tanniniferous.

1-2/420: Eriocaulon (400). Pantropical (to Temperate).

2. Paepalanthoideae

Plants usu. terrestrial; (aerenchyma +); (hairs T-shaped); (flowers perfect); (C 0); staminate flowers: K and C basally fused, (C connate in the middle, free at base by schizogenous slits); C eglandular; A 3, opposite C, (bisporangiate, dithecal; monothecal); pistillode +, nectariferous, (styluli separate); carpellate flowers: (K valvate), (C free); staminodes +; (carinal stylar appendages very small); seeds endotestal, the anticlinal walls with prominent rib-type thickenings.

4/76: Paepalanthus (460), Syngonanthus (200). New World, esp. tropical South America, few Africa.

• Eriocaulaceae are nearly always rosette plants readily recognised by their “pipe-brush” inflorescences. These have slender peduncles that are more or less spirally twisted and ridged or angled, and many small flowers with rather scarious and inconspicuous corollas that are aggregated into dense heads. The base of the inflorescence is surrounded by a single closed leaf sheath.

Evolution. Divergence & Distribution. Stem group Eriocaulaceae are ca 105 m.y.o., the crown group of the former ca 58 m.y.o. (Janssen & Bremer 2004).

Neotropical Paepalanthoideae show much local diversification, and early-divergent taxa are found in the Venezuela-Guayana higlands (Trovó et al. 2013).

Ecology & Physiology. In some submerged species of Eriocaulon CO₂ is taken up from the mud in which they grow via their very well developed root systems (Raven et al. 1998).

Pollination Biology & Seed Dispersal. Although the flowers of Eriocaulaceae are individually rather small and inconspicuous, pollination seems to be by insects here, indeed, with their capitate inflorescences and tiny flowers that nevertheless show a great deal of variation, Eriocaulaceae are the Asteraceae of the monocots. The dark-colored glands on the petals of Eriocaulon may produce nectar. Rosa and Scatena (2003) suggest that in at least some Paepalanthoideae the pistillode (in staminate flowers) and carinal appendages on the gynoecium (carpellate flowers) are nectariferous (see also Rosa & Scatena 2007; c.f. Ramos et al. 2005); the nectary in both cases is made up of much elongated epidermal cells (Oriani et al. 2009).

For a summary of seed dispersal in the family, see Trovó and Stützel (2011).

Genes & Genome. There has been major movement of ribosomal protein and succinate dehydrogenase genes from the mitochondrion in Lachnocaulon (= Paepalanthus), at least (Adams & Palmer 2003).

Chemistry, Morphology, etc. In an anatomical survey of Brazilian Eriocaulaceae, secondary thickening was reported from species of Paepalanthus and Syngonanthus (Scatena et al. 2005). In Tonina (= Paepalanthus) the scape is not twisted, although it is also short; at the base is a sheathing adaxial prophyll that is shortly fused abaxially.

The flowers of Eriocaulaceae may be tiny, yet they show a great deal of variation in meristicity, connation of sepals and petals (this may vary between male and female flowers), presence of perianth glands, etc. (e.g. Giulietti & Hensold 1990). Stützel (1985) found that the morphologically apical glands on the petals of Eriocaulon were displaced by an abaxial outgrowth of tissue and became adaxial-subapical. Coan et al. (2012) described the tetratsporangate anthers as being extrorse, but they seem to be more or less latrorse; the two sporangia of bisporangiate anthers represent a single theca. The microsporocytes are in a single row in each loculus (Coan et al. 2012). When the style is commissural, as in Paepalanthoideae, it is unvascularized; the ovarian appendages of Syngonanthus, etc., are in the position of the style branches of Eriocaulon, and both are vascularized (Coan & Scatena 2004; Rosa & Scatena 2007). Rosa and Scatena (2007) describe staminodial scales opposite to the ovary septae or adnate to the base of the petals in Paepalanthoideae.

For much general information, see Unwin (2004) and from Stützel (1998), for vegetative anatomy, see Malmanche (1919), root anatomy, Stützel (1988), inflorescence and flower, Stützel (1987), for embryology and seed development, Arekal and Ramaswamy (1980), Scatena and Bouman (2001) and Coan and Scatena (2004), for seed and seedling of Paepalanthus, Kraus et al. (1996), for seed morphology, see Giulietti et al. (1984), for floral morphology, see Stützel (1990), Stützel and Gansser (1995), Coan et al. (2012), for floral anatomy, Sajo et al. (1997: petals compound structures) and Rosa and Scatena (2003), and for pollen morphology, see de Borges et al. (2009).

Phylogeny. Support for the monophyly of Eriocauloideae and Paepalanthoideae sampled was good (Unwin 2004: three genes). The more detailed study by Gomes de Andrade et al. (2010: also three genes) provided considerable phylogenetic resolution within the family; the basic phylogenetic structure is [Mesanthemum + Eriocaulon] [Comanthera, Syngonanthus, The Rest]]. Trovó et al. (2013) discussed the phylogeny of Paepalanthoideae.

Classification. Generic limits in Paepalanthoideae are in part unclear, but Syngonanthus needs to be divided (Parra et al. 2010; Gomes de Andrade et al. 2010) and Paepalanthus, already large, expanded somewhat (Gomes de Andrade et al. 2010); see also Trovó et al. (2013). See the World Checklist of Monocots for a listing of species.

XYRIDACEAE C. Agardh, nom. cons.   Back to Poales

(Plant caulescent; monopodial); anthraquinones +; root with cortical stellate cells, stele with xylem and phloem mixed; culm vascular bundles amphivasal; cuticle with insoluble [organic solvent] secretion; mucilage-producing multicellular hairs +; leaf sheath distinct; K monosymmetric, keeled, (2 keeled), the median [abaxial] membranous, (deciduous), C more or less clawed, ephemeral, connate or not: A 3, opposite C, extrorse or latrorse, (free), (sporangia connate), anther wall of the Reduced type; stigma complex and lobed/infundibular; ovules many/carpel, ?micropyle; seed coat testal and tegmic, tegmen mechanical, tanniniferous/resiniferous, (operculum +, chalazal); deletions in ORF 2280 region [?whole family].

5[list]/260. Pantropical to warm temperate. 2 groups below.

1. Xyridoideae

(Plant rhizomatous); stem vascular bundles in a single ring; leaves distichous, equitant, isobifacial [oriented edge on to the stem], (terete), ligulate or not; K lacking stomata, (C enclosing stamen + two half staminodes from adjacent staminodes); (A 6), (endothecium lacking thickenings), staminodia 3, branched and with moniliform hairs on branch ends (hairs 0); tapetal cells binucleate; pollen often binucleate, elliptic (subspherical), surface reticulate and punctate or foveolate, (sulcus U-shaped), (bisulcate), 32-70µm; placentation (intrusive) parietal, basal, axile or free central, carinal stylar appendages 0, styles/stigmas commissural; funicle long, hypostase 0; seeds with apical exotestal scales or fimbriae, endotestal cells thickened; starch grains compound; n = ?8, 9, 13, 14, 16, etc., extensive polyploidy; n = 9, 13, 17; cotyledonary hypophyll bifacial and photosynthetic, hypocotyl and collar rhizoids +.

1/225-300. Pantropical to warm temperate, 150 spp. in Brasil (map: from Hamann 1960; FloraBase 2004; Trop. Afr. Fl. Pl. Ecol. Distr. 7. 2012). [Photo - Xyris Flower, Infructescence © H. Wilson.]

2. Abolbodoideae

Stem vascular bundles alternately on inside and outside of thickish sclerified ring, also scattered in center; leaves spiral (distichous, whether or not equitant, isobifacial - Achlyphila); (inflorescence branched), (open - Achlyphila, some Abolboda), (with 1 or more pairs of opposite bracts along the scape - Achlyphila, Abolboda); P vasculature?, (K polysymmetric), (2 - Abolboda); (A introrse), staminodes 0 (filiform - some Abolboda); pollen spherical, inaperturate, surface spinose, large and small clavate, 49-250µm (22-34µ, clypeate - Achlyphila); placentation axile to parietal, (style solid), (carinal appendages 0 - Achlyphila); ovules anatropous (slightly campylotropous), suprachalazal tissue massive, hypostase +; (exotesta thick-walled, endotesta enlarged), exotegmen thick-walled; n = 8-10, 13, 17.

4/26: Abolboda (22). South America, Guyana Highlands in particular (map: from Campbell 2004).

Synonymy: Abolbodaceae Nakai

• Xyridaceae are rosette plants that often have equitant leaves; they can be recognised best by their inflorescences and flowers. The inflorescences normally bear one or more pairs of bracts along the inflorescence stalk; the flowers are borne in heads and have a conspicuous but ephemeral corolla.

Evolution. Divergence & Distribution. Stem group Xyridaceae are ca 105 m.y. old, the crown group ca 87 m.y. (Janssen & Bremer 2004).

If Achlyphila is sister to other Abolbodoideae, apomorphies for the latter may need to be adjusted.

Pollination Biology. Pollen grains may collect among the hairs on the bifid staminodes of Xyris, perhaps a form of secondary pollen presentation (Remizowa et al. 2012a).

Bacterial/Fungal Associations. The family apparently lacks mycorrhizae.

Chemistry, Morphology, etc. Cury et al. (2012) describe primary thickening in the rhizome of Xyris. Mucilage is secreted by hairs in the leaf axils of Xyris (c.f. Mayacaceae?).

The scape of Xyris is sometimes spirally twisted (c.f. Eriocaulaceae). Pollen is up to 185 µm in diameter in Orectanthe, these are about the largest grains in flowering plants. Placentation is very variable in Xyris, but that of the whole family may be basically parietal. Sajo et al. (1997) show small swellings on the style of Xyris paradisiaca just below the stylar branches. Collar rhizoids are not drawn in Tillich (1994).

Additional information is taken from Carlquist (1960), Kral (1998), Judd et al. (2002) and Campbell (2004), all general. See also Winzieher (1914) and Govindappa (1955), both embryology of Xyris, Malmanche (1918: anatomy), Tomlinson (1969: vegetative anatomy), Sajo and Rudall (1999: leaf anatomy), Tiemann (1985), Kral (1988: Xyris, 1992: other than Xyris), Rudall and Sajo (1999: flower and seed), Scatena and Bouman (2001: seed operculum), Benko-Iseppson and Wanderley (2002: cytology), Campbell (2012: pollen, Achlyphila perhaps multiaperturate), and Stützel (1990), Sajo et al. (1997: Xyris), Campbell and Stevenson (2008: esp. Aratitiyopea), Remizowa et al. (2012a: Xyris), and Oriani and Scatena (2011: Abolboda, 2012: Xyris), all floral morphology, etc.

Phylogeny. There are suggestions that Xyridaceae may not be monophyletic (Michelangeli et al. 2003; Davis et al. 2004, support very weak), thus Abolboda was separate from Xyris (Givnish et al. 2010b), but sampling needs to be improved. Campbell (2004: q.v. for more information) carried out a detailed phylogenetic analysis of morphological variation. Abolboda is particularly distinctive morphologically and may be characterized as follows: stomata also tetracytic; K 2-3, C [3], staminodia filform, tapetum plasmodial, ovules crassinucellate; endotestal cells large, alternating with projecting exotegmic cells; endosperm helobial.

Classification. For the above subfamilial classification, see Campbell (2004); see also the World Checklist of Monocots; for a revision of most Abolbodoideae, see Kral (1992).

[Mayacaceae [Thurniaceae [Juncaceae + Cyperaceae]]]: air canals [?= septate aerenchyma].

MAYACACEAE Kunth   Back to Poales

Marsh plants, growth monopodial; stem with endodermis, vascular bundles alternately on inside and outside; SiO₂ bodies 0; stomatal subsidiary cells with intersecting oblique divisions; leaves flat, apically bidentate, univeined, without a distinct sheath, uniseriate colleters +; flowers axillary, prophyll broad; K with a single trace, C with a single trace, ± clawed, epidermal cells rounded, papillose; A 3, opposite sepals, dehiscing by pores, (sporangia 2), wall of the Reduced type, exothecium +, endothecium lacking thickenings, 2 persistent middle layers; tapetal cells uninucleate; placentation parietal, style with dorsal and ventral carpellary bundles, stigmatic lobes small; ovules 2-30/carpel, straight, hypostase +, obturator +; seed operculum +, endotegmic in origin, exotegmic cells with massive U-shaped lignifications; primary root and cotyledonary hypophyllar sheath 0; n = 8.

1[list]/4-10. Mostly tropical and American (inc. S.E. U.S.A.), 1 sp. from Africa (map: from Hamann 1961; Boutique 1971; Fl. N. Am. 22: 2000; Trop. Afr. Fl. Pl. Ecol. Distr. 7. 2012).

• Mayacaceae are small herbs of marshes looking rather like a club-moss. They have numerous spirally-arranged, apically-toothed leaves borne scattered along the stem and pink to white apparently axillary flowers with a clearly differentiated calyx and corolla.

Chemistry, Morphology, etc. Mayacaceae are vegetatively rather different from many other Poales. There are no vessels in stems and leaves, perhaps associated with the aquatic habitat of the plant (Carlquist 2012a). The vascular bundles on the outside of the endodermal ring are well separated from it (c.f. Eriocaulaceae: Malmanche 1919).

The inflorescence is sometimes described as being terminal, but the flowers examined seemed to be axillary and associated with a broad, adaxial prophyll-like structure (pers. obs.). However, given the association of Mayacaceae with families that have scapose inflorescence with involucral bracts, the inflorescence of Mayacaceae bears re-examination. Sajo (in Sajo & Rudall 2012) noted that all perianth members had a single trace, but that to the petals divided into six. Anthers in some species are monothecal, and the stamens may be basically extrorse (Silveira de Carvalho et al. 2009). The nucellar epidermis is thick basally and the outer layer of endosperm has protein.

Some information is taken from Thieret (1975), Stevenson (1998) and Oriani and Scatena (2012), all general, Tomlinson (1974: stomata), Venturelli and Bouman (1986: ovule and seed), and Endress (2008c: ovule, micropyle endostomal), but the family is poorly known. See also the World Checklist of Monocots.

[Thurniaceae [Juncaceae + Cyperaceae]]: 3-desoxyanthocyanins [1 + 2], luteolin 5-methyl ether +; starch grains pteridophyte-type, amylophilic; leaves 3-ranked, sheaths closed; inflorescence racemose; flowers small, <1 cm across; P = T, scarious; microsporogenesis simultaneous [tetrads tetrahedral], pollen in tetrads, porate; style short, branches/stigmatic surface long; (outer integument ³3 cells across), hypostase +; seeds testal-tegmic; endosperm helobial; chromosomes with diffuse centromeres; phanomer [photosynthetic unifacial cotyledonary hyperphyll] + (0), hypocotyl +, seedling collar inconspicuous, with rhizoids; 3-nucleotide deletion in atpA gene.

Evolution. Divergence & Distribution. This clade can be dated to ca 103 m.y. (Janssen & Bremer 2004).

Roalson et al. (2008) and Hipp et al. (2009) discuss chromosome evolution in the clade. Although diffuse centromeres are a apomorphy for it, only in Carex is there also considerable variation in chromosome number.

Chemistry, Morphology, etc. Both Thurniaceae and Juncaceae have basically racemose (polytelic) inflorescence units (Köbele & Tillich 2001); for possible variation in Cyperaceae, see that family. The inflorescences themselves are often more or less scapose. The nucellus of some Bulbostylis ovules may be only a single cell across (Maria & López 2010). For the atpA gene, see Davis et al. (2004).

THURNIACEAE Engler, nom. cons.   Back to Poales

Root stock upright, trunk-forming or not; flavone C-glycosides +; vessel elements with scalariform perforation plates; stem angled; stem bundles amphivasal [Prionium], SiO₂ also in parenchyma (0 - Prionium); (foliar vascular bundles in pairs, abaxial inverted - Thurnia); cuticular waxes as aggregated rodlets; leaf margin serrate, sheaths?; inflorescence capitate and involucrate or much branched; perianth tube short; tapetal cells?; pollen grains ulcerate, exine granular; (styles separate); ovules 1-few/carpel, ascending, [micropyle zig-zag]; seeds arillate; testa of sclerenchymatous fibres and unthickened cells, (short hairs - Thurnia), tegmen tanniniferous; n =?.

2[list]/4. South Africa and Guyana region, Amazonia (map: see Munro et al. 2001). [Photo - Thurnia Habit, Inflorescence, Prionium - Inflorescence.]

• Thurniaceae can be recognised by their erect, leafy stems, serrate leaves, and pentacyclic flowers with a scarious perianth.

Evolution. Divergence & Distribution. Stem-group Thurniaceae are dated to ca 98 m.y.a., the crown group diverged ca 33 m.y.a. (Janssen & Bremer 2004).

Chemistry, Morphology, etc. The family is poorly known. For the embryology, etc., of Prionium, see Munro and Linder (1999). Tillich (1994) describes the seedling as being similar to that of Juncaceae. See Tiemann (1985) for micropyle type, and Williams and Harborne (1975) for chemistry. Other information is taken from Kubitzki (1998d: general) and Givnish et al. (1999).

Phylogeny. Thurniaceae are sister to Juncaceae + Cyperaceae, with strong support (Givnish et al. 1999; Bremer 2002; Davis et al. 2004), although Oxychloë was not included.

Classification. See the World Checklist of Monocots.

Synonymy: Prioniaceae S. L. Munro & H. P. Linder

[Juncaceae + Cyperaceae]: luteolin +; mycorrhizae 0; chloroplast rpl23 gene absent.

Evolution. Divergence & Distribution. This clade diverged from Thurniaceae ca 98 m.y.a, itself splitting ca 88 m.y.a. (Janssen & Bremer 2004; Besnard et al. 2009b); a highly unlikely crown group age is 39-28 m.y. (Wikström et al. 2001, 2004).

The clade [Juncaceae + Cyperaceae] is notably speciose (Magallón & Sanderson 2001), and the clade including both sedges and grasses is perhaps seven times more speciose than its animal-pollinated sister clade, the bromeliads (sic) (Kay et al. 2006b: supplement not accessable xii.2012; Kay & Sargent 2009).

Bacterial/Fungal Associations. Mycorrhizae appear to be absent, but cluster roots are common. The distributions of parasitic fungi suggest that Cyperaceae and Juncaceae are close (Savile 1979b); for fungal records on the two families, see Tang et al. (2007).

Plant/Animal Interactions. Bugs of the Hemiptera-Lygaeidae-Cyminae and -Pachygronthini are concentrated here (Slater 1976). Clavicipitaceous endophytes have been recorded from some genera, but they are not as common as they are on Poaceae (Clay 1986, 1990); c.f. also the distribution of the parasitic Claviceps itself.

Chemistry, Morphology, etc. See Endress (1995b) for some details of floral morphology.

Phylogeny. Muasya et al. (1998) suggested that Oxychloë (Juncaceae), a cushion plant from Chile, was sister to Cyperaceae, with moderate support, other Juncaceae are paraphyletic, but with with poor support, while Prionium was sister to the whole clade, with good support (see also Muasya et al. 2000: sampling in Juncaceae poor). A study by Plunkett et al. (1995) even placed Oxychloë within Cyperaceae. The relationships of this genus remained unclear (Drábková et al. 2003), although a position in Juncaceae, near Distichia, also a cushion plant, seems likely (Simpson 1995: morphological data; Roalson 2005; see especially Drábková & Vlcek 2007). Part of the problem seems to have been caused by the misidentification of the material from which early molecular samples of Oxychloë were obtained (Kristiansen et al. 2005).

JUNCACEAE Jussieu, nom. cons.   Back to Poales

Plant glabrous (not Luzula); (root hairs from short cells); endodermoid layer +; culm bundles in rings; (vessel elements with scalariform perforation plates); stem rounded; SiO₂ bodies 0 (sand - Juncus); leaves ([spirally] two-ranked), often unifacial [both terete and isobifacial], sheath usu. open, (auricles +), (ligule +); (flowers single); (flowers 2-merous; imperfect); (T large - Marsippospermum); (A 3); tapetal cells uninucleate; pollen grains central in loculus; G shortly stipitate, (placentation parietal), (styles separate), (branches spirally twisted); ovules 1 basal to many central/carpel, micropyle often bistomal, (outer integument 4 cells across), funicular obturator [hairs] and hypostase +/0; seed (?arillate), with (mucilaginous) exotesta and endotegmen; (phanomer 0); n = 3 or more.

7[list]/430: Juncus (300: paraphyletic), Luzula (115). Worldwide, esp. Andes (3 endemic genera), S. South America-New Zealand (2 genera) (map: Vester 1940; Hultén 1961; Frankenberg & Klaus 1980; Balsev 1996; Australia's Virtual Herbarium xii. 2012; FloraBase xii. 2012). [Photo - Juncus Inflorescence, Luzula Flower.]

• Juncaceae are glabrous (Luzula excepted) caespitose herbs that can be recognised by their solid, rounded stems, leaves that are also often rounded and have open sheaths, and pentacyclic flowers with a scarious perianth.

Evolution. Divergence & Distribution. Stem-group Juncaceae are dated to ca 88 m.y., the crown group diverge ca 74 m.y.a, (Janssen & Bremer 2004).

Pollination Biology & Seed Dispersal. The seeds of Luzula are myrmecochorous (Lengyel et al. 2010).

Vegetative Variation. Yamaguchi et al. (2010) show how terete and laterally flattened leaves in Juncus are fundamentally similar, the latter also expressing the DL gene that is responsible for midrib formation in normal bifacial monocot leaves. For unifacial leaves, see also Yamaguchi and Tsukaya (2010).

Chemistry, Morphology, etc. In Luzula stamens are opposite individual tepals (Payer 1857), the median tepal in the outer whorl may be adaxial, and a variety of bract structures are associated with the flower (Eichler 1874). Indeed, inflorescence morphology may repay investigation. For example, Drábková (2010) suggested that that both cymose and racemose inflorescences and flowers with two and no bracteoles were found in Juncus.

Some information is taken from Balslev (1998); for embryology, etc., of some Juncus and Luzula, see Laurent (1904), for anatomy, see Cutler (1969), for some chemistry, see Williams and Harborne (1975), and for floral morphology, see Oriani et al. (2012).

Phylogeny. For a phylogeny, with Juncus perhaps being paraphyletic, see Drábková et al. (2003), Roalson (2005) and especially Drábková (2010). Drábková and Vlcek (2009) found that Juncus trifidus and J. monanthos were separate from the rest.

Classification. For a family monograph, see Kirschner et al. (2002a-c); see also the World Checklist of Monocots. However, the genera - bar Luzula - are a mess (Drábková 2010).

CYPERACEAE Jussieu, nom. cons.   Back to Poales

Aurones, flavonoid sulphates, flavone C-glycosides, tricin, kestose and isokestose storage oligosaccharides [fructans] +; (velamen +); stems solid, angled; SiO₂ bodies smooth, conical, with pointed apices, attached to cell walls; stomatal guard cells dumb-bell shaped; cuticular waxes as aggregated rodlets; leaves (two-ranked; tetrastichous; spiral), sheath with (contra)ligule, (petiole + lamina); inflorescence units spikelets or heads; flowers usu. monosymmetric by reduction; T variously reduced; A (connate), endothecial cells with spiral thickenings; tapetal cells bi-multinucleate; pollen as pseudomonads, (grains 2-celled), with distal pore [ulcus] and with 2 or more lateral apertures, (pontoperculate); (G [2]), (gynophore +); ovule one/flower, basal, parietal tissue to 4 cells across, micropylar/funicular obturator +; fruit an achene, (with bristles, etc.); testa and tegmen thin, ± coalescent, exotesta with SiO₂ bodies, other testal layers fibrous; endosperm cellular, micropylar and chalazal haustoria +; seedling (mesocotyl +), coleoptile +; n = ³5, -> 55, 56; 3 bp 5.8S nrDNA insertion, rps14 gene to nucleus, pseudogene remaining in mitochondrion.

98[list]/5430. World-wide (Map; Hultén 1961; Vester 1940; Australia's Virtual Herbarium xii. 2012). [Photo - Carex Carpellate Inflorescence, Eleocharis Spikes.]

1. Mapanioideae

Phytoliths uncommon; "flowers" = pseudanthia?, imperfect, sterile bracts between stamens and terminal gynoecium; staminate flower: stamens in axils of bracts ["scales"]; (pollen grains central in loculus, spherical, monoporate, sexine thick); (micropyle bistomal, zig-zag - Hypolytrum).

6/166: Mapania (80), Hypolytrum (50). Largely tropical.

Synonymy: Mapaniaceae Shipunov

2. Cyperoideae Beilschmied

Fine roots dauciform; phytoliths common; plants monoecious or polygamous or all flowers perfect; inflorescence branching, with spikelets; (flowers monosymmetric by reduction); T + [= scales, bristles], (connate; inner tepals clawed), 0; A (2) 3, opposite the outer T whorl; pollen grains peripheral in loculi, (spheroidal, monoporate - Coleochloa); gynoecium initiated as an annular primordium, (G 2, superposed, less often collateral); funicle with obturator hairs.

92>/5257: Carex (1776), Cyperus (950), Fimbristylis (250), Rhynchospora (250), Scirpus (200), Scleria (200), Eleocharis (120), Bulbostylis (100), Schoenus (100), Isolepis (70), Schoenoplectiella (50). Worldwide, but esp. N. Temperate.

Synonymy: Kobresiaceae Gilly, Papyraceae Burnett, Scirpaceae Borkhausen, Scleriaceae Berchtold & J. Presl

• Cyperaceae are herbs with solid, sharply three-angled stems and leaves with closed sheaths. The flowers are very reduced and often aggregated into spikes or heads, the perianth, when recognisable, is scarious, and the fruit is an achene.

Evolution. Divergence & Distribution. Stem-group Cyperaceae have been dated to ca 88 m.y., the crown group to ca 76 m.y. (Janssen & Bremer 2004; Besnard et al. 2009b); other ages suggested are ca 100 and 52 m.y. respectively. Escudero et al. (2012) suggest a crown age of (87.6-)83.7(-78.5) m.y. Diversification within Mapanioideae began a mere ca 33 m.y.a., but it began rather earlier within Cyperoideae, ca 77 m.y.a.

Mapanioid sedges are common as fossils (Volkeria messelensis, Caricoidea) in the Eurasian Eocene, where they perhaps grew in wet tropical forests and swamps as do the extant members of this group (S. Y. Smith et al. 2009a, b - c.f. Cyperoideae; for fossils of the family, see also Smith et al. 2010).

Escudero et al. (2012) suggest that crown group Carex can be dated to (54.9-)42.2(-29.7) m.y., major diversification in the genus, which began ca 8 m.y. later, being somewhat linked to decreasing temperatures (especially marked at the end-Eocene ca 34 m.y.a.). Some clades within Carex have speciated quite rapidly, but it is difficult to link any the evolution of any particular morphological feature to diversification here. Although the Siderostictae clade, sister to all other Carex, lacks the wholesale chromosomal rearrangements that characterize the rest of the genus and has only a few species (Escudero et al. 2012), it is unclear why the rearrangements should affect the success of the genus. Divergence within Eleocharis occurred ca 20 m.y.a. (Besnard et al. 2009b).

Ecology & Physiology. Cyperaceae are often particularly common in tundra habitats (ca 8% of the land surface), and include two of the seven major contributors to the biomass there (Gardes & Dahlberg 1996); the other five are core eudicots. About 13% of all species growing in Quebec and Labrador north of 54^o N belong to Carex, and 16% are Cyperaceae (Poaceae are next at 11%), where they can be major components of plant cover especially in wetter habitats (Cayouette 2008; Escudero et al. 2012). Habitats in alpine and other extreme conditions may also be dominated by Cyperaceae. Thus there are some 450,000 km² between 3,000 and 5960 m altitude on the Tibetan plateau dominated by Kobresia pygmaea. This community may be of quite recent origin, reaching its current extent since the spread of the Tibetan empire in the seventh century CE (Miehe et al. 2008, see also Zhou 2001). Cyperaceae-dominated communities were notably extensive during the last glacial maximum north of 55⁰ N (Bigelow et al. 2003).

A number of Cyperoideae-Cariceae and -Rhynchosporeae (but not -Scirpeae) have dauciform roots, roots which develop a dense covering of very long root hairs and overall look rather carrot-shaped; these are believed to help in phosphorous uptake by the plant when growing in phosphorous-poor soils (Shane et al. 2005: some Juncaceae may also have such roots; Playsted et al. 2006). Epidermal cells in such roots are elongated at right angles to the long axis of the root (Shane et al. 2005). The plant secretes citrate chelating agents, etc., into the soil and phosophorous uptake is increased (Playsted et al. 2006). Some species of non-mycorrhizal Carex have distinctive, bulbous-based root hairs (Miller et al. 1999). Many, but not all, tundra-dwelling Cyperaceae, whatever their mycorrhizal status, take up nitrogen predominantly in an organic form (Raab et al. 1996, 1999).

Around about 1,500 species of Cyperaceae carry out C₄ photosynthesis, and this has perhaps six origins in the family, as well as showing some reversals to C₃ (Soros & Bruhl 2000; Besnard et al. 2009b; Bruhl & Wilson 2008; Roalson 2011; Larridon et al. 2011a; Sage et al. 2012). In some aquatic Cyperaceae with submerged leaves C₄ photosynthesis may help increase nitrogen use efficiency (Besnard et al. 2009b; Bruhl & Wilson 2008; Roalson 2011). For the complexity of possible patterns of the evolution and loss of the C₄ pathway and intermediates within Eleocharis, see Roalson et al. (2010); there is only a single major C₄ clade in Cyperus (Reid 2011; Larridon et al. 2013).

Besnard et al. (2008b, 2009b) suggested that evolution of C₄ photosynthesis had occurred within the last ca 19.6 m.y., first appearing in Bulbostylis; genetic changes in the important enzymes phosphoenolpyruvate carboxylase and rbcl may have occurred in parallel. Martins and Scatena (2011) looked at the diversity of Kranz-type morphologies in the family from a developmental point of view.

A few taxa like Rhynchospora anomala are dessication-tolerant and arborescent; their roots, which make up the "trunk" of the plant along with the persistent leaf bases through which the roots run, have a well-developed velamen. Thus Cyperaceae are quite important components of the vegetation of inselbergs where soild are shallow and dry out fast (Porembski 2006).

Waterway et al. (2009) discuss ecological diversification in Cariceae; there are widespread wetland species and often more geographically restricted forest taxa. Clones of Carex curvula may persist for 2,000 years or so in the Alps despite climatic fluctuations (Steinger et al. 1996: growth rate changes probably not important).

Bacterial/Fungal Associations. Cyperaceae, like other plants in the tundra habitat (see above), often lack mycorrhizae (but c.f. Muthukumar 2004; Miller at al. 1999 for mycorrhizae in Carex). However, in Tibet and Greenland, at least, Kobresia species are ectomycorrhizal (Gao & Yang 2010). Largely ascomycetous fine endophytes are commonly found in Cyperaceae from tundra habitats (Higgins et al. 2007), and are more prevalent than arbuscular mycorrhizal fungi. They may be members of Clavicipitaceae, elsewhere especially prominent on Poaceae-Poöideae (Schardl 2010). Dauciform roots (see above), dark septate hyphae and/or endomycorrhizae may all be found in the one species, whether in the same or a different locality (Michelsen et al. 1998; Gao & Yang 2010).

Smuts (Ustilaginales) are very diverse on Cyperaceae (Kukkonen & Timonen 1979; Savile 1979b).

Pollination Biology & Seed Dispersal. Although Cyperaceae are normally thought of as being a wind-pollinated clade, there have been some transitions to insect pollination (Wragg & Johnson 2011 and references).

Fruit dispersal mechanisms are very varied, including water, wind (e.g. the bristles surrounding the fruits of Eriophorum), animals (both epi- and endozoochory), and ants (Allessio Leck & Schütz 2005: also seed dormancy and germination requirements).

Genes & Genomes. Carex is notable for the wide variation in chromosome number it shows because of chromosome fission, fusion and translocation facilitated by the diffuse centromeres of the genus (Hipp et al. 2011). Genome size has, however, remained almost constant (Chung et al. 2012); genome size and chromosome number are negatively correlated in diploid taxa, and although polyploids tend to have larget genomes than related diploids, they do not have absolutely large genomes (Lipnerová et al. 2013).

Chemistry, Morphology, etc. In grasses (q.v.), at least, the coleoptile is part of the cotyledon. For inflorescence morphology, see Reutemann et al. (2012: individual variables listed); branching can be from the axils of prophylls, and/or from collateral or superposed meristems. Zhang et al. (2004) suggested that spikelets in Schoeneae, at least, were sympodial, however, those of Cyperoideae as a whole are indeterminate (Vrijdaghs et al. 2005c, 2008 [Schoenus], 2010 [esp. Cyperoideae]). Studies by Guarise et al. (2012) emphasized the diversity in development pathways that produced superficially similar capitate inflorescence in Cyperus; relatively few developmental changes could also produce substantial diversity in mature inflorescence morphology.

For the literature on the possible pseudanthial nature of some flowers in Cyperaceae-Mapanioideae, see Bruhl (1991); he noted that the "foliar" structures in the taxa he studied were outside the stamens, so they probably represented perianth parts (see also Vrijdaghs et al. 2004a; Richards et al. 2005, esp. 2006: flowers of Exocarya scleroides [Mapanioideae] pseudanthial). The distinctive hairs of Eriophorum (Cyperoideae) arise centripetally on a perianth ring-primordium (Vrijdaghs et al. 2004b).

Scirpus sylvaticus has a relatively unspecialised flower in which the three stamens and the carpels are opposite the outer perianth members (Vrijdaghs et al. 2005a); the scirpoid pattern is perhaps that to which more derived morphologies in Cyperoideae can be related (Vrijdaghs et al. 2009). In general, the stamens are shown as being opposite the outer perianth whorl (Bruhl 1991), the angles of the gynoecium (Goetghebeur 1998) or the style-stigma (Larridon et al. 2011b), all consistent with a flower in which members of the whorls alternate and the absence of the inner stamen whorl is of no consequence. The median carpel in Carex is shown as being adaxial (Eichler 1875), i.e. in the inverted position (see also Spichiger et al. 2004, but c.f. Reynders & Vrijdaghs et al. 2012).

Pollen apertures in Carex have a very thin underlying intine that in interapertural areas is much thickened, i.e., the reverse of the normal condition (Halbritter et al. 2010). As Vrijdaghs et al. (2011) note, it is difficult to talk about carpels in Cyperoideae since the gynoecium develops from an annular primordium - on top of which there may be two or three (rarely even four) branched styles; when there are two styles, there has not been any obvious fusion of two carpels or reduction of one (Reynders & Vrijdaghs et al. 2012). Although I have placed "gynoecium initiated as an annular primordium" as an apomorphy for Cyperoideae, Reynders and Vrijdaghs et al. (2012) note that it is also found in Luzula, and elsewhere, as in Poaceae.

For a vast amount of information, see Bruhl (1995), for further general information, see Naczi and Ford (2008). For the prophyll, see Blaser (1944), for embryo morphology, see van der Veken (1965: hundreds of species); for inflorescence morphology, see Eiten (1976) and Nijalingappa and Goetghebeur (1989: Ascopholis, bristle = axis), for floral morphology, see Bruhl (1991) and Vrijdaghs et al. (2006), for pollen, see van Wichelen et al. (1999), Nagels et al. (2009), Coan et al. (2010) and Furness and Rudall (2011), for the gynophore, etc., see Vrijdaghs et al. (2005b), for phytoliths, see Piperno (2006), for chromosome number and evolution, see Hipp (2007), Roalson (2008), Roalson et al. (2008a), and Hipp et al. (2009), for a nrDNA insertion, see Starr et al. (2008a), and for ovule and seed development, see Nijalingappa and Devaki (1978) and Coan et al. (2008).

Phylogeny. Mapanioideae and Cyperoideae are monophyletic (Simpson et al. 2003, esp. 2008; Hinchcliff & Roalson 2013). Within Cyperoideae, Trilepideae are sister to all the rest (Muasya et al. 2009a); a clade [Sclerieae + Biesboeckelereae] has moderate support as sister to the rest in a supermatrix analysis, and then the topology [Schoeneae [Rhynchospora [clade including Carex and Scirpus + clade including Eleocharis, Isolepis and Cyperus]]] (Hinchcliff & Roalson 2013). Cyperus is massively paraphyletic (e.g. Muasya et al. 2002; Larridon et al. 2011a, b; Hinchcliff & Roalson 2013), and Larridon et al. (2013) show that C₄ members of the clade are monophyletic and embedded in a paraphyletic C₃ group, although relationships along the spine of the C₄ clade were for the most part little supported. For other relationships, see Hinchcliff and Roalson (2013), for the relationships of Carpha and other Schoeneae, see Zhang et al. (2007); for relationships within Rhynchosporeae, see Thomas et al. (2009); and for relationships around Eleocharis, see Hinchcliff et al. (2010) and Roalson et al. (2010).

Within the large and complex Cariceae, relationships are beginning to be resolved (Reznicek 1990 and associated papers; Yen et al. 2000; Roalson et al. 2001; Starr et al. 2006). Carex is paraphyletic, as has been demonstrated by several studies (see Yen & Olmstead 2000; Starr et al. 1999, 2004; Waterway & Starr 2008; King & Roalson 2008: use of nrDNA problematic; Starr & Ford 2009; Escudero & Luceño 2009; Gehrke et al. 2010: resolution at base of genus poor). Starr et al. (2008b) suggested that there are four major clades around Carex - [Uncinia, Kobresia, Cymophylla, some Carex] [Schoenoxiphium, some Carex] [Carex subgenus Vignea], and [Carex subgenus Carex, etc.], however, details of the relationships of Carex s.l. are unclear (Hinchcliff & Roalson 2013). Conventional wisdom in which a highly compound inflorescence is the plesiomorphic condition for Carex, taxa with simple spicate branches being derived, perhaps several times, seems the exact opposite of what actually happened (Ford et al. 2006). Similarly, species of Carex believed to be intermediate between that genus and Uncinia, with its hooked inflorescence axis protruding through the apex of the perigynium (prophyll), seem not to be (Starr et al. 2008b: support not strong). Again, evolution is not necessarily complex -> simple.

Naczi (2009) discussed the use of morphological characters in phylogenetic analyses; this is tricky because of the highly derived nature of cyperaceous flowers.

Classification. Carex is paraphyletic (see above) and genera like Kobresia, Cymophyllus, Uncinia and Schoenoxiphium should be included in it (or some species of Carex will have to be moved). For a general evaluation of generic limits in Cypereae, see Muasya et al. (2009b); Cyperus is to include about thirteen genera (see also Muasya et al. 2002; Hinchcliff et al. 2010; Larridon et al. 2011a, b, 2013; Reid 2011); Eleocharis is also to be slightly expanded (Hinchcliff et al. 2010). For pre-lapsian nomenclature, etc., see Goetghebeur (1985); see also the World Checklist of Monocots (Govaerts et al. 2007 is a printed version of this). T. M. Jones provides a Carex interactive identification key.

[[Anarthriaceae [Restionaceae + Centrolepidaceae]] [Flagellariaceae [Joinvilleaceae + Ecdeiocoleaceae] Poaceae]]]: flavones +; primary cell wall also with(1-3,1-4)-ß-D-glucans; sieve tube plastids with cuneate and other less densely packed crystals; (chlorenchyma with peg cells [c.f. arm cells of some Poaceae?]); leaves two-ranked, with sheath; bracteoles 0; flowers small [<1 cm across]; P = T, membranous; endothecial cells with ± helical/girdle-like thickenings; pollen monoporate, annulate ["ulcerate"], wall scrobiculate [minute pores penetrating tectum and foot layer]; style branches long, stigmas plumose; ovule 1/carpel, apical, straight; seedling with collar rhizoids.

Evolution. Divergence & Distribution. Divergence of the Poacaeae and Restionaceae clades occured ca 109 m.y.a., the stem group age is ca 112 m.y. (Janssen & Bremer 2004: c.f. topology). Wikström et al. (2001: again c.f. topology) suggest a stem group age of only 49-45 m.y.

This is a notably speciose clade (Magallón & Sanderson 2001) with well over 11,000 species, although the diversification rate is lower than that of Cyperales. However, there is considerable asymmetry in clade size within this clade, with most species belonging to Poaceae, the second most species-rich family (Restionaceae) having only some 520 species, less than 1/20 the species in Poaceae (Chase 2004; c.f. Linder & Rudall 2005 for diversification); this is discussed further under Poaceae below.

Chemistry, Morphology, etc. For the flavonoids of Anarthriaceae, Restionaceae and Ecdeiocoleaceae, see Williams et al. (1997a); the variation is complex and needs to be re-evaluated in light of the current position of the last family.

Linder and Ferguson (1985) discuss variation in pollen morphology. Flagellariaceae have "multicellular papillae" on their stigmas (Appel & Bayer 1998), whether these are receptive in the same way as the multicellular branches of, say, Poaceae, needs clarification. Note that in Poaceae, although the style is hollow, the pollen tubes grow between elongate transmitting cells of these multicellular branches (Lersten 2004). The ovule is scored as lacking any parietal tissue and so being tenuinucellate and the pollen as being trinucleate for the whole group by Givnish et al. (1999, c.f. Appel & Bayer 1998 for these characters). Joinvilleaceae in particular are largely unknown.

Information on the ORF 2280 region is taken from Hahn et al. (1995) and Katayama and Ogihara (1996: Ecdeiocoleaceae not included). For the loss of the rpoC1 gene, see Morris and Duvall (2010).

Phylogeny. An analysis of 26S rDNA suggested that Dasypogonaceae might be part of this clade, being very closely linked with Ecdeiocoleaceae, Anarthriaceae and Centrolepidaceae (Neyland 2002b), slightly less so with the one member of Restionaceae included. However, data from atpB, rbcL, 18S, etc., have not confirmed this grouping (see e.g. Givnish et al. 2010b), and Dasypogonaceae are probably sister to Arecaceae (q.v.). Davis et al. (2004: very weak support) found Flagellaria to group with Mayacaceae, etc., rather than with the other Poales.

However, although the composition of this clade now seems settled, relationships within in are still somewhat unclear. Bremer (2002) found a sister group relationship between Ecdeiocoleaceae and Poaceae, as had Harborne et al. (2000), although the latter did not include Joinvilleaceae and Flagellariaceae in their study. A combined morphological and molecular (mitochondrial and chloroplast genes) analysis placed Flagellariaceae, Ecdeiocoleaceae and Poaceae in an unresolved trichotomy (Michelangeli et al. 2002, esp. 2003), a not dissimilar result to that obtained by Davis et al. (2004). Graham et al. (2005) obtained a set of relationships [Flagellariaceae [Restionaceae [Ecdeiocoleaceae + Poaceae]]], perhaps a branch length or sampling problem. Using two chloroplast genes, Marchant and Briggs (2007) found strong support for a sister group relationship between Joinvilleaceae and Ecdeiocoleaceae (both genera were included), and these relationships were also found by Saarela and Graham (2010), but only in Bayesian analyses. More recently, Givnish et al. (2010b: plastome sequences) found good support for the [Ecdeiocoleaceae + Poaceae] clade, and this topology is tentatively preferred here.

[Anarthriaceae [Centrolepidaceae + Restionaceae]]: root hairs originating from any epidermal cells; culm with parenchymatous sheath, palisade chlorenchymatous tissue, and sclerenchymatous cylinder, vascular bundles inside; chlorenchyma with peg cells; plant dioecious; flowers imperfect; staminate flowers: A 3, opposite inner P, dorsifixed; pistillode 0; carpellate flowers: staminodes 0; phanomer [photosynthetic unifacial cotyledonary hyperphyll] +; loss of rpoC1 gene.

Chemistry, Morphology, etc. See Malmanche (1919) for vegetative anatomy; he described the stomata as what would be called brachyparacytic.

ANARTHRIACEAE D. F. Cutler & Airy Shaw   Back to Poales

(Flavonol glycosides +); root hairs lignified; SiO₂ 0; stomata in grooves; leaves ligulate; culm branched; staminate flowers: pollen operculate; carpellate flowers: G opposite outer P; ovules?, hypostase +; seed coat?; endosperm type?, embryo?; ?collar rhizoids; n = 6, 9, 11; ORF 2280 +, trnL gene with 3bp deletion and 5bp insertion.

3[list]/11. West Australia (map: from FloraBase 2004). [Photo - Anarthria Staminate & carpellate inflorescences © D. Woodland]

Evolution. Divergence & Distribution. Stem-group Anarthriaceae are dated to ca 96 m.y., the crown group to ca 55 m.y. (Janssen & Bremer 2004).

Chemistry, Morphology, etc. The three genera are rather different. Anarthria lacks palisade tissue, a sclerechymatous cylinder and parenchyma sheath in the culm (or it could be interpreted as having a cylinder towards the middle of the culm, with scattered vascular bundles outside), it has equitant isobifacial leaves, stomata in grooves, a deciduous spathe, and n = 11. Cronquist (1981) suggested that the flowers had bracteoles. Hopkinsia has G 1, with long branches on the style; the fruit is a nut with a fleshy pedicel and persistent perianth, and n = 9; the cotyledon is apparently not photosynthetic. Lyginia has fructans, the culm is unbranched, there are crystals and druses, the stamens are connate, the seeds are minutely spiny with a central hyaline flange, and n = 6. Hopkinsia and Lyginia have a culm with subepidermal chlorenchyma separated from cortex by parenchymatous and sclerenchymatous rings, leaves reduced to scales, and microverrucate pollen. Stigma papillae in Anarthria? Microsporogenesis?

Much general information is taken from Linder et al. (1998) and Briggs and Johnson (2000). See also Cutler and Airy Shaw (1964: anatomy), Linder (1984: African members of the family), and Linder and Rudall (1993: esp. Anarthria).

Phylogeny. The phylogenetic structure of the family is [Anarthria [Hopkinsia + Lyginia]] (Briggs et al. 2000; papers in Meney and Pate 1999).

Classification. Putting the three genera in three separate families seems a bit much, no hierarchical information being conveyed by this move, although the three are morphologically quite distinct. Indeed, Linder et al. (2000) even suggested that these genera belonged to Restionaceae, albeit perhaps sister to the rest - they (but not Anarthria itself) have the distinctive culm anatomy of that family, and Lyginia has starch in the embryo sac, like Restionaceae (Hopkinsia is unknown).

Synonymy: Hopkinsiaceae B. G. Briggs & L. A. S. Johnson, Lyginiaceae B. G. Briggs & L. A. S. Johnson

[Centrolepidaceae + Restionaceae]: plant ± glabrous; (foliar epidermis with long and short cells); anthers bisporangiate, monothecal; pollen pore not annulate, margin irregular; cells of nucellar epidermis anticlinally elongated; embryo sac with compound starch grains esp. surrounding polar nuclei, antipodal cells ± proliferating, persistent.

Phylogeny. The position of Centrolepidaceae with respect to Restionaceae has been uncertain (e.g. Linder et al. 2000), most studies unfortunately concentrating on either the Australian or African Restionaceae rather than the broader studies that were needed to solve the problem. A position sister to Restionaceae was possible (Linder & Caddick 2001) as well as one within the family (Bremer 2002: support weak). In more recent studies Centrolepidaceae and Restionaceae were sister taxa in parsimony analyses of trnK and trnL-F, while in Bayesian analysess, and also in rbcL analyses, the relationships [Restionoideae [Sporadanthoideae [Leptocarpoideae + Centrolepidoideae]]] were recovered (Briggs & Linder 2009; Briggs et al. 2010); the latter set of relationships seems more likely. It is noteworthy that the pollen apertures of Australian Restionaceae in particular are like those of Centrolepidaceae, a larely Malesian-Australasian group (Chanda 1966).

CENTROLEPIDACEAE Endlicher, nom. cons.   Back to Poales

Plant ± caespitose; vascular bundles in culm on either side of thickened cylinder (not Gaimardia), palisade tissue 0; SiO₂ ?0; epidermis with hairs and papillae; leaves unifacial, (ligulate); plants monoecious; inflorescence scapose, capitate and with inflorescence bracts, or spicate; P 0; staminate flowers: A 1-2; pollen trinucleate; carpellate flowers: G [1-14(-45)]; (parietal tissue 1 cell across), nucellar cap 0; antipodals usu. binucleate; fruit dehiscing abaxially or indehiscent; endotegmen alone persistent, tanniniferous; embryo conoid; (phanomer 0), first seedling leaf with lamina, chlorenchymatous cells isodiametric or palisade; n = 10.

3[list]/35. Hainan, IndoChina and Malesia to New Zealand, S. South America (Gaimardia) (map: from Ding Hou 1957; Hamann 1960; van Balgooy 1984; FloraBase 2004). [Photo - Gaimardia Habit and Close-up, Centrolepis Habit.]

• Centrolepidaceae are rather small more or less caespitose herbs. The inflorescence is scapose and spicate or capitate and involucrate.

Evolution. Divergence & Distribution. Estimates of the age of the Centrolepidaceae clade range from 45-97 m.y. depending in large part exactly where it is placed in the tree (Janssen & Bremer 2004).

Chemistry, Morphology, etc. Cutler (1969) emphasized the fact that the root hairs arose from one side of the epidermal cell and that the root lacked a pericycle. He suggested that the peg cells of Centrolepidaceae and Restionaceae might be rather different, peg cells s.s. perhaps being absent in the former. Also, whether or not the family has SiO₂ bodies needs confirmation.

There has been some discussion as to whether Centrolepidaceae have a flower or pseudanthium; Sokoloff et al. (2009b) reject the latter proposition. Sokoloff et al. (2010; see also Hamann 1962a; Remizowa et al. 2011) interpret the inflorescence of Centrolepis as being a racemose spikelet, not cymose. Hou (1957) described the anthers as being 1- or 2-celled. The separate carpels sometimes become more or less fused, the result being something that looks like a syncarpous gynoecium - or, in Centrolepis itself, the gynoecium is definitely syncarpous, and although the carpels there appear to be more or less one on top of each other, that is because of developmental gymnastics resulting in the greater development of one side of the receptacle (Sokoloff et al. 2009b). The ovule is described by Hamann (1975) and Cooke (1998) as being weakly crassinucellate and also as having a megasporocyte that lacks a parietal cell; although cells in the nucellar epidermis may have divided, this seems unlikely from the illustrations in Hamann (1962a).

RESTIONACEAE R. Brown, nom. cons.   Back to Poales

Root hairs usu. persistent, lignified; rhizome with endodermoid sheath; culm with lignified chlorenchymatous cells lining substomatal cavities [protective cells]; leaves much reduced, (sheath closed); (plant monoecious); inflorescence as spikelets; outer T hooded [?how common], (P 0), staminate flowers: (anthers tetrasporangiate, e.g. Harperia), tapetal cells 1-4-nucleate, pollen central in loculus; pollen (binucleate), with coarse granules [exine fragments] on pore; pistillode 0; carpellate flowers: P variable; staminodes 0; G opposite outer P, (only 1 fertile), common style short or 0, stimatic receptive cells on multicellular branches; ovule (micropyle endostomal - Willdenowia, some Leptocarpus), (parietal tissue ca 1 cell across - Alexgeorgea, ?Hypodiscus), suprachalazal zone ± massive, hypostase +; antipodal cells proliferating; exotesta persistent, ± thick-walled; (cotyledon not photosynthetic), hypocotyl and collar at most small, collar rhizoids +, first seedling leaf with lamina; 28 kb chloroplast genome inversion +/- [latter - Desmocladus, Elegia?].

58[list]/500 - four groups below. Africa (inc. Madagascar), Hainan and Vietnam to Australia, New Zealand, Chile (map: from Good 1974; Trop. Afr. Fl. Pl. Ecol. Distr. 7. 2012). [Photos - Collection. Dovea tectorum is properly Chondropetalum tectorum.]

1. Restionoideae Bartling

Flavonols, non-hydrolysable tannins, myricetin derivatives +, flavones less diverse; pollen grains with pores 4-10 µm across, margins annulate [raised], (thickened foot layer +); n = 16, 20.

11-16/350: Africa south of the Sahara, Madagascar.

1a. Restioneae Bartling

SiO₂ bodies often in parenchyma sheath, not in sclerenchyma cylinder; chlorenchyma cells radially elongated; styles 1-3, often widely separate; (fruit a soft-walled nut); young seed coat tanniniferous.

3-8/300: Restio (95), Ischyrolepis (48), Elegia (50), Thamnochortus (35). Madagascar, Africa south of the Sahara, especially the Cape Region. [Photo - Elegia, Habit.]

Synonymy: Elegiaceae Rafinesque

1b. Willdenowieae Masters

SiO₂ bodies usually in sclerenchyma cylinder only; ridges of sclerenchyma often alternate with vascular bundles, chlorenchyma cells often radially short and squat (lignified chlorenchyma cells extending from ridges); [G 2], styles branches 2, (basally connate); proliferating antipodals?; fruit a nut, often with elaiosomes [fleshy pedicels]; young seed coat not tanniniferous.

8/50: Anthochortus (15). The Cape region of South Africa.

[Sporadanthoideae + Leptocarpoideae]: flavonols rare, except quercetin, non-hysrolysable tannins rare, flavones diverse, sulphated flavonoids +; chlorenchymatous cells palisade; pollen grains with pores 8-25 µm across, not annulate, irregular, thickened foot layer 0 [c.f. also Centrolepidaceae!]; cotyledon not photosynthetic [ca half the genera], seedling culm internodes elongated, leaves terete; n = 6, 7, 9, 11, 12.

2. Sporadanthoideae Briggs & Linder

Myricetin +; spikelets often 0, flowers solitary and with bracteoles.

3/31: Lepyrodia (22). Australia and New Zealand.

3. Leptocarpoideae Briggs & Linder

Flavones, sulphated flavonoids + [(8-hydroxyflavonoids, e.g. gossypetin]; chlorenchyma interrupted by pillar cells [radiating ± palisade-like and ± lignified cells of sclerenchyma sheath] (0), (sclerenchymatous bundle girders opposite outer vascular bundles +); protective cells 0, (elongated, thick walled epidermal cells +).

28/117: Chordifex (20). Hainan and Vietnam to Australia, New Zealand, Chile (Apodasmia).

• Restionaceae are sometimes quite large rush-like herbs with very much reduced leaves; the flowers are small, imperfect, but usually with a perianth, and they are usually aggregated into spikelets.

Evolution. Divergence & Distribution. Stem-group Restionaceae are dated to ca 96 m.y., the crown group to ca 74 m.y. (Janssen & Bremer 2004).

There are ca 350 spp. of Restionaceae in the Cape region, diversification beginning in the late Eocene-early Oligocene some 43-28 m.y. before present (Hardy et al. 2004a; Linder & Hardy 2004; Hardy et al. 2008). Some diversification in Australian Restio may be associated with the aridification of the Nullarbor Plain some 14-13 m.y.a. separating what became eastern and western clades (Crisp & Cook 2007)

Ecology & Physiology. Restionaceae can be locally dominant in oligotropic conditions, whether wet or dry. Thus Restionaceae replace Poaceae in the graminoid layer in the nutrient-poor soils of the fynbos vegetation of the Cape Floristic region (Bell et al. 2000). The habitats they prefer are often subject to seasonal fires, and some species, sprouters, accumulate starch in their rhizomes, while others, non-sprouters, reproduce by seeds (c.f. Ericaceae). The rootlets of Restionaceae are also described as being capillaroid, with dense and exceptionally long root hairs, although there are other distinctive root morphologies (Lambers et al. 2006); Cyperaceae and Proteaceae growing in similar phosphorous-poor environments develop analagous structures that are believed to facilitate phosophorous uptake. T. L. Bell et al. (2000) suggested that the total root length of the grasses tested was considerably greater than that of Restionaceae, although the dense root hairs of the latter were not taken into account. [What is the relationship with lignification of root hairs?]

Pollination Biology & Seed Dispersal. Myrmecochory is common in the African Restionoideae-Willdenowieae, the nutlets having fleshy funicles that attract ants (Briggs & Linder 2009).

Chemistry, Morphology, etc. The culm has subepidermal chlorenchyma separated from the cortex by parenchymatous or sclerenchymatous rings; these may not be strictly comparable (Cutler 1969) and so may not be an apomorphy for the family.

Information is taken from Borwein et al. (1949) and Krupko (1962), both embryology, Kircher (1986; he does not draw the guard cells as being dumb-bell-shaped), Linder et al. (1998: general), Meney and Pate (1999), Linder and Caddick (2001: esp. seedlings), Ronse Decraene et al. (2001a, 2002b: floral development, much variation) and Newton et al. (2002: seeds). Williams et al. (1998) and Harborne et al. (2000) describe flavonoid patterns in the family. For Peter Linder's "Intkey thingy" on African Restionaceae - 2,000 pictures - see http://www.systbot.unizh.ch/datenbanken/restionaceae/.

Phylogeny. The variation in the presence of the 28kb chloroplast genome inversion within Restionaceae is remarkable (Michelangeli et al. 2003); is the family polyphyletic?! For phylogenetic relationships, see Briggs et al. (2010).

Classification. For the classification of Restionaceae and characterization of the subfamilies, see Briggs and Linder (2009); Leptocarpoideae have been pulverized. Linder and Hardy (2010, see also Linder 1985) provide generic characterisations and an enumeration of the species of Restionaceae-Restioneae in southern Africa, although the limits of Restio itself are still unclear.

[Flagellariaceae [[Joinvilleaceae + Ecdeiocoleaceae] Poaceae]]: primary cell walls with branched mixed-linkage glucans; leaf blade with cross veins, ligule +; inflorescence branches with adaxial basal swellings; endothecial cells with complete base plate thickenings; nucellar cap +, suprachalazal zone massive; fruit indehiscent, fleshy; cotyledon not photosynthetic.

Evolution. Ecology & Physiology. Net venation, animal-dispersed propagules, tolerance of shady habitats, and preference for well drained amnd fertile substrates are linked in in some members of this group (Givnish et al. 2005, 2010b).

Chemistry, Morphology, etc. Data on polysaccharide wall composition (mixed-linkage glucans) can be found in Smith and Harris (1999: Joinvilleaceae not included) and Popper and Fry (2004: detected in members of Poaceae and Flagellariaceae, but not in Restionaceae, Juncaceae, and Cyperaceae [the only other Poales examined], nor in any other vascular plants).

For the scoring of cross veins in the leaf, see Soreng and Davis (1998). For alternating long and short cells, see Stevenson in Michelangeli et al. (2003) and Briggs in Givnish et al. (2010b). In the interpretation of floral morphology of Ecdeiocoleaceae I follow Rudall et al. (2005a) and especially Whipple and Schmidt (2006); see also the discussion after Poaceae. For thickening of the endothecial cell walls, see Manning and Linder (1990); these are difficult to categorize in Joinvilleaceae and Ecdeicoleaceae.

FLAGELLARIACEAE Dumortier, nom. cons.   Back to Poales

Stem apices dichotomise; flavonols +; endodermal cells radially elongated; culm solid; SiO₂ associated with vascular bundles only; neighbouring cells of stomata with oblique divisions; prophylls lateral; leaves with terminal tendril, ?auricles, sheath also closed; bracteole 0; T members with single trace [?level], whitish, soft; microsporogenesis simultaneous; style solid; micropyle endostomal, outer integument ca 4 cells across, parietal tissue 1 cell across; embryo sac bisporic, eight nucleate [Allium-type], antipodal cells numerous; fruit a drupe, seed coat adnate to pericarp; outer periclinal wall of exotesta persisting; n = 19; ORF 2280 present?; seedling with collar hairs +, coleoptile at most short.

1[list]/4. Palaeotropics, to the Pacific Islands (map: van Steeenis & van Balgooy 1966; Heywood 1978). [Photo - Flower]

• Flagellariaceae are robust, climbing or scrambling rather grass-like plants that can be recognised by their leaves that terminate in a sensitive tendril by which the plant is attached to its support. The rather large, paniculate inflorescences have many small, perfect flowers.

Evolution. Divergence & Distribution. Flagellariaceae may be ca 108 m.y. old (Janssen & Bremer 2004: but note the topology).

Chemistry, Morphology, etc. Flagellaria indica is reported to have a dichotomising stem apex, the vegetative leaves of aerial shoots lacking axillary buds (Tomlinson & Posluszny 1977), however, Kircher (1986) interprets the dichotomy as being a stem apex plus modified axillary branch.

Since the seed coat is adnate to the fruit wall, I suppose the fruit is a caryopsis.... Is the coleoptile part of the cotyledon, as in Poaceae (Takacs et al. 2012), or the first foliage leaf? There is disagreement as to whether or not the ORF 2280 gene is present (c.f. Hahn et al. 1995 and Katayama & Ogihara 1996).

Some information is taken from Subramanyam and Narayana (1972) and Rudall and Linder (1988), both embryology, Tillich (1996b: seed and seedling), Appel and Bayer (1998: general), Tillich and Sill (1999: general), Sajo et al. (2007: style), and Sajo and Rudall (2012: floral morphology).

[Joinvilleaceae [Ecdeiocoleaceae + Poaceae]]: SiO₂ bodies cubic; epidermis with microhairs; foliar epidermis with long and short cells [latter SiO₂-containing] throughout; guard cells dumb-bell-shaped; fusoid cells [large colourless cells in central mesophyll] +; culm hollow [level?]; endothecial cells with girdle thickenings [?Poaceae]; stimatic receptive cells on multicellular branches; first seedling leaf lacking lamina [possible]; 28 and 6.4 kb chloroplast genome inversion.

Evolution. Divergence & Distribution. This clade may have originated ca 103 m.y.a. (Janssen & Bremer 2004: Flagellariaceae not associated with it); it diversified only ca 90 m.y.a.

Chemistry, Morphology, etc. The microhairs are multicellular in Joinvilleaceae and some Poaceae. Ecdeiocoleaceae, a small family of small herbs, has recently been placed in this clade (see below); if their seedlings have leaf blades, they may provide a valuable source of data on epidermal anatomy.

See Endress (1995b) for some details of floral morphology. For chloroplast genome inversions, see Doyle et al. (1992); the 6.4 kb inversion has been reported in Ecdeiocoleaceae (Michelangeli et al. 2002, 2003; Marchant & Briggs 2007). For a trnT inversion, see Morris and Duvall (2010), for endothecial thickening, see Sajo and Rudall (2012).

JOINVILLEACEAE Tomlinson & A. C. Smith   Back to Poales

Microhairs multicellular; leaf vernation plicate, auricles or ligules +; flowers perfect; T green, rather dry, outer T hooded; microsporogenesis ?simultaneous; pollen grains peripheral in loculus; carpels with lateral bundles, style hollow; ovule parietal tissue?; fruit a drupe, 1-3-seeded, T persistent; endotegmen tanniniferous; n = 18; rps14 gene to nucleus, pseudogene remaining in mitochondrion; starch grains compound; first seedling leaf lacking lamina.

1[list]/2. Malay Peninsula to the Pacific (map: from van Steenis & van Balgooy 1966; Newell 1969). [Photo - Habit, Flower.]

• Joinvilleaceae are robust, grass-like plants with plicate leaves and terminal panicles of small, perfect, brownish flowers.

Evolution. Divergence & Distribution. Joinvilleaceae may be some 90 m.y. old (Janssen & Bremer 2004); they are reported as fossils from New Zealand, although they do not grow there now (Lee et al. 2001).

Chemistry, Morphology, etc. The outer tepals may have only a single trace (Newell 1969), although Sajo and Rudall (2012) describe both whorls of tepals as being supplied by three vascular traces.

Some information is taken from Bayer and Appel (1998: general).

[Ecdeiocoleaceae + Poaceae]: flowers monosymmetric by reduction, imperfect; pollen with operculum, wall without scrobiculi, with intraexinous channels; fruit 1-seeded.

ECDEIOCOLEACEAE D. F. Cutler & Airy Shaw   Back to Poales

SiO₂ as sand; vessels?; stomata in grooves down culm; ?microhairs; epidermal long and short cells 0; leaves reduced, sheath closed, auricles +; plant monoecious; culm branched, inflorescence branch swellings?, with spikelet-like heads; flowers monosymmetric; 2 P ± conduplicate and keeled, 4 P flat; staminate flowers: (A 4 - Ecdeiocolea); pollen with operculum; carpellate flowers: carpels with lateral bundles, style hollow; ovule apical, area of enlarged cells near embryo sac; embryo sac tetrasporic, 16-celled [Drusa type: ovule, etc. - all Ecdeiocolea]; fruit achene or loculicidal capsule; ?perisperm +; exotestal cells large; n = ca 24, 32, 33; seedling?

2[list]/3. S.W. Australia (map: from FloraBase 2004).

Evolution. Divergence & Distribution. Stem-group Ecdeiocoleaceae are dated to ca 89 m.y. before present, the crown group diverge ca 73 m.y. before present (Janssen & Bremer 2004).

Chemistry, Morphology, etc. The illustration in Linder et al. (1988) shows leaves on the inflorescence axis with quite well developed blades. There is no evidence of differentiated long/short epidermal cells (B. G. Briggs, in Givnish et al. 2010b).

In Georgeantha the two adaxial calyx members are keeled, in Ecdeiocolea the differentiation is somewhat less pronounced. The flowers of Ecdeicolea are monosymmetric; the four stamens probably represent the outer whorl plus the adaxial stamen of the inner whorl (Rudall et al. 2005a). The exotesta is very differently thickened in the two genera, and the fruits are quite different.

Some information is taken from Briggs and Johnson (1998), Linder et al. (1998), Rudall (1990: embryology), and especially Rudall et al. (2005a: floral development, fruits).

POACEAE Barnhart, nom. cons.//GRAMINEAE Jussieu, nom. cons. et nom. alt.   Back to Poales

(Aerial branching + [?level]); vesicular-arbuscular mycorrhizae +; 3 desoxyanthocyanins, flavone 5- and C-glycosides, tricin, flavonoid sulphates, (cyanogenic glycosides) +; primary cell wall rich in arabinoxylans, pectin 10³%, xyloglucans lacking fucose; lignins acylated with p-coumarates [?level]; sieve tube plastids also with rod-shaped protein bodies, P-proteins 0; arm and fusoid cells +; cuticle waxes as aggregated rodlets; stomatal subsidiary cells conical to dome-shaped; microhairs bicellular; leaves pseudopetiolate, ligulate, (± fringed with hairs), with a broad blade, vernation supervolute(-plicate), midrib +; T with two adaxial outer members distinct, abaxial smaller; A centrifixed [?level]; pollen grains central in loculus; gynoecial rudiment annular, (G open in development), stigmas 3[?]; ovule one/flower, central, amphitropous or hemianatropous, micropyle endostomal, funicle short; fruit an achene, the tegmen closely adherent to pericarp [= caryopsis], hilum long; testa not persistent, hilum long [reverses]; peripheral layer of endosperm meristematic, endosperm hard, embryo lateral, long, well differentiated, cotyledon lateral, cotyledon = scutellum + coleoptile, plumule terminal, embryonic leaf margins overlapping; primary root 0, collar [epiblast, the ligule of the cotyledon] conspicuous; expansion of the inverted repeat [level?], chloroplast genome with [third!] trnT inversion in the single-copy region, only 17 introns [that in clpP absent], loss of accD, ycf1, ycf2 genes, duplication of AP1/FUL genes [= FUL1 and FUL2], rpoC2 gene insert, rps14 gene to nucleus, pseudogene remaining in mitochondrion, intergenomic translocation of chloroplast rpl23 gene; ADP-glucose pyrophosphorylase in cytosol.

707/11,337. Thirteen subfamilies below. Worldwide (map: from Vester 1940; Hultén 1961). [Genera List]

1. Anomochlooideae Potzdal

Silica bodies elongated transverse to the long axis of the leaf; microhairs 75-150 µm long [i.e., huge], basal cells constricted part way up; (leaves spiral - Streptochaeta); pseudopetiole with an apical (and basal) pulvinus, midrib projecting on both surfaces, (ligule 0); inflorescence branches cymose, two "bracts" along each branch unit, two more "bracts" below each flower; flowers perfect, protogynous; P 2 (3) + 3; or flowers spirally arrranged along racemose axis, with several spiral "bracts" below each flower, = T, possibly 3 + 3, the latter coriaceous; A (4 - Anomochloa, 3 members of the inner whorl), centrifixed, basally connate, not dangling, anthers ± latrorse, wall development of the Reduced type, endothecium lacking thickenings; (microsporogenesis simultaneous - Streptochaeta); style solid, stigma not plumose; nucellar cap 4-5 cells across [Anomochloa]; (testa lignified, persistent - Anomochloa); embryo small [Anomochloa], (scutellar cleft +), (epiblast +), (embryonic leaf margins not overlapping); 21bp [long] subrepeats in rpoC2 gene insert; n = 11, 18; first seedling leaf lacking lamina.

2/4. Central America to S.E. Brasil, scattered, forests (map: from Judziewicz et al. 1999).

Synonymy: Anomochloaceae Nakai, Streptochaetaceae Nakai

[Pharoideae [Puelioideae [PACMAD + BEP clades]]] / the spikelet clade: inflorescence without inflorescence bracts, spikelets +, laterally compressed, racemose, pedunculate, with two basal glumes [sterile bracts = spikelet bract + prophyll], flowers two-ranked, plane of symmetry of flower relative to spikelet horizontal; flower protandrous, with lemma and palea [?= bract and 2 adaxial connate outer-whorl T], lodicules 3 [= inner whorl T/C; esp. in staminate flowers], median member adaxial; x = 12; 1 bp deletion in the 3' end of the mat K gene, loss of rpoC1 gene, 39bp subrepeats in rpoC2 gene insert.

2. Pharoideae L. G. Clark & Judziewicz

Inner bundle sheath multi-layered; intercostal epidermis with files of fibres alternating with files of normal long cells; microhairs 0; leaves resupinate, lateral veins oblique; plants monoecious; inflorescence and spikelets with uncinate microhairs; spikelets 1-flowered; (lodicules 0); staminate flowers: A (4-)6, anthers basifixed, latrorse, wall of the Reduced type, endothecium lacking thickenings [both Pharus]; carpellate flowers: style hollow; micropyle bistomal [Pharus]; (scutellar cleft +), epiblast +; coleoptile [= sheathing base of cotyledon] with blade.

4/13. Pantropical, in forests (map: from Judziewicz 1987; Judziewicz et al. 1999). [Photo - Flower.]

Synonymy: Pharaceae Herter

[Puelioideae [[PACMAD + BEP clades]] / the bistigmatic clade: phytoliths saddle-shaped; spikelets several-flowered, disarticulating above the glumes; anthers versatile[?]; pollen grains peripheral in loculus; stigmas 2, two orders of stigmatic branching; 15bp ndhF insertion.

3. Puelioideae L. G. Clark, M. Kobay., S. Mathews, Spangler & E. A. Kellogg

Culm hollow; (minute bracts subtending inflorescence branches); spikelets with several flowers, basal flowers staminate or sterile, apical pistillate or perfect; ?lodicules; A 6; (stigmas 3); embryo small, otherwise unknown; seedling leaf unknown.

2/11. Tropical Africa (map: from Emmet Judziewicz, pers. comm.).

[PACMAD + BEP clades]: fructan levels low, (benzoxazinoids, ergot alkaloids [latter synthesized by endophytes] +); arm cells 0, fusoid cells 0; foliar cross veins 0; pseudopetiole 0; flower type?; C/lodicules 2; A 3, wall of the Monocot type; G 2, styles separate; antipodal cells proliferating; scutellar cleft +, epiblast +; x = 12; genome duplication, 15 bp insertion in ndhF gene, disease resistance by the Hm 1 gene.

[Aristidoideae [Panicoideae [[Arundinoideae + Micrairoideae] [Danthonioideae + Chloridoideae]]]] / PACMAD clade: C₄ photosynthesis prevalent; (ligule of hairs); phytoliths dumb-bell-shaped; lemma awned; starch grains compound; mesocotyl internode elongated, epiblast 0, embryonic leaf margins meeting; extension of ndhF gene from the short single copy region into the inverted repeat.

4. Aristidoideae Caro

(Plants annual); (spikelet cylindrical), with one flower; lemma awn trifid, with basal column, or 3 (1); callus pubescent; (scutellar cleft 0); n = 11, 12; germination flap +.

3/365: Aristida (250-290), Stipagrostis (50). Warm temperate, few in Europe.

[Panicoideae [[Arundinoideae + Micrairoideae] [Danthonioideae + Chloridoideae]]]: 6 bp insertion in the 3' end of the mat K gene [?whole clade]

5. Panicoideae Link

(Plant annual); (culms branched); (fusoid cells +); microhairs often with slender, elongated thin-walled apical cells [panicoid type]; (mesophyll differentiated into palisade and spongy tissues), (chlorenchyma cells lobed [c.f. arm cells]); culms usually solid; (pseudopetiole +), (midrib complex); (inflorescence bracts +); spikelet 2-flowered, lower flower staminate or sterile [gynoecial cell death caused by Tasselseed2], development basipetal, rachilla 0; plane of symmetry of flower relative to spikelet vertical; ?lemma awned; (style +); (spikelet disarticulation below the glumes); hilum punctate; (epiblast 0), embryonic leaf margins overlapping; starch grains simple; 5 bp insertion in the rpl16 intron; n = (5, 7) 9 [Paniceae], 10 (11, 12, 14); (epiblast +), germination flap +; rps14 pseudogene lost.

212/3316: Paspalum (330), Cenchrus (105: inc. Pennisetum), Andropogon (100), Panicum (100), Dicanthelium (55), Eriachne (40). Tropics to temperate.

Synonymy: Andropogonaceae Martinov, Arundinellaceae Herter, Cenchraceae Link, Ophiuraceae Link, Panicaceae Berchtold & J. Presl, Paspalaceae Link, Saccharaceae Berchtold & J. Presl, Zeaceae A. Kerner

[[Arundinoideae + Micrairoideae] [Danthonioideae + Chloridoideae]]: ?

[Arundinoideae + Micrairoideae]: (hilum short).

6. Arundinoideae Burmeister

Microhairs with elongated, slender, thin-walled apical cells [panicoid type]; callus pubescent; (embryonic leaf margins overlapping); n = 6, 9, 12.

19/46. Temperate to tropical, hydrophytic to xerophytic.

Synonymy: Arundinaceae Döll

7. Micrairoideae Pilger

(Annual plants); culms solid or hollow; leaves (spirally arranged - Micraira); (lemma awn 0); starch grains simple, embryo small; n = 10; germination flap +; (C₄ photosynthesis - Eriachneae).

9/188: Isachne (100), Eriachne (35). Tropics.

[Danthonioideae + Chloridoideae]: lemma bilobed, awned from the sinus; hilum punctate.

8. Danthonioideae Barker & Linder

Plant annual, with C₃ photosynthetic pathway; (stomata with parallel-sided subsidiary cells)); prophylls bilobed [?distribution]; lemma awn trifid, or 3 awns; lodicules with microhairs; bases of styles well apart; embryo sac with haustorial synergid cells; n = 6, 7, 9.

17/281: Danthonia (100), Rytidosperma (90). Widespread, esp. Southern Hemisphere, few Southeast Asia-Malesian.

9. Chloridoideae Beilschmied

Plants tolerate drought, high saline conditions; C₄ PCK subtype (phosphoenolpyruvate carboxykinase) + (0); microhairs with ± hemispherical and thick-walled apical cells and long base cell, latter with internal membranes and secretory [chloridoid type], also panicoid type; embryo with an epiblast; 4 bp insertion in the rpl16 intron; n = (6-8) 9, 10.

130/1721: Eragrostis (300), Muhlenbergia (155), Sporobolus (160), Chloris (55). Tropical to warm temperate, more or less dry environments especially in Africa and Australia.

Synonymy: Chloridaceae Berchtold & J. Presl, Cynodontaceae Link, Eragrostidaceae Herter, Lepturaceae Herter, Pappophoraceae Herter, Spartinaceae Link, Sporobolaceae Herter, nom. inval., Zoysiaceae Link

[Ehrhartoideae [Bambusoideae + Poöideae]] / BEP clade: endosperm softness gene +, ?embryo short; x = 12.

10. Ehrhartoideae Link

(Silica bodies elongated transverse to the long axis of the leaf); (arm cells + - Oryzeae), (fusoid cells +); (longitudinal walls of epidermal cell straight); (microhairs 0); (ligule a ring of hairs); flowers perfect or not; spikelet with two basal sterile florets, apical flowet fertile; A (1-)6, style branches separate almost from the very base; n = (10, 15); (first seedling leaf without lamina - Oryzeae), (roots at scutellar node - Ehrharta).

17/111: Oryza (20), Leersia (20). Widespread, esp. S. hemisphere.

Synonymy: Ehrhartaceae Link, Oryzaceae Berchtold & J. Presl

[Bambusoideae + Poöideae]: ?

11. Bambusoideae Luersson

Woody; culm development biphasic, lignification and branch development in 2^nd phase, branched; fusoid cells +, arm cells +, strongly asymmetrically invaginated; microhairs with elongated, slender, thin-walled cap cells [panicoid type]; (multiple buds per node); leaves pseudopetiolate, articulated, culm leaves different from the others, largely sheaths, outer ligule +; flowering synchronized, plants monocarpic; (inflorescence bracts +); lodicules 3, vascularized; A (2-)6(-140), (basally connate), (endothecial cells with ± U-shaped thickenings); (stigmas 1-3); (ovules ategmic, unitegmic); (fruit a berry); first seedling leaf without blade; much polyploidy.

116/1439. Tropical to temperate, often in forests (map: see Judziewicz et al. 1999; Sungkaew et al. 2009).

11a. Arundinarieae Ascherson & Graebner

Rhizomes slender; culms hollow, branch development basipetal; midrib complex; n = 24.

26/533: Fargesia (60), Sasa (40-60), Phyllostachys (55), Arundinaria (50). More or less temperate E. U.S.A., eastern Asia, also Africa, scattered, ± montane.

11b. Bambuseae Dumortier

Rhizomes massive; branch development acropetal or bidirectional; midrib complex; n = (10), 20, (22), 23, 24, etc.

84-101/1470. Chusquea (200), Bambusa (120), Merostachys (50), Schizostachyum (50). Tropical to (warm) temperate.

Synonymy: Bambusaceae Berchtold & J. Presl, Parianaceae Nakai

11c. Olyreae Martinov

± Herbaceous; culm development uniphasic, branching slight; epidermal silica cells usu. with cross-shaped silica bodies in the costal zone and crenate [olyroid] silica bodies in the intercostal zone [not Buergersiochloa]; leaves not articulated, culm leaves not very different from the others, outer ligule 0; flowering rarely synchronized and monocarpic; plant monoecious; spikelets unisexual, dimorphic, 1-flowered, often dorsiventrally compressed, one-flowered, rachilla extension 0; (lodicules 0); n = 7, 9, 10, 11, (12).

21/120 Pariana (35). Central and South America and Africa, also New Guinea (Buergersiochloa).

Synonymy: Olyraceae Berchtold & J. Presl

12. Poöideae Bentham

Temperate habitats, (plants annual); Epichloë endophytes pervasive; aerial branching at most rare; fructose oligosaccharides in stem; root epidermal cell division forming trichoblast/atrichoblast pair asymmetric; longitudinal walls of epidermal cells straight [?level]; culms hollow; lemma usually with 5 nerves, (awned); lodicules at most slightly vascularized; style branches separate almost from the very base; (postament +); (endosperm with some non-starch soluble storage polysaccharides); embryo small; n = (2, 4-13); duplication of the ß-amylase gene.

177/3850. Largely North Temperate.

1. Brachyelytreae Ohwi

Stomata subsidiary cells with parallel sides; n = 11.

1/3. Eastern Asia, E. North America.

[Nardeae [Phaenospermateae + The Rest]]: primary inflorescence branches 2-ranked; embryo lacking scutellar cleft, embryonic leaf margins non-overlapping.

2. Nardeae Koch

Lodicules 0; style and stigma 1; n = 10, 13.

2/2. Europe.

Synonymy: Nardaceae Martynov

[Phaenospermateae + The Rest]: microhairs 0 (+ - some Stipeae); (stomata subsidiary cells with parallel sides); n = 7, chromosomes "large".

3. Phaenospermateae

21 bp insertion in in rpl32-trnL; n = 7, 12.

7/11. Central to East Asia, also Australia, Mexico, Balkans, Caucasus; scattered.

The Rest.

Fructan levels often high; style solid [Triticum].

169/3833: Festuca (470: inc. Lolium), Poa (200), Stipa (300), Calamagrostis (230), Agrostis (220), Elymus (150), Bromus (100). Largely North Temperate.

Synonymy: Aegilopaceae Martynov, Agrostidaceae Berchtold & J. Presl, Alopecuraceae Martynov, Anthoxanthaceae Link, Avenaceae Martynov, Bromaceae Berchtold & J. Presl, Chaeturaceae Link, Coeleanthaceae Pfeiffer, Cynosuraceae Link, Echinariaceae Link, Festucaceae Sprengel, Glyceriaceae link, Holcaceae Link, Hordeaceae Berchtold & J. Presl, Laguraceae Link, Loliaceae Link, Melicaceae Martynov, Miliaceae Link, Phalaridaceae link, Phleaceae Link, Sesleriaceae Döll, Stipaceae Berchtold & J. Presl, Triticaceae Link

• Poaceae can be recognised by their leaves that have long, usually open sheaths and ligules at the sheath-lamina junction, round and often hollow stems/culms, and inflorescences whose basic unit is a spikelet. Individual flowers are small, lacking an obvious perianth and with a gynoecium that usually has two plumose stigmas and a single ovule. In the dry, achenial fruit (often called a caryopsis), the rather large embryo is lateral, lying next to the seed coat.

• The large tribe Andropogoneae, with almost 1,100 species, can be distinguished from all other grasses because they have paired spikelets.

Evolution. Divergence & Distribution. The family may have originated in Africa (Bouchenak-Khelladi et al. 2010c) or South America (Bremer 2002) - either way, it seems to have been on Gondwanan continents. Stem-group Poaceae are dated to ca 89 m.y., the crown group to ca 83 m.y. (Janssen & Bremer 2004: Streptochaeta included, see also Bremer 2002; dates in Wikström et al. 2001 are far younger). Bouchenak-Khelladi et al. (2009, 2010a) suggest that crown grasses are (97-)76(-43) m.y.o., while Bouchenak-Khelladi et al. (2010c) estimated that the crown group was ca 72 m.y., within divergence within Anomochloideae beginning (86-)68(-53) m.y.a.. Puelioideae diverged (76.8-)58(-57.6) m.y.a. (Bouchenak-Khelladi et al. 2010a).

Bouchenak-Khelladi et al. (2009, see also 2010a) estimated that the spikelet clade originated in the Late Cretaceous, (95-)74(-73) m.y.a., while Bouchenak-Khelladi et al. (2010c) gave an estimate of (83-)67(-55) m.y. Fossil spikelets assignable to the [PACMAD + BEP] clade are known from the Palaeocene-Eocene boundary, about 55 m.y. before present (Crepet & Feldman 1991). Molecular evidence suggests that the bulk of the family, i.e. the [PACMAD + BEP] clade, may have begun to diversify (53.8-)51.9(-59) m.y.a. (Wu & Ge 2011: 95% c.i.). Most other estimates are broadly similar. Thus Vicentini et al. (2008) suggested ages of (60-)52(-44) m.y., Kim et al. (2009: MAD members not included) dated it to 67.8-50 m.y. (see also Bouchenak-Khelladi et al. 2010a), and Bouchenak-Khelladi et al. (2010c) estimated ages of (55-)52(-50) m.y., a bit younger than Bouchenak-Khelladi et al. (2010a). Other estimates like that Bouchenak-Khelladi et al. (2010a) are (60-)52(-44) m.y., while Z. Peng et al (2013) suggest ages of 64.5-53.9 m.y. These dates are broadly in line with that of the age of a genome duplication in Poaceae 70-50 m.y.a. (Blanc & Wolfe 2004; Schlueter et al. 2004; Paterson et al. 2004; Kim et al. 2009).

The PACMAD clade itself may have diversified rather later, some 45-37 m.y.a. (see Bouchenak-Khelladi et al. 2010a for other dates), although Bouchenak-Khelladi et al. (2010c) suggest a younger age of (34-)28(-22) m.y. Stem Aristidoideae date from (38-)29(-9) m.y.a., crown dates from (25.5-)20.3(-15.9) m.y.a., but much diversification there is considerably younger (Bouchenak-Khelladi et al. 2010a; Cerros-Tlatilpa et al. 2011, q.v. for other estimates).

Bouchenak-Khelladi et al. (2009, 2010a, c) suggested that the BEP clade began to diversify at the end of the Palaeocene about 53 m.y.a., while Magallón et al. (2013) give a much younger age of around 38.5 m.y.. Wu and Ge (2011) offer an age of (53.8-)51.9(-50) m.y., Bambusoideae and Poöideae diverging (51.6-)47(-40.8) m.y.a., while dates in Z. Peng et al (2013) are ca 48.6 and 47.8-46.9 m.y. respectively. Bambusoideae diversified some (48-)29(-26) m.y.a. in the middle Oligocene (Bouchenak-Khelladi et al. (2009, 2010a, c; see also Wu & Ge 2011: separation of Phyllostachys and Bambusa [35.6-]22.5[-9] m.y.a.), with the very diverse Old World members of Arundinarieae being a mere 15 m.y.o. Tropical Old and New World bamboos may have diverged 24.8-40.2 m.y.a. (Burke et al. 2012: c.f. other ages there).

However, Poinar (2004) proposed that Programinis burmitis, found fossil in deposits from the Early Cretaceous of Myanmar some 100-110 m.y.a., represented an early bambusoid grass. To others, it seemed to have some vegetative features that are common in Poaceae, but not the distinctive features of the family and so was unlikely to be included there (Smith et al. 2010). Nevertheless, in a recent more detailed analysis of P. laminatus, Poinar (2011) affirmed that the silica bodies, etc., indeed supported a placement in Poaceae, particularly in Poöideae, so suggesting an age for that subfamily about twice that of other estimates (see below). Although recent estimates of the age of these amber deposits are younger, no earlier than Early Cenomanian at (99.4-)98.8(-98.2) m.y. (Shi et al. 2012), they are still surprisingly old.

The age of grasses (as well as that of other monocot groups, not to mention the animals, both vertebrates and insects, associated with them) is also called into question, although somewhat less dramatically, by the discovery of well-preserved phytoliths of types to be found in the PACMAD and BEP clades in coprolites of sauropod dinosaurs from the Late Cretaceous 67-65 m.y. of central India (Prasad et al. 2005), and this would date the origination of the PACMAD-BEP clade to some 85-80 m.y.a.; such fossils have been identified as Ehrhartoideae-Oryzeae (Prasad et al. 2011). Indeed, the fossil pollen genus Graminidites occurs widely (but not in Australia) in the Late Cretaceous (Srivastava 2011), even if at least locally not in association with dinosaurs. Although the enigmatic Late Cretaceous mammalian sudamericid gondwanatherians had hypsodont teeth and there is a record of a Cretaceous hadrosaurian dinosaur with carbon isotope ratios that suggests that it might have been eating C₄ plants (Prasad et al. 2005; Bocherens et al. 1994), the origin of C₄ grasses - and most other C₄ plants - is usually put in the middle of the Tertiary (see below). To summarize: Dates from different lines of evidence are apparently irreconcilably in conflict (Vicentini et al. 2008).

The Poaceae group of families has been described as being notably speciose (Magallón & Sanderson 2001), but there is considerable asymmetry in clade size within this larger clade, with the great majority of species belonging to Poaceae themselves, which may be seven times more speciose than their animal-pollinated sister clade (Kay & Sargent 2009: surely a stunning underestimate?). However, even within Poaceae there are three species-poor clades that are successively immediately sister below the PACMAD and BEP clades (to add to the two to three more such clades successively sister below the family). Thus any foci of diversification are within the PACMAD and BEP clades (c.f. Linder & Rudall 2005; Smith et al. 2011; and especially Bouchenak-Khelladi et al. 2010c). Schranz et al. (2012) thought that there was a lag time between a genome duplication that characterized the family and its subsequent diversification, but they thought that the two might be linked.

Hodkinson et al. (2008) discuss increases of diversification rates in Poaceae in the context of a supertree; there seems to have been one increase when true spikelets developed, and several others elsewhere in the family (see also Bouchenak-Khelladi et al. 2010c). The herbaceous habit and annual life cycle appear to be correlated with species richness (Salamin & Davies 2004; Smith & Donoghue 2008); the speciose Bambusoideae are woody; Poöideae are largely temperate; C₄ photosynthesis has arisen many times in the PACMAD clade, and clades with C₄ photosynthesis tend to be more speciose than their sister clades with C₃ photosynthesis; Chloridoideae tolerate drought and saline conditions, etc. However, Soreng and Davis (1998) in particular show how difficult it is to be sure of the position on the tree of many of the characters mentioned above.

Ecology & Physiology. Bouchenak-Khelladi et al. (2010c: Puelioideae not included; Givnish et al. 2010b) suggested that the family may initially have been forest dwellers, and both the species-poor largely forest-dwelling basal clades and the stem PACMAD clade, largely plants of more open habitats, had diverged by the end of the Cretaceous. For good summaries of the ecology of grasses and grasslands, see Coupland (1993a, b), White et al. (2000) and Gibson (2009). The global extent of grassland, including savanna, is 52.5x10⁶ km², or somewhere between 41-56x10⁶ km², that is, 31-43% of the total land surface area (excluding Greenland and Antarctica: Gibson 2009)). Other estimates are lower, ca 20% of the earth's surface (Hall et al. 2000; Sabelli & Larkins 2009), the figures depending in part on the definition of grassland. Grasses in the Great Plains alone cover slightly over 3x10⁶ km², the Campos Cerrado ca 2x10⁶ km² (see also the map: rather virulent green, more or less pure grassland, olive green, communities with trees and shrubs as well as substantial grass; endpapers in Coupland 1993a, b; esp. White et al. 2000, Map 1, for more details; see also Clade Asymmetries).

Grasses and C₄ photosynthesis.

There are some suggestions that C₄ photosynthesis persisted through the Mesozoic (Keeley & Rundel 2003 for literature). However, its appearance in clades of extant angiosperms is a Tertiary phenomenon. All told, only 7,500 species of flowering plants have the C₄ photosynthetic syndrome, and of these about 4,500 are grasses, where they make up about three quarters of the almost 5,900 species of the PACMAD clade (Sage et al. 1999, 2012; Grass Phylogeny Working Group II 2011). Within grasses, there has been massive parallelism in the acquisition of C₄ photosynthesis, with some 22-24 separate origins of this feature in the PACMAD clade (e.g. Kellogg 2000; Roalson 2011: 12-19 transitions; Christin et al. 2008a, 2009 b; Vicentini et al. 2008; Cerros-Tlatilpa & Columbus 2009 and Christin & Besnard 2009 [both Aristidoideae]; Grass Phylogeny Working Group II 2011; Sage et al. 2011, 2012; Morrone et al. 2012).

The adoption of C₄ photosynthesis is associated with well-known anatomical changes, such as closer spacing of the veins, the development of a sheath of chloroplast-rich cells around the vascular bundles, etc. - the Kranz anatomical syndrome (see Pengelly et al. 2011 for vein spacing). The mechanisms of C₄ photosynthesis and the anatomies associated with it are very variable in Panicoideae, where C₄ photosynthesis may have evolved up to eight times there alone (Kellogg 2000; Giussani et al. 2001; Christin et al. 2007a, 2009a). Interestingly, both origins of and reversals from C₄ photosynthesis may be clustered, although reversals are not very common (Vicentini et al. 2008; for reversals, see also Ibrahim et al. 2009). The relatively uncommon C₄ PCK subtype (phosphoenolpyruvate carboxykinase) may be basal in Chloridoideae, being subsequently lost and reacquired (Christin et al. 2009b; Christin et al. 2010a: reversals; Ingram et al. 2011b: a reversal that wasn't). A few intermediates in which there is C₂ photosynthesis are known from the family (Monson & Rawsthorne 2000; Bauwe 2011 for references). Note that although anatomy may be used to characterize subtypes of C₄ photosynthesis, the correlation of anatomy and photosynthetic pathway may not be that good (Ingram 2010), and the typology needs to be revisited (E. A. Kellogg, pers. comm.).

These parallelisms perhaps reflect an underlying change that faciltated subsequent "independent" acquisitions of the C₄ photosynthetic pathway (Grass Phylogeny Working Group II 2011: gene duplication not involved; Williams et al. 2012; see Marazzi et al. 2012). Parallelisms may be at the level of particular amino acids being substituted, similar changes occurring independently in the phosphoenolpyruvate carboxylase gene in grasses (Christin et al. 2007a, esp. b, 2009a). In particular, a mutation to serine at position 780 seems to have occurred in all plants with C₄ photosynthesis (Bläsing et al. 2000; see also Brown et al. 2011 for C₄ parallelisms between grasses and Capparidaceae; Grass Phylogeny Working Group II 2011), and functionally important parallelisms are also found in rbcL (Christin et al. 2008b). Lateral transfer of genes may also have been involved in putting together a C₄ pathway. The sequential transfer of genes over a period of millions of years from quite unrelated grasses, perhaps via movement of genes from pollen of a grass that lands on the stigma of a plant that it cannot pollinate, may explain the nature of the C₄ pathway in Allopteropsis (Panicoideae). No other genes seem to be involved, and a taxon embedded in the clade has ordinary C₃ photosynthesis (Christin et al. 2012). This is difficult to get one's head around...

Christin et al. (2013) have suggested particular anatomical changes that facilitated the transition to C₄ photosynthesis in grasses. They suggest that veins - or at least bundle sheaths - became closer in the common ancestor of the PACMAD + BEP clade - and a high proportion of vascular bundle sheath tissue facilitated this transition. C₄ photosynthesis did not develop in the BEP clade, because the outer bundle sheath cells subsequently became smaller, but it did in the PACMAD clade because they became larger (although they were sometimes lost there, but then the inner sheath cells became dramatically larger). Finally, mesophyll cells were sometimes lost in the PACMAD clade (Christin et al. 2013). In a less elaborate analysis, Griffiths et al. (2012) suggested that bundle sheath proliferation had begun before any change in vein densities.

Grasses and Grasslands, Fire and Forest.

This discussion largely applies both to C₄ grasses and to the more cold tolerant grasses, most of which are C₃; the evolution of cold tolerance is discussed below. Understanding the ecological relationship between grasslands and woodland over time is important. Grasses of the [PACMAD + BEP] clade predominantly prefer more open habitats, although most Bambusoideae are woody (3 m or more tall) and forest dwellers. Open habitat grasses, probably C₃, appear in the Middle Eocene ca 42 m.y.a., and may have become locally dominant (Strömberg 2011); they diversified taxonomically in North America in the early Oligocene ca 34 m.y.a. (Strömberg 2005). However, the factors that favoured the initial development of grasslands, caused the clustering of origins and losses of different photosynthetic mechanisms, and were involved in the great spread and expansion to dominance of late Miocene C₄ grasslands, remain unclear (see also Tipple & Pagani 2007; Jacobs et al. 1999; Sage & Kubien 2003; Fox & Koch 2004; Osborne & Beerling 2006; Bond 2008; Westhoff & Gowick 2010). As we will see, some combination of temperature, atmospheric CO₂ concentration, fire and water stress is now emphasized (Bond et al. 2003; Edwards & Still 2008; Edwards 2009; Strömberg & McInerney 2011; Christin et al. 2011b). Indeed, grasslands may be very sensitive to changing climates, in some reconstructions of the effect of the current increase in CO₂ in the atmosphere, the spread of C₃ grasslands is quite extensive (e.g. Collatz et al. 1998; Hall et al. 2000; Knapp & Smith 2001).

There was a decline - perhaps quite rapid - in atmospheric CO₂ concentration ca 30 m.y.a. in the Oligocene (Pagani et al. 2005; Zachos et al. 2008; Gerhart and Ward 2010; Arakaki et al. 2011) perhaps caused by the activities of ectomycorrhizal plants (Taylor et al. 2009; see above). Temperatures in the late Miocene were also decreasing (Arakaki et al. 2011). Taylor et al. (2010) and Ripley et al. (2010) compare the ecophysiology of C₃ and C₄ grasses, the latter sometimes being more sensitive to drought and recovering more slowly from it. C₄ grasses, grasslands and savanna may be favoured in environments with some combination of high temperatures and low CO₂ concentrations. When stomata close in plants with C₄ photosynthesis transpiration losses are reduced, so mitigating the effect of temperature and water stress, yet carbon fixation is not necessarily reduced and damaging photorespiration avoided, so mitigating the decrease in CO₂ concentration (Morgan et al. 2011; Sage et al. 2012). Interestingly, taxa like Miscanthus x giganteus carry out C₄ photosynthesis under decidedly cooler conditions than is common (Wang et al. 2008), while the C₃ Lolium perenne can also tolerate water stress (Holloway-Phillips & Brodribb 2010, see below). Declining CO₂ concentrations may also have made trees less competitive (Pagani et al. 2009). Many C₄ origins seem to be correlated with a reduction in annual rainfall, and grasslands transpire less than the woodlands they seem to have replaced (Retallack 2001). Increasing temperature, open habitats, and perhaps especially decreasing precipitation would all increase water stress, although by no means all C₄ grasses are drought tolerant (e.g. Edwards & Still 2007, esp. 2008; Edwards et al. 2007; Edwards 2009).

Some vegetation simulations show circum-Arctic grasslands early in the Tertiary (Shellito & Sloan 2006), although this is unlikely. Grassland grasses began diversifying in the Eocene (e.g. Bouchenak-Khelladi & Hodkinson 2011), and although some grasslands may have been developing in the Oligocene, widespread grasslands did not develop until far later. Thus evidence from palaeosols suggest that grasslands in the Great Plains may be late Oligocene in age (ca 24 m.y. old) although Argentinian grasslands may be older, Eocene in age (Retallack 1997b; Edwards et al. 2010). These palaeosols approach mollisols, a soil type known only from the Tertiary and uniquely associated with grasslands (Retallack 1997b). Short sod grassland with shallow soils may have appeared in the early Miocene in dry regions with 400 mm annual precipitation ca 20 m.y.a. (Retallack 2001). Tall sod grasslands made up mostly of C₄ grasses and with deeper soils appeared in the late Miocene ca 7-5 m.y.a. in areas with up to 750 mm annual precipitation, and it was these grasslands that had true mollisols. In their fullest development, mollisols are dark and deep (the carbon-rich layer may be 1 m or so); carbon is mixed with rounded clods of clay 2-3 mm across, and mollisols are nutrient-rich, with carbonate and easily-weathered minerals, and the soil is of course densely permeated by grass roots (Retallack 1997b).

C₄ grasses may have originated in the Oligocene ca 33 m.y.a., but they became diverse - and made a corresponding major contribution to overall vegetation biomass - only in the late Miocene 9-8 m.y.a., the process being complete as recently as the late Pliocene 3-2 m.y.a. (Bouchenak-Khelladi et al. 2009; Edwards et al. 2010; Strömberg & McInerney 2011; McInerney et al. 2011 for North America; Strömberg et al. 2011: South America; Arakaki et al. 2011; Sage et al. 2012). Similarly, the extensive Brazilian Cerrado, savanna vegetation with flammable C₄ grasses and plants, a number woody, that have become adapted to a fire regime, also developed within the last (10-)5 m.y. (Pennington et al. 2006b; Simon et al. 2009; Simon & Pennington 2012). C₄ photosynthesis is known from grasses from the Early to Middle Miocene in both the Great Plains and Africa, some 25-12.5 m.y.a. as it became energetically advantageous in some environments (e.g. Ehleringer 1997 and references; Christin et al. 2008a, 2011b). However, from the examination of phytolith assemblages, grass-dominated open habitats in Patagonia did not develop before ca 18.5 m.y.a., and it was open-habitat C₃ poöid grasses that were dominant then (Strömberg et al. 2011). Thus there is a pronounced lag at both global and local scales between the initial evolution and diversification of grasses that carry out C₄ photosynthesis and their ecological expansion (e.g. Strömberg & McInerney 2011) - a lag of over 20 m.y. Indeed, the Neogene has been called the age of grasses (c.f. Palaeos); however, of the some 11,300 species of grasses, only some 600 species dominate ecologically in grasslands and savanna, and most of these are C₄ photosynthesizers (Edwards et al. 2010).

The great expansion of C₄ grassland in particular may be due to the environmental changes discussed above and/or associated changes like accelerated fire cycles, etc. (Retallack 2001; Sage & Kubien 2003; Tipple & Pagani 2007; Vicentini et al. 2008). The high flammability of dry grasses, disturbance by grazers, and windiness are among the factors, many related, that would lead to the increased occurrence of fires and spread of grasslands (D'Antonio & Vitousek 1992 on exotic grasses; Retallack 2001; Woodward et al. 2004; Bond & Scott 2010). Scheiter et al. (2012) see an interaction between increased temperatures, favouring C₄ grasses, relatively low atmospheric CO₂, favouring the invasion of C₃ grassland by C₄ grasses, fire, allowing the expansion of grassland, and the development of savanna, with its shade intolerant and fire-resistant trees. Together this enabled the expansion of C₄ grassland and savannah in the late Miocene.

The amount and persistence of litter in grasslands is an important factor in their success. Grasslands accumulate litter very easily, and there is a negative correlation between silicon concentration - especially high in annual grasses - and rate of leaf decomposition (Cook & Leishman 2011b). The relatively low nitrogen content in grass litter also means that it decomposes slowly and accumulates (Wedin 1995; Pérez-Harguindeguy et al. 2000: Bromeliaceae could be similar!; Cornelissen et al. 2001). Leaves of poöid monocots (presumably including sedges) decompose more slowly than do those of other angiosperms (Cornwell et al. 2008). Thus grasses are particularly flammable because of the accumulation of their litter (Scheiter et al. 2012; Sage et al. 2012); certainly charcoal from fires has become abundant since the Late Miocene about 10 m.y.a. (Bond & Scott 2010). Fires would have encouraged the spreead of grasslands. Since grasses have their perennating parts underground, they are not harmed by fire, while burning suppresses woodland; nitrogen is also volatilized and lost. Both would favour grasses: The habitat was opened, and C₄ grasses in particular have a reduced requirement for photosynthetic enzymes and so a lower nitrogen requirement (Wedin 1995). (Although panicoid grasses recover well after fires, it is unclear if C₄ grasses perform better in this respect than C₃ grasses - Ripley et al. 2011.) The dense - and sometimes remarkably deep - root masses of grasses also make the establishment of woody vegetation in grassland difficult (D'Antonio & Vitousek 1992); the seedling/young plant stage is critical here (Bond & Midgley 2000). Bond et al. (2005) estimated that if there were no fires, about 52% of C₄ grassland and 41% of C₃ grassland would revert to forest; of the latter, over half would be dominated by gymnosperms. However, McInerney et al. (2011) suggest that the late Neogene expansion of C₄ grasses in North America, at least, was at the expense of C₃ grasses rather than of woody vegetation.

The total C sequestration in soil and above-ground biomass in grasslands is greater than that of the forests they replaced, and there is a shift in the sequestration pattern from above-ground parts to the soil (Retallack 2001). Indeed, estimates of the proportion of below-ground biomass in grasslands is as high as 80-95% (Dormaar 1992) accounting for 10-30% of global soil carbon storage (Hall et al. 2000); Gibson (2009) estimates ca 33% total C storage - 650-810 Gt. Grassland soils are notably moister than corresponding woodland soils, with increased weathering, yet somewhat paradoxically grasslands support a drier climate; woodlands have a higher albedo and transpire more (Retallack 2001). Overall, grasslands can be considered a long-term carbon and water sink, and one of the consequences of their activities is long-term global cooling (Retallack 2001).

To conclude. The relationships between C₃ and C₄ grasses, temperature, trees, moisture, atmospheric CO₂ concentration and fire are complex and dynamic. Grasslands and savanna currently cover about 40% of of the land surface of the globe, about half that area being within the tropics (Gibson 2009 for references). The global distribution of C₄ vegetation is ca 18.8 x 10⁶ km² (somewhat over 15% of the total) and that of C₃ vegetation, ca 87.4 x 10⁶ km² (Still et al. 2003). All told C₄ photosynthesis accounts for about 23-28% of terrestrial gross primary productivity, although the biomass of C₄ plants is only ca 5% of the global total (Still et al. 2003: 35.3 Pg C yr^-1, vs 114.7 Pg C yr^-1; Ito & Oikawa 2004; see also Lloyd & Farquhar 1994; Ehleringer et al. 1997; Retallack 2001). Another estimate suggests that grasslands in general - both C₃ and C₄ species are of course involved - currently account for 11-19% of net primary productivity on land (Hall et al. 2000). What makes grasslands still more distinctive ecologically is not just the abundance of grasses and their distinctive growth habit, but that relatively few species of grasses are ecologically dominant in any one place, and most of these seem to be C₄ grasses; the total is perhaps a mere 600 species (Edwards et al. 2010). Finally, C₄ grasses may have first appeared in the Oligocene ca 33 m.y.a., t they became diverse - and made a corresponding major contribution to overall vegetation biomass - only in the late Miocene 9-8 m.y.a., the process being complete as recently as the late Pliocene 3-2 m.y.a. (e.g. Bouchenak-Khelladi et al. 2009; Edwards et al. 2010; Strömberg & McInerney 2011; McInerney et al. 2011; Strömberg et al. 2011; Arakaki et al. 2011; Sage et al. 2012)

Grasses and Herbivory.

There are also suggestions that C₄ grasses and grazing are connected. Thus (Bouchenak-Khelladi & Hodkinson 2011) thought that there were (unspecified) "adaptive coevolutionary processes" going on between grass and grazer. C₄ plants tend to be less attractive to herbivorous animals because of their lower nitrogen concentration and greater amount of fibrous tissue (Caswell et al. 1973) and also because they have more sclerenchyma because their veins are closer (see Caswell et al. 1973 in part). Futhermore, the persistent dead leaves of most grasses may also decrease their palatability to grazers (Antonelli et al. 2010). The nitrogen content of C₃ and C₄ grasses does seem to be similar (Taylor et al. 2010). Be this as it may, there was a Miocene radiation of grazing mammals (Thomasson & Voorhies 1990; Retallack 2001; Keeley & Rundel 2003) that has been linked to the spread of prairie and savanna grasses (see also Cerling et al. 1997; Bouchenak-Khelladi et al. 2009, 2010a: considerable detail and many dates; Mihlbachler et al. 2011). These mammals evolved hypsodont dentition, i.e. teeth with high crowns, enamel extending below the gum lines, and short roots, apparently to deal with the wear caused by eating the abrasive grasses with their complex silica bodies.

However, tooth enamel seems to be harder than silica encountered in grasses (Sanson et al. 2007), although surprisingly little is known about the mechanics of tooth action (Sanson 2006). It is dust particles, likely to be more numerous in food eaten by a grazer than by a browser, that may be the most abrasive element in the food ingested (e.g. Kay and Covert 1983). But silica bodies do affect the feeding behaviour of at least some smaller herbivores, both mammals and insects, even if they are not the immediate "cause" of hypsodonty in mammalian teeth. Higher silica in grasses decreases the amount of nitrogen taken up by both armyworm (Spodoptera exempta) larvae and voles (Microtus), and in the latter in particular there are long-term negative effects on the growth of the caterpillar, perhaps via damage to the larval midgut. Indeed, the mandibles of armyworm larvae, made out of chitin, are worn down by silica, moreover, it is well known that grass tissues produced after attack by a herbivore (but not after comparable mechanical damage) have an increased silica concentration and are less attractive to the animals (see Massey & Hartley 2006, 2009; Massey et al. 2007b).

The relationship between silica and the mechanical protection of plant tissues is not straightforward. Although prairie grasses expanded in Nebraska in the Early Miocene ca 23 m.y.a., hypsodont ungulates were already around by then (Strömberg 2004, 2006; Mihlbacher et al. 2011). Massive diversification of ungulates is largely a Miocene phenomenon, Bovidae and Cervidae starting to diversify by at least 26 m.y.a. (Bouchenak-Khelladi et al. 2009), and herbivores that are now specialists on C₄ grasses seem to have evolved before those grasses came to dominate ecosystems (Edwards et al. 2010). Bouchenak-Khelladi et al. (2009) noted that the density of silica bodies in the leaf epidermis seems to have increased in a number of grass groups, perhaps as a defence against herbivory, however, Sanson and Heraud (2010) suggested that the silica there might not be in crystalline form and so be unable to cause wear on the enamel of mammalian teeth (and see above). Establishing connections between the evolution and rise to dominance of grasses in some ecosystems and the evolution of grazing animals and of hypsodonty needs more work; it is likely that the two are linked, but not at such a simplistic level as "high SiO₂ = hypsodonty" (see also Retallack 2001 for a summary); Bouchenak-Khelladi and Hodkinson (2011) noted that hypsodonty has been gradually increasing for 20 m.y., but there is no comparable documentation of the spread of grasslands.

Of course, silica is not the only defence that grasses have (Massey et al. 2007a), for instance, they vary in toughness, and may contain noxious metabolites, sometimes because of their association with endophytes (see above). In some grasses, at least, defence against herbivores is mediated by the production of volatiles which attract nematodes (to attack Diabrotica larvae) or parasitic wasps (to attack caterpillars) (Degenhardt 2009).

Other.

Understanding other aspects of the eco-physiology of Poaceae is important. 1. Woody bamboos, some 1,300 species, can grow to 30 m tall or more, and may live for 100 years before flowering; palms and bamboos are the two major woody monocot clades. Given that there is no secondary thickening in bamboos, how the vascular tissue of these plants remained functional was unclear. However, Cao et al. (2012 and references) found that in the bamboos they studied root pressure was sufficient to drive water the entire height of the plant; root pressure and plant height were strongly correlated. This would help in the repair of embolisms in the xylem.

2. In the poöid Lolium perenne, leaf hydraulic conductance may decrease during the day, with cavitation presumably occuring, yet photosynthetic rates may stay high, the stomata remaining open. The plant was able to recover from quite extreme hydraulic dysfunction, although here root pressure seemed not to be involved (Holloway-Phillips & Brodribb 2010). It will be interesting to see how widespead such behaviour is in the family.

3. The ecological success of Poaceae is not just because some adopted C₄ photosynthesis. Cooler temperate grasslands in the northern hemisphere are dominated by Poöideae, all of which are C₃ grasses. Thus although about 16% of all species growing in Quebec and Labrador north of 54^o N are Cyperaceae, Poaceae, all Poöideae, are next at 11% (Escudero et al. 2012). Understanding diversification in Poöideae entails understanding the evolution of cold tolerance and vernalization (Edwards 2009; Edwards & Smith 2010). Core Poöideae evolution may be linked with the cooling at the beginning of the Oligocene ca 33-27 m.y.a. (Strömberg 2005; Sandve et al. 2008; Sandve & Fjellheim 2010). Gene families implicated in low temperature stress response expanded prior to Poöideae diversification (Sandve & Fjellheim 2010), and proteins that inhibit ice recrystallization are known from the group (Sidebottom et al. 2000; Tremblay et al. 2005; Sandve et al. 2010). Poöideae have a complex relationship between day length, freezing tolerance and flowering (Dhillon et al. 2010). Furthermore, although only low levels of fructan - specifically levans - accumulation have been noted in many Poaceae, notably high levels are found only in Poöideae, although not in taxa of the "basal" pectinations like Nardus, Stipa and Phalaridinae (Smouter & Simpson 1989; Hendry 1993; Pollard & Cairns 1991). Fructans may enable Poöideae that accumulate them to survive drought or frost better, and they have been implicated in stabilizing cell membranes at low temperatures (Livingston et al. 2009; Sandve & Fjellheim 2010). Another factor contributing to the diversification of Poöideae may be the establishment of vernalization requirements (Preston & Kellogg 2008), although how widely this occurs outside the subfamily is unclear. Finally, the development of the Epichloë/Poöideae relationship may have been involved in the spread of Poöideae from shady to sunny open habitats in the predominantly cool-season climates that they favor (Kellogg 2001), the mutualism aiding the plant's defences against herbivores and drought (Schardl et al. 2008; Schardl 2010).

Other grasses also tolerate cooler condition, including the more northerly temperate bamboos (Bambusoideae: Arundinarieae) and the austral Danthonioideae. In the latter, evolution of cold tolerance is estimated to have begun ca 25 m.y.a. in the late Oligocene in Africa (Humphreys & Linder 2013). (see also Linder et al. 2013 to read).

4. The dumb-bell shaped stomata of grasses show remarkably rapid stomatal movements, very much faster than those few other stomata have been examined (Franks & Farquhar 2006). However, since the stomata of quite a number of other Poales are similar, it is unclear if they are a major component of the ability of grasses to spread as climates became drier at the end of the Eocene (Hetherington & Woodward 2003).

5. Much goes on in grass roots. Prominent rhizosheaths - mucilage from root cap cells, soil particles, bacteria, etc., all anchored to root hairs - occur in many Poaceae (McCulley 1995), especially those growing in drier conditions, although the distribution of such roots is poorly known. They are known from other Poales, but are apparently rare in broad-leaved angiosperms. Interestingly, C₄ grasses have roots with long root hairs yet may respond positively in terms of phosphorous uptake when forming endomycorrhizal associations - long root hairs and endomycorrhizal associations tend to be thought of as alternative ways of securing phosphorous supply, etc. (Schweiger et al. 1995 and references). Finally, Poaceae, apparently alone in flowering plants (Römheld 1987), acquire iron through chelation of ferric ions with non-protein amino acid siderophores which are then taken up by the roots; iron (and zinc) are commonly limiting trace elements in alkaline soils (Schmidt 2003; Kraemer et al. 2006). Interestingly, ectomycorrhizal plants, also noted for dominating the communities in which they occur, also produce siderophores. A number of grasses in different subfamilies accumulate glycine betaines and other compounds commonly associated with allowing plants to grow in saline conditions (Rhodes & Hanson 1993).

6. Some Poaceae have allelopathic reactions with other plants, Sorghum roots producing a quinone (an oxygen-substituted aromatic compound) and Festuca roots meta-tyrosine, a non-protein amino acid (Bertin et al. 2007). Benzoxazinoids, cyclic hydroxamic acids, are largely restricted to Poaceae, and are found in both Panicoideae and Poöideae; the genes involved in benzoxazionid synthesis are clustered on the chromosome. Benzoxazinoids confer resistance to fungi, insects, and even herbicides, and they, too, are allelopathic, but less so to other grasses in particular (Frey et al. 1997, 2009; Gierl & Frey 2001; Sicker et al. 2000: ecological role; Dick et al. 2012; Schullehner et al. 2008: non-grasses). Sindhu et al. (2008) note that the PACMAD clade is characterized by a gene that protects the plant against attack by the ascomycete Cochliobolus carbonorum.

7. Poaceae such as Spartina and Puccinellia can be major components of salt marshes. Salt tolerance in grasses is quite widespread, with 2/3 of the species being C₄ plants (Flowers & Colmer 2008). Some 200+ species are involved, and weak salt tolerance - tolerance of salinity up to ca 80mM NaCl - has evolved some 76 times (Bennett et al. 2013). Euhalophytes, tolerating at least 200mM NaCl, about half the salinity of sea water, have evolved some 43 times, and in both cases the clades involved are young and small; Bambuseae (sic) and Danthonioideae are notable for lacking even weak halophytes (Bennett et al. 2013).

At least some species of Micraira are resurrection plants (Sanchez-Ken et al. 2007).

Bacterial/Fungal Associations. Ascomycete clavicipitaceous endophytes are widely distributed among grasses (Clay 1990: review; Leuchtmann 1992: distribution and host specificity of grass endophytes; Schardl 2010; Rodriguez et al. 2009: endophytes in general); the association could be ca 40 m.y. old (Schardl et al. 2004). Some 30% or more of Poöideae are involved in these associations, and there is both horizontal and in particular vertical transmission of the fungus. The endophyte-grass relationship is usually described as being one of mutualism, although this may sometimes, at least, not be so (see Saikkonen et al. 1998; Gundel et al. 2006; Ren & Clay 2009), and the more that is found out about the relationship, the more complex it appears to be. One of the most important fungi involved is Epichloë (Clavicipitaceae), a systemic endophyte restricted to Poöideae; Neotyphodium is its asexual stage, perhaps representing hybrids of Epichloë species (Roberts et al. 2005; Moon et al. 2005; Rodgers et al. 2009: patterns of infection of the two forms). Hybridization of the fungus may even increase the competitive ability of the host grass under stressful conditions (Saari & Faeth 2012: greenhouse experiments). The larvae of Phorbia (or Botanophila) flies live on Epichloë stroma, and the adults transmit the fungal spermatia in a fashion analogous to insect pollination of flowers (Bultman 1995). Indeed, Epichloë synthesizes unique compounds that specifically attract the flies (Steinebrunner et al. 2008) and which may also be toxic to other fungi that secondarily invade the fungal stromata (Schiestl et al. 2006). However, the equilibrium of such relationships can easily be disturbed (Eaton et al. 2010). For details of the phylogeny and evolution of the endophyte association see Schardl (1996, 2002, 2010), Craven et al. (2001), Clay and Schardl (2002), Jackson (2004: possible codivergence), and Gentile et al. (2005).

Clavicipitaceae-Balansiae (Clay 1986; White et al. 2003: review) are now included in Hypocreales, the old Clavicipitaceae having been split up. Hypocreales include many insect pathogens, plant parasites, and especially parasites of other fungi, but also yeast-like obligate symbionts (of leaf hoppers). There has been widespread cross-kingdom host switching (e.g. Vega et al. 2009; Kepler et al 2012). Hypocreales may ancestrally have been plant parasites, although the immediate ancestor of grass endophytes may have been an insect pathogen (e.g. Spatafora et al. 2007; Vega et al. 2009). Some of these insect pathogens are also grass endophytes, and Metarhizium robertsii may even be both endophyte and insect pathogen (e.g. Sasan & Bidochka 2012).

These fungi synthesize a diversity of secondary metabolites (Spatafora et al. 2007), and the insect pathogens may also be antagonistic to plant pathogens (Vega et al. 2009 and references). Four groups of "grass" alkaloids are synthesized by Epichloë: Indole diterpenes, loliine (1-aminopyrrolizidines), peramine, and the ergot (ergolines) alkaloids (Fleetwood et al. 2007). Loliines are primarily active against insects (Schardl et al. 2007; Zhang et al. 2009).

The presence of endophytes affects both the palatability of grasses to herbivores and of their seeds to granivorous birds, the animals eating the infected material sometimes not thriving at all. The level of aphid infestation and that of their parasites and parasitoids is also affected (Omacini et al. 2001), as is the level of infestation of the plant by nematodes. Similarly, the endophyte also affects the palatability of the seeds to birds (Madej & Clay 1991), insect herbivory (Tanaka et al. 2005), the resistance of the plant to the effects of water stress (Hahn et al. 2007), and even the pattern and rate of decomposition of dead grass (Lemmons et al. 2005; see also Popay & Rowan 1994; Schardl 2010). Fungal endophytes may also affect root growth and root hair production (Sasan & Bidochka 2012).

Many other species of apparently symptomless endophytes (class 3 endophytes: Rodriguez et al. 2009) are also found in Poaceae, but little is known about their interactions with their hosts. Márquez et al. (2007) noted that only when the endophytic fungus (Curvularia) was infected with a virus was Dicanthelium lanuginosum, the host of the fungus, able to grow in volcanically-heated soils, suggesting the complexity of such relationships, while Marks and Clay (2007) discuss growth rate of endophyte-infected and -free plants under various conditions. Some root-associated endophytic fungi (class 4) are also coprophilic (Herrera et al. 2009), perhaps aiding in their dispersal. For fungal records - very numerous and diverse - on grasses, see Tang et al. (2007); there are at least 1933 species of fungi known from bamboos alone.

Bacteria, too, may be endophytic in grasses, and several bacterial endophytes are implicated in fixing one third to one fifth of the nitrogen needed by sugarcane in Brazil - the bacteria include Gluconacetobacter (alpha-Proteobacteria) and Herbaspirillum and Burkholderia (ß-Proteobacteria, for the latter, see also Fabaceae) (de Carvalho et al. 2011). A wide variety of bacteria have been isolated from the roots of Chrysopogon zizanioides (vetiveria) where they are implicated in the synthesis of terpenoids, etc., in the prized essential oils that the plant produces (del Guidice et al. 2008).

Parasitic rusts and smuts are common on Poaceae, and those on Bambusoideae and Poöideae are particularly distinctive (Savile 1979b); two thirds of Ustilaginales (smuts) - close to 600 species - are found on Poaceae (Kukkonen & Timonen 1979; Stoll et al. 2003). Some seventy species of Berberis are alternate hosts (the aecial stage) for Puccinia graminis, the black stem rust of wheat and other grain crops in Poöideae; this species (or complex) infects some 77 genera of mostly poöid grasses (Abbasi et al. 2005 and references). Cyclic hydroxamic acids are widely distributed in the family and confer resistance against a variety of fungal and insect pathogens (Frey et al. 1997).

Plant/Animal Interactions. Despite the silica bodies mentioned above, as well as the presence of alkaloids and other defences, caterpillars of nymphalid butterflies, in particular the browns, Satyrini, and related tribes like Morphini, Melantinini, etc., are common on Poaceae. Satyrinae as a whole diverged from other Nymphalidae some 80-85 m.y.a. (or perhaps at the K/T boundary: Heikkilä et al. 2011; see also Peña et al. 2011), but the main clades within it did not diverge until the later Palaeocene. Other Satyrinae eat commelinid monocots, sometimes also including grasses, but none of the other subtribes has more than 110 species, compared to the some 2,200 species of Satyrinae-Satyrini. Stem Satyrini may be about 65-55 m.y. old, and the crown group is later Eocene, some (47.8-)41.8, 36.6(-31.5) m.y. (Peña & Wahlberg 2008; Wahlberg et al. 2009; Peña et al. 2011: age depends on calibration points, position of Satyrini varies).

Satyrini larvae almost exclusively eat grasses, where they are the only common grazing insects. Their main diversification was some 36.6 m.y.a., perhaps contemporaneous with the initial spread of grasses (Peña et al. 2006, 2011; Peña & Wahlberg 2008). However, the move of satyrine butterflies from forests to more open environments where grasses are so abundant, not grass feeding per se, may have helped spur their diversification (Peña et al. 2011). Diversification has also occurred in Satyrini of more forested habitats, thus caterpillars of the largely South American subtribe Pronophilina, with well over 400 named species (?600 species total), are largely bamboo feeders that eat Chusquea. They are most diverse in the Andes just below the cloud forest-páramo transition at ca 3050-3250 m altitude, but some species are found in the páramo, where the bamboo Swallenochloa and some other bamboos grow (Pyrcz et al. 2009; Casner & Pyrcz 2010; Sklenár et al. 2011). Only a few Pronophilina species are found in comparable forests in east Brazil and Central America.

Galling dipterans, especially Cecidomyiidae, are quite common in grasses (Labandeira 2005). Cecidomyiid gall midges, notably Mayatiola (M. destructor is the Hessian fly), grow on Poöideae in North America (Gagné 1989). Shoot flies (Diptera-Chloropidae) form galls on monocots, especially grasses, but they are also simple herbivores and have other life styles (de Bruyn 2005). Chinch bugs (Hemiptera-Lygaeidae-Blissinae) have been most commonly observed on members of the PACMAD clade, less commonly on the BEP clade; the lygaeid Teracrini are also concentrated on Poaceae (Slater 1976). Poaceae provide food for both adults (as pollen) and larvae (as roots) of Chrysomelidae-Galerucinae-Luperini-Diabrotica beetles (Jolivet & Hawkeswood 1995).

Water often congregates in the hollow stems of bamboos, and a distinctive fauna lives there (Kitching 2000).

Pollination Biology & Seed Dispersal. Poaceae are predominantly wind-pollinated and usually have protandrous flowers with dangling anthers. However, some forest-dwelling grasses, especially smaller Bambusoideae, are pollinated by insects (Soderstrom & Calderón 1971). Streptochaeta may also be animal pollinated, since it lacks a plumose stigma and its anthers do not dangle; the flowers are protogynous (Sajo et al. 2008). Lodicules, modified members of the inner tepal whorl, help in the opening of the staminate or perfect flowers; they may be absent from carpellate flowers (see Sajo et al. 2007; Reinheimer & Kellogg 2009 for references). There is considerable variation in flower type in the family (e.g. see Le Roux & Kellogg 1999; Chuck 2010 for the development of unisexual flowers).

The caryopsis is often described as being the distinctive fruit type of Poaceae; it is a variant of an achene in which the testa and pericarp are fused. However, the fruit proper is rarely the dispersal unit (but c.f. the fleshy-fruited Alvimia - Bambusoideae), and there is quite a variety of diaspores and dispersal mechanisms in the family (e.g. Werker 1997). Dispersal is quite often by animals, attracted by structures like elaiosomes (Davidse 1987), while a variety of hooks and spikes attach the diaspores attach to passing animals (Centotheca is a good example). A number of taxa are wind-dispersed, for example, Andropogon has long hairs on the awns, while Spinifex and a few other genera are tumbleweeds. Awns can aid in both wind and animal dispersal, while the surface microstructure on awns, minute retrose bristles, may cause the achene to become "planted" in the ground (Elbaum et al. 2007; Humphreys et al. 2010b) or to move along the surface (Kulic et al. 2009; see also Davidse 1987). This is by a ratchet principle similar to that which operates when you put an entire inflorescence of Hordeum up your sleeve and you walk along; the inflorescence migrates up your arm and sometimes also down your back. Despite the apparent advantages of having an awn, this has been lost several times in Danthonioideae, at least, perhaps in association with the adoption of the annual habit where passive burial of seeds suffices (Humphreys et al. 2010b).

Woody bamboos are known for their tendency to dominate the vegetation and their synchronized flowering and fruiting, even when transported thousands of miles from their native habitat. Plants are monocarpic, and flowering may occur only every 120 years or so; after a rather protracted period of reproduction, the plant dies. This has profound effects both on the general vegetation and all organisms dependent on bamboos for food and shelter. The fruits are used as food by humans and they also attract animals - birds, rats, etc. - in very large numbers (Janzen 1976; Judziewicz et al. 1999). This behaviour is also found in some herbaceous bamboos and, depending on relationships within Bambusoideae, may even be plesiomorphic for the subfamily; it is an extreme form of masting (Curran & Leighton 2000 and references).

Vegetative Variation. Woody bamboos, for example Chusquea, may have a hundred or so branches at a node, borne in a fan-like arrangement. They are produced by a combination of multiple buds and axillary shoots with very short internodes, all nodes producing branches (see e.g. McClure 1973; Judziewicz et al. 1999; Tyrrell et al. 2012).

Genes & Genomes. Genome evolution in Poaceae has been particularly active. Comparisons of expressed sequence tags, etc., suggest that the genomes of Poaceae are much more different from the genome of Allium (Asparagales-Asparagaceae-Allioideae) than the genome of Allium is from that of Arabidopsis (Brassicaceae, Brassicales, rosid II: Kuhl et al. 2004).

As in other groups, genome duplication has played a major role in the evolution of the family. There has been a duplication of the whole genome in a clade that includes at least Zea, Oryza, Hordeum and Sorghum, i.e. the PACMAD/BEP clade, that has been dated to ca 70/70-66/70-50/73-56/50-40 m.y. (Goff et al. 2002; Paterson et al. 2004; X. Wang et al. 2005; Schlueter et al. 2004; International Brachypodium Initiative 2010). However, Vandepoele et al. (2003) think that this may be an aneuploidy event, rather than duplication of the whole genome. Soltis et al. (2009) suggested that diversification in Poaceae may be connected with this genome duplication, and the development of a cytosolic ADPglucose phosphorylase, perhaps unique to this clade, has been associated with it (Comparot-Moss & Denyer 2009), however, diversification of the groups including the cereals may have occurred ca 20 m.y. later (Paterson et al. 2004; c.f. International Brachypodium Initiative 2010). There has been very extensive duplication of genes - API, AG and SEP families - but not in genes of the AP3 lineage (Zahn et al. 2005a; see also Saski et al. 2007 for other duplications in the family). Malcomber and Kellogg (2005) suggest that there has been duplication of LOFSEP genes within Poaceae, while the duplication of AP1/FUL gene, apparently in stem-group Poaceae, may be involved in the evolution of the spikelet (Preston & Kellogg 2006). Developmental gene duplication and subsequent functional divergence seem to have played a very important role in allowing the development of the baroque diversity of inflorescences in the family (Malcomber et al. 2006; Zanis 2007; see also Doust & Kellogg 2002; Reinheimer & Vegetti 2008). For the evolution of the NADP-malate dehydrogenase gene following its duplication, see Rondeau et al. (2005).

There are over 500 species of temperate bamboos, and this whole clade is descended from an allotetraploid ancestor (Triplett et al. 2011). Z. Peng et al. (2013) suggest that genome dupication occured in the ancestor of the giant bamboo Phyllostachys heterocycla (P. edulis) 11.5-7.7 m.y.a., while a genome duplication/hybridization in the ancestor of Zea has been dated to ca 4.8. m.y. (Swigonová et al. 2004) - the two ancestors may have diverged ca 11.9 (Swigonová et al. 2004) or 20.5 m.y.a. (Gaut & Doebley 1997).

There are other important recent duplication events involving hybridization. The complex relationships within Danthonioideae may be connected with extensive past hybridizations (Pirie et al. 2008, 2009), as is notoriously the case in Triticeae (Jacob & Blattner 2006; G. Petersen et al. 2006a; Mason-Gamer 2008; Meimberg et al. 2009; Sun & Komatsuda 2010), subsequent polyploidy and introgression further complicating the picture. For a possible relationship between genus size, life form and polyploidy, see Hilu (2007).

Bennetzen (2007), Salse et al. (2008, 2009a, b) and Abrouk et al. (2010) discuss genome evolution in the family, suggesting that the base chromosome number (x) is 5, but in the [PACMAD + BEP] clade at least x increased to 12 after a genome duplication (to x = 10) and two interchromosomal translocations and fusions (to x = 12). n = 12 is still found in rice (Oryza), for example, while x = 10 in Panicoideae. However, Hilu (2004) suggested that the base chromosome number for the whole family might be x = 11. Certainly one or more rounds of genome duplication have occurred, with subsequent independent reductions in chromosome numbers (Schnable et al. 2009; Abrouk et al. 2010 and references). Within Poöideae there seems to have been independent reductions in chromosome number from n = 12 (International Brachypodium Initiative 2010). Winterfeld (2006) discussed cytogenetic evolution, mainly in Aveneae (= Poöeae.

Genome size varies considerably and at least in part independently of chromosome number, both increasing and decreasing (Caetano-Anollés 2005; Smarda et al. 2008; Schnable et al. 2009). There has been very substantial genome evolution in grasses, with that in Triticeae (Poöideae) being particularly accelerated (Luo et al. 2009; see also Messing & Bennetzen 2008; Salse et al. 2009a). Many Triticeae have massive genomes in part because of changes in base chromosome number (Jakob et al. 2004).

There has also been substantial evolution in the chloroplast genome (Leseberg & Duvall 2009; Guisinger et al. 2010 for literature), although details on where on the tree (and so when) particular changes occurred await more extensive sampling in Poales and "basal" Poaceae; the rate of plastid evolution may have since slowed down. These rate changes are placed at the level of Poaceae as a whole, although they might more correctly be put at the PACMAD/BEP node... Morris and Duvall (2010) discuss aspects of chloroplast genome evolutiom, focusing on Anomochloa. For a series of inversions in the single copy region and expansion of the inverted repeat at the single copy-inverted repeat boundary, see Hiratsuka et al. (1989) and Saski et al. (2007). For accD gene loss, see Katayama and Ogihara (1996), for deletions, etc., in the 3' end of the mat K gene, see Hilu & Alice (1999), for loss of introns in chloroplast genome, see Daniell et al. (2008) for references.

The mitochondrial coxII.i3 intron has developed a moveable element-like sequence (Albrizio et al. 1994), but there is a fair bit of variation in other monocots, too. Transposable elements, Mutator-like elements (MULEs), seem to have moved fairly recently by lateral transfer between rice, East Asian bamboos, and a number of Panicoideae-Andropogoneae (Diao et al. 2006), while Stowaway Miniature Inverted repeat Transposable Elements (MITEs) are common in the BEP clade, especially in Poöideae (Minaya et al. 2013). For the Hm1 resistance gene, see Sindhu et al. (2008), and for the complex evolution of the Rp1 disease resistance gene family, see Luo et al. (2010).

Economic Importance. Among the C₃ domesticates, several are Poöideae. Wheat (mostly Triticum aestivum - Poöideae), which provides one fifth of the calories eaten by humans, began to be domesticated ca 10,000 years ago; see Israel Journal of Plant Sciences 55(3-4). 2007, for an entry into the literature on domestication, also Fuller (2007), Baum et al. (2009: haploid genomes) and Carver (2009: general). Most domesticated forms are polyploid, and genome plasticity in connection with this polyploidy has been implicated of the success of the crop in cultivation (Dubcovsky & Dvorak 2007). For the domestication of barley (Hordeum vulgare), see Fuller (2007), Pourkheirrandish and Komatsuda (2007) and Azhaguvel and Komatsuda (2007). For a phylogeny of Oryzeae (Ehrhartoideae), see Guo and Ge (2005), and for information on the complex history of domestication of rice (Oryza spp.), which occurred in two places, at least, see Sweeney and McCouch (2007) and Fuller (2007).

Sorghum and Zea (Panicoideae) are among the important C₄ grain genera. The domestication of maize seems to have occurred in seasonal tropical forests in southwestern Mexico, perhaps the Balsas valley, some 8,700 years before present (Piperno et al. 2009; Ranere et al. 2009: summarized in Hastorf 2009); for a detailed summary of all aspects of maize biology, see Bennetzen and Hake (2009). For the domestication of pearl millet (Pennisetum glaucum), see Fuller (2007), and for that of sorghum (Sorghum spp.), see Dillon et al. (2007). Sang (2008) notes that single genes are involved in a number of major morphological transitions in the domestication of grains, such as the development of non-shattering rhachises; the genes may be quite different in unrelated species. For the domestication of sugarcane (Saccharum officinarum) in New Guinea, see Dillon et al. (2007) - note that Sorghum bicolor and Saccharum officinarum can be hybridized (e.g. Nair 1999). Glémin and Bataillon (2009) take a comparative viewpoint and look at how grasses in general have evolved under domestication.

Chemistry, Morphology, etc. Because of their great economic importance, many aspects of grass morphology, anatomy, cytology, etc., have been surveyed over the years. By no means all of these really useful early surveys are cited below, although most are easily traceable in the literature.

The primary cell wall hemicellulose and pectin polysaccharides of grasses are very different from those of other seed plants, both in overall composition and particularities of the composition of the xyloglucans (O'Neill & York 2003), and the polysaccharides are less branched than those elsewhere - but overall sampling is very poor. Hatfield et al. (2009) discuss acylation of lignin in grasses, and Boerjan et al. (2003) note that grasses in particular have a variety of minor lignin monomer units. There is evidence that ADP-glucose pyrophosphorylase, involved in starch synthesis, is very largely present in the cytosol, not in the plastids, in the endosperm of members of the PACMAD/BEP clade in grasses. It occurs in plastids in the starch-storing organs of other seed plants, probably even including the starchy endosperm of other commelinid monocots, but the sampling here, too, is poor (Beckles et al. 2001; Comparot-Moss & Denyer 2009).

Whether or not the division resulting in the trichoblast/atrichoblast pair in roots is asymmetric (Poöideae) or not, and, if it is symmetric, whether or not subsequent development of the two cells is the same, both vary (Kim & Dolan 2011). The sampling is poor, with no species from the basal pectinations and only one species each in Ehrhartoideae and Bambusoideae examined (Row & Reeder 1957: exceptions are no longer so; Kim & Dolan 2011). Poaceae have a nodal vascular plexus (Arber 1919), but I have no idea as to its general distribution and significance. Microhair variation in the family is extensive and of some use in delimiting major groups (Liphschitz & Waisel 1974; Amarasinghe & Watson 1988, 1990; Liu et al. 2010; Oli et al. 2012). Ligule variation is also extensive: Anomochlooideae are sometimes described as lacking a ligule (Judziewicz & Clark 2008, q.v. for other characters), or the ligule is described as being a ring of hairs. The leaf blades of Neurolepis (Bambusoideae) may be up to 4 m long.

Pharus has a number of features in common with Anomochlooideae, perhaps because they are both plants of the forest floor (Sajo et al. 2007, 2012). Its numerous distinctive features need to be integrated with the tree, but whether other members of the subfamily are similar is unknown, and Puelioideae are also very poorly known (see also Judziewicz & Clark 2008; Kellogg 2013).

The grass palea, which is often bicarinate, has often been interpreted as being prophyllar/bracteolar in nature, monocots commonly having bicarinate prophylls. However, in this scenario bracteoles would probably have had to be regained, since the immediate outgroups to Poaceae lack them. For suggestions, based on early studies of gene expression, that the palea and perhaps even lemma are calycine in nature and the lodicules are corolline, see Ambrose et al. (2000); A-type genes are expressed in both the palea and lemma (Whipple & Schmidt 2006). General comparative morphology might suggest that the lemma is a bract and the palea represents two connate tepals of the outer whorl; if the lemma is a perianth member, then loss of bracts is an apomorphy for all or most of Poaceae. The tepaloid nature of the lodicules is relatively uncontroversial (see Sajo et al. 2007; Reinheimer & Kellogg 2009; Yoshida 2012). For a summary of floral development in grasses, see Ciaffi et al. (2011); see also Rudall and Bateman (2004) and Ronse de Craene (2010).

Understanding the flowers of Streptochaeta and Anomochloa presents a challenge (see also Judziewicz & Soderstrom 1989). Flowers of Streptochaeta can be interpreted as having an outer perianth whorl of two (adaxial) members that ultimately become the single, bicarinate palea (there are sometimes three members in this outer whorl), and an inner perianth whorl of three members that ultimately become the lodicules. The three stamens common in grass flowers would then be those opposite the three members of the outer perianth whorl (see Whipple & Schmidt 2006; Preston et al. 2009; Reinheimer & Kellogg 2009 for further details). If Ecdeicoleaceae and Joinvilleaceae are sister taxa (Marchant & Briggs 2006) and given the likelihood that the flowers of Anomochloa are sui generis, the floral morphology of Streptochaeta may be plesiomorphic for the family, or aspects of it are apomorphies for the genus. Sajo et al. (2008) suggested that the flowers of Streptochaeta could be interpreted in more or less conventional terms, with a whorl of three rather coriaceous "bracts" being equivalent to lodicules and two adaxial "bracts" outside this perhaps representing the palea (although the structure interpreted as being a lemma was also adaxial...). Sajo et al. (2011, esp. 2012: floral structure assumed rather than demonstrated) described the flowers of Anomochloa as having glumes, palea and lemma (bracteoles, prophylls respctively), lodicules, etc.; there is basically a single carpel, although there seem to be vascular traces to three. The flowers of Ecdeicolea in particular are notably monosymmetric, with the two adaxial tepals of the outer whorl larger and keeled, and comparable differentiation in the outer perianth whorl occurs in Xyridaceae (q.v.); these are likely to be parallelisms.

It is difficult to interpret the arrangement of the pollen grains in the small anthers of Streptochaeta; they may be peripheral, at least initially (Kirpes et al. 1996; Sajo et al. 2009). Some grasses have pendulous, straight ovules. Although both crassi- and tenuinucellate ovules are reported for grasses, Rudall et al. (2005a) suggest that the reports of the former (e.g. Guignard 1882) need confirmation - parietal tissue is likely to be absent. When there are three carpels, the abaxial member is fertile (Kircher 1986). The caryopsis is often described as being a distinctive fruit type of the Poaceae; in a caryopsis, the seed coat and pericarp are fused, so it is basically a variant of an achene. Guérin (1899) suggests that the persistent part of the seed coat is tegmic, and he sometimes showed the exotegmen in particular as having quite large cells, or with quite thick walls, during development.

Poaceae are noted for their well developed, lateral embryo with a scutellum, coleoptile, coleorhiza, and mesocotyl (Tillich 2007). The structural equivalence of some of these parts is unclear. The scutellum is the distinctively-shaped haustorial part of the single cotyledon of other monocots (= the haustorial cotyledonary hyperphyll if one wants to be technical), while the coleoptile represents the sheathing base of the cotyledon, the scutellum and coleoptile originating on the same side of the embryo (Kaplan 1997: 1 ch. 5; Takacs et al. 2012). The mesocotyl could be an elongating nodal region or a structure that represents (part of) the hypocotylar region to which the cotyledonary stalk is adnate, while the coleorhiza may be part of the hypocotylar region. The "radicle" is endogeneous in origin, and possibly represents a lateral root, in which case Poaceae lack a radicle (and are homorrhizic...) (Kaplan 1997: 1 ch. 4, 5). Alpha prolamin genes, involved in the synthesis of seed storage proteins, evolved in Panicoideae-Andropogoneae 26-21 m.y.a. (Xu & Messing 2008).

See Kellogg (2013) for a comprehensive account of the family. Arber (1934) remains a classic treatment of the family, and Chase (1964) an introduction; see also the Grass Phylogeny Working Group (2001, 2011); McClure (1966) gives an account of bamboos, Bell and Bryan (2008) a good general treatment of grass morphology; for Micrairoideae, see Sánchez-Ken et al. (2007).

For the occurrence of ergot alkaloids, see Gröger and Floss (1998), for cell wall composition; see Fincher (2009), for non-starch soluble storage polysaccharides in the seed and fructans in vegetative parts, see MacLeod and McCorquodale (1958) and Meier and Reid (1982), for anatomy, see Metcalfe (1960), for C₄ photosynthesis, see also Kellogg (1999), for phytoliths and their distribution, see Piperno and Pearsall (1998), Piperno and Sues (2005) and Piperno (2006). For inflorescence morphology and development, see Vegetti and Anton (1996), Vegetti and Weberling (1996 and references: classical approach), Perreta et al. (2009) and Thompson and Hake (2009), for floral/spikelet evolution, see Yuan et al. (2009) and Thompson et al. (2009), for aerial branching, Malahy and Doust (2009), for the style of Triticum, see Li and You (1991), for embryo variation, see Reeder (1957), for proliferating antipodal cells, Anton and Cocucci (1984) and Wu et al. (2011), for endosperm and its development, see Olsen (2007) and Sabelli and Larkins (2009), and for the morphology of starch grains in the endosperm, see Shapter et al. (2008).

For general information on Bambusoideae, see Clark (1997), Judziewicz et al. (1999), and Judziewicz and Clark (2008), for foliar epidermis, see Yang et al. (2008a); for pollen in Chloridoideae, see Liu et al. (2004: not much variation).

Phylogeny. General. For overviews of the family phylogeny, see Kellogg (2000a, 2013) and the Grass Phylogeny Working Group (2001, 2011). Duvall et al. (2010) provide a preliminary tree based on whole chloroplast genomes. In a multi-gene study, Bouchenak-Khelladi et al. (2008) did not find strong evidence for the monophyly of Anomochlooideae, Streptochaeta possibly being sister to all other Poaceae; Micrairoideae might not be monophyletic, Isachne not having a fixed position; there was support for a sister relationship between Danthonioideae and Chloridoideae (see also Pirie et al. 2008); and Streptogyna may be sister to the whole PACCMAD clade - and it lacks the possible synapomorphies of that clade (Bouchenak-Khelladi et al. 2008; see also Bouchenak-Khelladi et al. 2009; Hisamoto et al. 2008). Relationships of the major clades within the PACCMAD (as it used to be called) and BEP clades were initially for the most part unclear. Thus the relationships of Poöideae (Hodkinson et al. 2007; Duvall et al. 2008a) and Ehrhartoideae (Cahoon et al. 2010, as Oryzoideae) are unclear in some analyses (see also Saarela & Graham 2010; c.f. Davis & Soreng 2008; Christin et al. 2008a: BEP clade paraphyletic and immediately basal to the PACCMAD clade). Relationships in the PACCMAD clade remained particularly difficult (Saarela & Graham 2010: sampling). However, the Grass Phylogeny Working Group II (2011) have found strong support for many of the relationships in the PACMAD (as it is now called) and BEP clades, although support for the first two branches in the PACMAD clade is still only weak. The position of Streptogyna remains unclear, but it may be close to Ehrhartoideae of the BEP clade.

Duvall et al. (2007) had found strong support for the BEP clade, albeit the taxon sampling was slight, while Ehrhartoideae and Poöideae had weak to moderate support as sister taxa (Bambusoideae not included: Saski et al. 2007: see also grass Phylogeny Working Group 2001). Hisamoto et al. (2008) found the relationships between the three subfamilies to be uncertain. Peng et al. (2010: 43 genes, only 10 taxa) found strong support for the relationships [E [B + P]] (ML and Bayesian analyses) and even stronger support for the relationships [B [E + P]] (neighbour joining), but the analyses of Wu and Ge (2011: 76 genes, 22 taxa; see also Bouchenak-Khelladi et al. 2008; Kelchner & the Bamboo Phylogeny Group 2013) supported the former set of relationships, and these are followed here.

Panicoideae. For discussions of the relationships - close and becoming ever more entwined - between Panicoideae and the old Centothecoideae, see Duvall et al. (2008a) and especially Sánchez-Ken and Clark (2008); the two are to be combined (Sánchez-Ken & Clark 2010; Teerawatananon et al. 2012). For relationships within Paniceae, see Zuloaga et al. (2000), Gómez-Martínez and Culham (2000) and Morrone et al. (2010, esp. 2012), for the bristle clade of Paniceae, see Doust et al. (2007), and those within Panicum itself, see Aliscioni et al. (2003) and Sede et al. (2008), within Pennisetum, in which Cenchrus is embedded, see Donadío et al. (2009) and Chemisquy et al. (2010), and within Setaria, see Kellogg et al. (2009); see also Sede et al. (2009a) for two new genera. Salariato et al. (2010) examined relationships within Melinidae, particularly fromn the point of view of inflorescence evolution. Ng'uni et al. (2010) looked at relationships with Sorghum, and López and Morrone adjusted the limits of Axonopus. For general information on Paniceae, see Crins (1991). For the phylogeny of Andropogoneae, see Kellogg (2000c) and Mathews et al. (2002), and for that of Paspalum, basically monophyletic, see Rua et al. (2010). Finally, for more information on relationships within Panicoideae, including those of some of its constituent genera, see papers in Aliso 23: 503-562. 2008.

Chloridoideae. Peterson et al. (2009, 2010a, 2011) suggest that relationships are something like [Centropodieae [[Triraphidae - Neyraudia (panicoid microhairs) + Triraphis] [Eragrostideae [Zoysieae + Cynodonteae (the bulk of the group)]]]]. Eragrostis and Sporobolus may be polyphyletic, while Muhlenbergia is paraphyletic, but there are a number of well supported (and with morphology, too) clades (Peterson et al. 2010b; Columbus et al. 2010); Leptochloa is polyphyletic (Peterson et al. 2012). For a morphological phylogenetic analysis of the subfamily, see Liu et al. (2005), for other relationships, see papers in Aliso 23: 565-614. 2008.

Danthonioideae. For a phylogeny of the Pentaschistis group, also character evolution there, see Galley & Linder (2007), for relationships in the subfamily as a whole, see Barker et al. (2007a), Pirie et al. (2008) and Cerros-Tlatilpa et al. (2011). Some relationships within Danthonioideae are reticulating (Pirie et al. 2008, 2009).

Ehrhartoideae. The relationships of Oryzeae have been much studied (Guo & Ge 2005; L. Tang et al. 2010 and references); for diversification within Oryza itself, see Zou et al. (2008).

Bambusoideae. Zhang and Clark (2000) restricted the limits of Bambusoideae accepted here; most of what is now the basal grade of Poaceae had been included in bamboos at one time or another. Clark and Triplett (2006) discussed relationships within the subfamily, previously divided into the woody Bambuseae and the herbaceous Olyreae. The woody temperate bamboo group may be sister to the rest of the subfamily; the monotypic Buergersiochloa, from New Guinea, is sister to the rest of the herbaceous Olyreae (e.g. Kellogg & Watson 1993; W. Zhang & Clark 2000; Bouchenak-Khelladi 2008). Sungkaew et al. (2009; five plastid genes; Kelchner & the Bamboo Phylogeny Group 2013) retrieved the relationships [Arundinarieae [Olyreae [Neotropical (strictly) Bambuseae + Paleotropical & Austral Bambuseae]]] and map the distributions of each of these groups. However, Kelchner and the Bamboo Phylogeny Group (2013) noted that the position of Olyreae in particular was not secure, and it might be sister to the rest of the subfamily. For a phylogeny of the woody bamboos, see Clark et al. (2008: resolution poor), of neotropical woody bamboos, see Clark et al. (2008) and Fisher et al. (2009), of palaeotropical woody bamboos, see Yang et al. (2008b: resolution o.k., baccate fruit arose in parallel), of Bambusa and its relatives, see Yang et al. (2010) and Goh et al. (2010), of Dendrocalamus, see Sungkaew et al. (2010), of temperate bamboos, see Peng et al. (2008), and of Bambuseae-Arthrostylidiinae, see Tyrrell et al. (2009, 2012). Burke et al. (2012) looked at relationships and timings based on analysis of plastid genomes. Disentangling relationships in Arundinarieae is proving difficult. Zeng et al. (2010) found rather little resolution despite sequencing ca 9,000 base pairs. The extent of the problem has been confirmed: The Phyllostachys clade that was recovered in in plastid analyses was pulverised into 24 bits in nuclear gene analyses; hybridization is involved (Y.-X. Zhang et al. 2012). For hybridization in the ancestor of temperate bamboos, see Triplett et al. (2011), and for hybridization in paleotropical bamboos, see Goh et al. (2013).

Poöideae. There are several papers on Poöideae in Aliso 23: 335-471. 2008; see also Soreng and Davis (2000) and Schneider et al. (2009) for relationships within the whole subfamily. For the ndhF gene, structural features of chloroplast and nuclear genomes, etc., and the phylogeny of Poöideae, see Davis and Soreng (2008). It is not certain the the duplication of the ß-amylase gene is an apomorphy here; one of the gene copies breaks down starch into fermentable sugars in the endosperm, while the other is more broadly expressed in the plant, as it is in other Poaceae (Mason-Gamer 2005). For relationships and morphology in Phaenospermateae (inc. Duthieae), see Schneider et al. (2011); Phaenosperma itself is a very distinct plant previously included in Bambusoideae. For a phylogeny of Poeae, which should now include Aveneae, see Grebenstein et al. (1998), Quintinar et al. (2007, also Döring et al. 2007; Soreng et al. 2007; Saarela et al. 2010, 2011; Gillespie & Soreng 2011), for that of Poa, see Gillespie and Soreng (2005), Gillespie et al. (2009) and Soreng et al. (2010, 2011). See also Gillespie et al. (2008, 2010) for relationships in Poinae, Quintanar et al. (2010) for those in Koeleriinae, Essi et al. (2008) for relationships around Briza, and Consaul et al. (2010) for polyploid speciation in Puccinellia. For a phylogeny of Stipeae, see Romaschenko et al. (2007, esp. 2008, 2009, 2010, 2011, 2012; Jacobs et al. 2008; Barkworth et al. 2008): Macrochloa may be sister to the rest of the tribe and there are parallel diversifications in the Old and New Worlds; characters traditonally thought to be phylogenetically important appear not to be so. For New World Stipeae, see Ciadella et al. (2010: sampling). Inda et al. (2008a) discuss the biogeography of Loliinae, which seems to have involved multiple dispersal events from a centre in the Mediterranean region over the last ca 13 m.y. A number of taxa show complex reticulating patterns of relationships; for those in Triticeae in particular, see G. Petersen et al. (2006a), Mason-Gamer (2008), and Sun and Komatsuda (2010) and references.

Classification. For the basic classification of the family, see the Grass Phylogeny Working Group (2001: a few small taxa remain unplaced in subfamilies, 2011); there are further changes in detail, but the main outline now seems clear. Watson and Dallwitz (1992b onwards) includes generic treatments, etc., but a more current treatment is to be found in Kellogg (2013). However, given all the ongoing work in the family web-based lists are much to be desired; Grassworld, which has just started up, may be preferred over GrassBase and the lists dependent on it like the World Checklist of Monocots. The need is to stay current with all the changes that are being proposed; Vorontsove and Simon (2012) estimated that 10-20% of the species names would change by the time phylogenetic rearrangements in the family are complete. The temptation is to chip off small monophyletic taxa from a paraphyletic residue; synthesis may be needed.

Peterson et al. (2010) provide a detailed suprageneric classification of Chloridoideae (see also Columbus et al. 2010 for Muhlenbergia; Peterson et al. 2012 for Leptochloa and relatives). Sánchez-Ken and Clark (2010) outline a tribal classification for Panicoideae s.l. (including Centothecoideae), while Morrone et al. (2012) provide a comprehensive classification of Paniceae and their immediate relatives. Setaria will have to be dismembered (Kellogg et al. 2009). Panicum itself is getting pulverized, perhaps overly much so (e.g. Sede et al. 2008, 2009b; Zuloaga et al. 2010); Panicum s.l. has about 500 species, s. str. ca 100 species, while Dicanthelium has about 55 species (Zuloaga et al. 2007). Cenchrus is to include Pennisetum (Chemisquy et al. 2010). Linder et al. (2010) offer a subfamilial classification of Danthonioideae; generic limits are difficult there and there has been some confusing hybridization (Pirie et al. 2009; Humphreys et al. 2010a).

Generic limits in Bambusoideae are proving especially problematic. For generic delimitation in the temperate bamboos, see Peng et al. (2008); the whole clade is descended from an allotetraploid ancestor, and, complicating the issue, there has been hybridization since (Triplett & Clark 2010; Triplett et al. 2011). There are also generic problems in Bambusoideae-Arundinarieae (Zeng et al. 2010) and -Bambuseae-Arthrostylidiinae (Tyrrell et al. 2009, 2012); Chusquea must include Neurolepis (Fisher et al. 2009). For a tribal and subtribal classification of Bambusoideae, see the Bamboo Phylogeny Group (2012).

Schneider et al. (2009) outlined tribal limits within Poöideae. For generic limits around Piptatherum, see Romaschenko et al. (2011). For a catalogue of New World Poöideae, see Soreng et al. (2003). Hybridisation, introgression, and polyploidy are rife in Poöideae-Triticeae (e.g. G. Petersen et al. 2006a; Mason-Gamer 2008), which include a number of important grain genera such as Triticum, Hordeum, etc. Genera are certainly not monophyletic here, but are based on different genome combinations that are (hopefully) correlated with morphological variation (Dewey 1984; Löve 1984); Barkworth (2000) summmarises the history of the classification of this group (see also Goncharov 2011 for taxonomic confusion in Triticum).

Apparently the earliest name for Chloridoideae was Chondrosoideae Link (Thorne & Reveal 2007), a sort of resurrection name - Googling it (as of 3.vii.2007) returned only Thorne and Reveal themselves, apparently the only people to have used it for some time, and about 42,100 returns for Chloridoideae. However, the name Chloridoideae has since been used by Reveal himself (2012).

Botanical Trivia. A typical sheep consumes more than 10kg of silica phytoliths per year (Baker et al. 1959), yet this may affect its teeth very little (Sanson et al. 2007).

Thanks. I am very grateful to E. A. Kellogg for discussions about the evolution of this family.