EXTANT SEED PLANTS

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 rich in guaiacyl units; true roots present, apex multicellular, xylem exarch, branching endogenous; arbuscular mycorrhizae +; shoot apical meristem multicellular, interface specific plasmodesmatal network; stem with ectophloic eustele, endodermis 0, xylem endarch, branching exogenous; vascular tissue in t.s. discontinuous by interfascicular regions; vascular cambium + [xylem ("wood") differentiating internally, phloem externally]; wood homoxylous, tracheids +; tracheid/tracheid pits circular, bordered; sieve tube/cell plastids with starch grains; phloem fibers +; stem cork cambium superficial, root cork cambium deep seated; nodes ?; stomata ?; leaf vascular bundles collateral; leaves megaphyllous [determinancy evolved first, then ad/abaxial symmetry], spiral, simple, axillary buds +[?], prophylls [including bracteoles] two, lateral, veins -5 mm/mm² [mean for all non-angiosperms 1.8]; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores, i.e. no distal pore for release of gametes] +, grains mono[ana]sulcate, exine and intine homogeneous; ovules unitegmic, crassinucellate, 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, with cell walls, with many flagellae; female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large", first cell wall of zygote transverse, embryo straight, endoscopic [suspensor +], short-minute, with morphological dormancy, white, cotyledons 2; plastid transmission maternal; two copies of LEAFY gene, PHY gene duplication [N/O//A/C and P//BE lines], mitochondrial nad1 intron 2 and coxIIi3 intron present.

MAGNOLIOPHYTA

Plant woody, evergreen; lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], lignins derived from both coniferyl and sinapyl alcohols, containing syringaldehyde [in positive Maüle reaction, syringyl:guaiacyl ratio less 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; stem with 2-layered tunica-corpus construction; wood fibers and wood parenchyma +; reaction wood ?, with gelatinous fibres; starch grains simple; primary cell wall mostly with pectic polysaccharides; tracheids +; sieve tubes eunucleate, with a sieve plate and cytoplasm with P-proteins, companion cells from same mother cell that gave rise to the sieve tube; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, veins (1.7-)4.1(-5.7) mm/mm², endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, development in general centripetal, numbers unstable; P not sharply differentiated, outer members not enclosing the rest of the bud, smaller than inner members; A many, with a single trace, introrse, filaments stout, anther ± embedded in the filament, tetrasporangiate, dithecal, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally by action of hypodermal endothecium, endothecial cells elongated at right angles to long axis of anther; tapetum glandular, binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, binucleate at dispersal, trinucleate eventually, tectum continuous or microperforate, ektexine columellar, endexine thin, compact, lamellate only in the apertural regions; nectary 0; G free, several, ascidiate, with postgenital occlusion by secretion, few [?1] ovules/carpel, ovules marginal, anatropous, bitegmic, [outer integument often largely subdermal in origin, inner integument dermal], micropyle endostomal, integuments 2-3 cells thick, nucellus at apex of ovule 1-3 cells thick, megasporocyte single, megaspore lacking sporopollenin and cuticle, chalazal, female gametophyte four-celled [one-modular, nucleus of egg cell sister to one of the polar nuclei], stylulus short, hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, dry [not secretory]; P deciduous in fruit; seed exotestal; pollen germinating in less than 3 hours, siphonogamy, tube elongated, growing at 80-600 µm/hour, with callose plugs and callose-based walls, penetrating between cells, penetration of ovules within ca 18 hours, distance to first ovule 1.1.-2.1 mm; tube moves between nucellar cells, double fertilisation +, endosperm diploid, cellular [first division oblique, micropylar end initially with a single large cell, chalazal end more actively dividing], copious, oily and/or proteinaceous, embryo cellular ab initio, minute; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, 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 PHYA + C/PHYB + E gene pairs.

Evolution. Possible apomorphies for flowering plants are in bold. Note that the actual level to which many of these features, particularly the more cryptic ones, should be assigned is unclear, because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied, there is considerable variation between families in particular for several of these characters, and also because details of relationships among gymnosperms will affect the level at which some of these characters are pegged. For example, if reticulate-perforate pollen is optimized to the next node on the tree (see Friis et al. 2009 for a discussion), it effectively makes the pollen morphology of the common ancestor of all angiosperms ambiguous... For other features such a a nucellus only one (Nymphaeales) to three cells thick above the embryo sac and a stylar canal lacking an epidermal layer, although plesiomorphous for basal grade angiosperms (Williams 2009), where on the tree a thicker nucellus and a stylar epidermal layer are acquired has not yet been indicated.

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

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 paracytic or tetracytic, neighbouring cells with parallel cell divisions; endosperm starchy.   Back to Main Tree

Evolution. The stem group for this clade dates to about 120 million years before present, while Poales diverged from [Commelinales + Zingiberales] ca 117 million years before present (from Janssen & Bremer 2004); Magallón and Castillo (2009, which consult for more details) suggest ca 123 million years for relaxed and 111 million years for constrained penalized likelihood stem group datings of Poales, the stem group of the whole clade being 128 to 115 million years old (relaxed and constrained estimates again).

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.

POALES Small  Main Tree, Synapomorphies.

Mycorrhizae absent; vessels also in stem and leaf; SiO₂ epidermal; raphides 0; P = K + C, micropyle bistomal, style well developed, stigmas small, stigma dry; endosperm nuclear, embryo size?; cotyledon hyperphyllar, haustorial [?level]; mitochondrial sdh3 gene lost. - 17 families, 997 genera, 18325 species.

Evolution. Divergence within the Poales clade begins ca 113 million years before present (Janssen & Bremer 2004) or 109-106 million years before present (Leebens-Mack et al. 2005), while Wikström et al. (2001) suggest an age for the clade of 87-83 million years before present, divergence beginning 72-69 million years before present. Magallón and Castillo (2009, which consult for more details) suggest ca 109-108 million years for relaxed and 99 million years for constrained penalized likelihood crown group datings - probably underestimates.

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 (2008) found a similar pattern.

Chemistry, Morphology, etc. There is interesting variation in the way pollen is arranged in the pollen loculi; the plesiomorphous condition is likely to be central, i.e., some grains are not in contact with the tapetum, but in some taxa it is peripheral, all grains being in contact with the tapetum (Kirpes et al. 1996). General information is taken from Linder and Rudall (1993) and (2005: detailed discussion of morphological evolution and diversification in Poales); 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 for seedling morphology and evolution, see Tillich (2007).

Phylogeny. 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 alone have septal nectaries, along with Rapateaceae, in Poales. Bromeliaceae and Typhaceae are often basal branches with respect to other clades in Poales (Givnish et al. 2005, 2008 [but rooting]; also Graham et al. 2006). Nevertheless, Rapateaceae appear to be sister to all other 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; cf. Givnish et al. 2006b). Similarly, Typhaceae are placed sister to Bromeliaceae with weak jacknife support but strong Bayesian posterior probabilities (Bremer 2002). Recent work 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; see also Rudall & Linder 2005; Givnish et al. 2005, 2007, but rooting; Graham et al. 2006 for this latter position).

Within Poales there are some well-supported groups, the Xyridaceae, Juncaceae and Poaceae and their respective relatives, although the exact composition of the first clade remains somewhat unclear. There is support for these three groups forming a larger clade (Givnish et al. 2005; 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). 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. 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. The order itself does not have very strong support. 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.

Within the remaining Poales there are two main clades.

1. Cyperaceae and Eriocaulaceae and their relatives may form one clade. Xyridales of Kubitzki (1998c) had included Mayacaceae, Xyridaceae, Eriocaulaceae and Rapateaceae. There was some evidence for a group with 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 are 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 link 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 remained unclear.

The situation seems, however, to be becoming tidier. Saarela et al. (2006, esp. 2007) have recently shown 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 at the base of the clade [Thurniaceae [Juncaceae + Cyperaceae]]: Mayacaceae are sister to the other members, then [Xyridaceae + Eriocaulaceae] are sister to Cyperaceae and their relatives (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).

2. Poaceae and their immediate relatives form the other clade. (Note that in versions 7 [before November] and earlier of this site, Eriocaulaceae and their relatives were weakly linked to Poaceae et al.). For a molecular study, see Bremer (2002), and for a useful detailed morphological and molecular analysis combined, see Michelangeli et al. (2003), also Hahn et al. (1995: details on deletions in the ORF 2280 region).

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 Dumortier, Centrolepidales Takhtajan, Cyperales Hutchinson, Eriocaulales Nakai, Flagellariales (Meisner) Reveal & Doweld, Hydatellales Reveal & Doweld, Juncales Dumortier, Mayacales Nakai, Rapateales (Meisner) Reveal & Doweld, Restionales J. D. Hooker, Typhales Dumortier, Xyridales Lindley - Bromelianae Reveal, Hydatellanae Reveal, Juncanae Takhtajan, Poanae Reveal & Doweld, Rapateanae Doweld, Typhanae Reveal - Bromeliidae C. Y. Wu, Juncidae Doweld - Bromeliopsida Brongniart, Juncopsida Bartling

Typhaceae + Bromeliaceae: three-nucleotide deletion in the atpA gene.

TYPHACEAE Jussieu, nom. cons.   Back to Poales

Plant rhizomatous; flavonoids +; SiO₂ bodies 0; starch grains pteridophyte-type, amylophilic; leaves two-ranked; plant monoecious; inflorescences complex; flowers very small; P chaffy; A 1-8, tapetum plasmodial, 8 nuclei/cell, pollen trinucleate, monoulcerate, nectary 0; G pseudomonomerous, 1 pendulous apotropous ovule/carpel, style + [?], branches long, stigma rather elongated, on one side; endosperm helobial, cell wall formation in small chalazal chamber before that in large micropylar chamber, 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.

Sheath not distinct; inflorescence as globose heads; P 1-6, when 3, median member adaxial; staminate flowers: anthers extrorse-latrorse; carpellate flowers: antipodal cells multiply after fertilisation, stigma papillate; fruit a spongy drupe, with micropylar plug; P persistent; testa membranaceous; 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.

Cuticular waxes as aggregated rodlets; sheath distinct; inflorescence densely spicate; P 0, staminate flowers: A connate, tapetal cells ?8-nucleate; carpellate flowers: long hairs on pedicels; 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 - note that 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. Typhaceae are ca. 109 million years old, the two genera included separating ca 89 million years before present (Janssen & Bremer 2004).

Similar rusts are shared by the two genera (Savile 1979).

Chemistry, Morphology, etc. Much information is taken from Kubitzki (1998d: general); see also D. Müller-Doblies (1970: inflorescence and flower) and Grayum (1992: pollen). The two genera are palynologically almost identical.

For general information on Typha, see Thieret and Luken (1996: southeast U.S.A.). Some flowers of Sparganium may have a second, empty loculus, or there may even be three fertile loculi (Dahlgren et al. 1985). On the other hand, fossil Sparganium may have up to 7-locular fruits (Cook & Nicholls 1986)! See U. Müller-Doblies (1970) for flower and embryology.

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

BROMELIACEAE Jussieu, nom. cons.   Back to Poales

Rosette plants, usu. herbs; (C-glycosylated/6-oxygenated) flavones, flavonols +; vessel elements with scalariform perforation plates; mucilage +; cuticular waxes as aggregated rodlets; stomata with oblique cell divisions; water storage tissue in mesophyll, fibrous bundle sheaths +; indumentum lepidote; leaves spiral, curved, thick, horny, base dilated, no distinct sheath; inflorescence bracts often colored; (A basally connate; adnate to C), septal nectaries +, 2-many ovules/carpel, one cell layer of nucellus at micropyle, epidermal cells elongated, micropyle ?, style + long, apically ± trifid, conduplicate-spiral, stigmas also wet; fruit a septicidal capsule, K persistent; seeds testal-tegmic; endosperm helobial, cell wall formation in small chalazal chamber precedes that in large micropylar chamber, embryo (long), cylindrical, often lateral; hypocotyl and hypophyll common; x = 25, chromosomes 2.75³ µm long.

57[list]/1700 - eight groups below. (Sub)tropical America; W. tropical Africa (map: from Givnish 2004a). [Photos - Flower.]

1. Brocchinioideae Givnish

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

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

Rest: cap cells of trichomes dead; septal nectaries below the ovular zone.

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.

Rest: (C often with subbasal scales and/or longitudinal callosities).

3. Tillandsioideae Burnett

Epiphytes, air bromeliads (also tank forming), roots often for attachment only (0); scales radially symmetrical; leaf margin entire; (flowers in inflorescence two-ranked); ovules with chalazal appendage, (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; (n = 17, 21), karyotype bimodal; primary root none or soon aborting.

9/1015: Tillandsia (540: polyphyletic), Vriesia (195: poly/paraphyletic), Guzmania (170), Werauhia (70), Racinaea (60). Almost the range of the family in America.[Photo - Flower]

The hairs in Tillandsioideae develop in a variety of ways (Palací et al. 2004; Barfuss et al. 2005) and variation in stigma morphology is also great (Brown & Gilmartin 1989).

For phylogenetic relationships, see Barfuss et al. (2004, 2005, the latter with a tribal classification and extensive discussion on morphology); generic limits need attention!

Synonymy: Tillandsiaceae Wilbread

Rest: ?

4. Hechtioideae Givnish

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

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

Rest: ?

5. Navioideae Harms

Xeromorphic; water storage tissue peripheral; stellate chlorenchyma 0; leaf margin serrate/entire; C minute; seeds winged or not.

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

6. Pitcairnioideae Harms

Scales ± divided; leaf margin?; (flowers monosymmetric), G to inferior, ovules with chalazal appendage, (outer integument ca 5 cells across; several cells layers of nucellus at micropyle); 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).

6/515: Pitcairnia (280), Dyckia (125), Pepinia (68), Forsterella (30). Mexico to Chile, Pitcairnia feliciana W. Africa.

Puyoideae + Bromelioideae: ?

7. Puyoideae Givnish

Rather xeromorphic [hypodermal sclerenchyma +, internal water storage tissue, chlorenchyma undifferentiated; trichomes in parallel rows, foliar trichomes with well developed wings]; leaf margin serrate; flowers monosymmetric, K contorted, C clawed, tightly spiralled after anthesis, several cells layers of nucellus at micropyle [?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 bromeliads, roots often for attachment only; scales irregular peltate; leaf margin entire/serrate; (perianth tube/hypanthium +), (K asymmetrical; pollen porate), (C with adaxial subbasal petal appendages), G inferior, ovules with chalazal [= funicular] appendage, (micropyle bistomal), 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. [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. Stem-group Bromeliaceae are dated to ca 112 million years before present, divergence within the crown group to ca 96 million years before present (Janssen & Bremer 2004: Brocchinia not included). However, Givnish et al. (2004a, 2008a) suggest comparable ages of 84 and 23 million years before present respectively, with radiation from an ancestral home on the Guayana Shield (see also Givnish et al. 1997); divergence with Brocchinia may have begum some 14 million years ago. Wikström et al. (2001) suggests a stem group age of 72-69 million years before present... Pitcairnia feliciana seems to have moved to Africa by long distance dispersal (Givnish et al. 2008a).

Riodininae-Riodininae larvae may be found on Bromeliaceae (and Orchidaceae: Hall 2003 and references).

Bird pollination is common in Bromeliaceae (Stile 1981 and references; Givnish et al. 2008).

Some two thirds of Bromeliaceae have CAM metabolism, although details of the evolution of this feature remain unclear (Crayn et al. 2000, 2004; Reinert et al. 2003; Schulte et al. 2005); it has evolved more than once in the family. 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). 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).

The diversity of growth forms in Bromeliaceae is well known. Many taxa are terrestrial, and have a well-developed root system. Epiphytes are common. About 1,700 species - and so just over half the family - are epiphytic (Luther & Norton 2008: epilithic species not included). Tillandsioideae have rather elegant multicellular peltate trichomes that take in water, and here the roots may be for attachment only. Thus adult plants of Tillandsia usneoides (Spanish moss) entirely lack roots, the plants growing happily on any available support, including telegraph wires (hairs in Tillandsia may also reflect light and so provide photoprotection: Pierce 2008). A few Tillandsioideae also have tanks formed by the closely appressed overlapping bases of the leaves; the apical meristem is submerged and at the bottom of the tank, and these are especially well developed in Bromelioideae. In this latter subfamily there is a major clade that has tanks (taxa with tanks also often have asymmetric sepals and porate pollen - Schulte & Zizka 2008; Schulte et al. 2009). 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. Phosphate is taken up very efficiently by the hairs on the leaves in tank epiphytes like Aechmea fasciculata and either moved elsewhere in the plant or stored as phytin, the salt of a cyclic compound to which H₂PO₃ moieties are attached (Winkler & Zotz 2009; Gonsiska & Givnish 2009). Perhaps somewhat paradoxically, adaxial leaf surfaces in Bromelioideae are hydrophilic while abaxial surfaces are hydrophobic (Reuter & Brown 2009). A diverse fauna showing considerable endemism is associated with the tanks: animals include many insects, even specialised diving beetles (Dystiscidae) whose evolution may be almost contemporaneous with the appearance of the tank habitat (Balke et al. 2008), land crabs, earthworms, ostracod crustaceans, protists and the like (Thienemann 1934; Kitching 2000, general; Greeney 2001, bibliography). In Trinidad, at least, mosquitoes that breed in the tanks help spread malaria (Pittendrigh 1948). Brocchinia is only a small genus, but it has a great variety of ways in which nitrogen is taken up, different growth forms, and it includes ant plants; Givnish et al. (1997) discuss the diversification of the genus, which is clearly rather old since it is sister to the rest of the family. For possible carnivory in Brocchinia reducta, see Givnish et al. (1984); the tillandsioid Catopsis berteroniana traps terrestrial arthropods but also harbours larvae of the mosquito Wyeomyia (Frank & O'Meara 1984; Gonsiska & Givnish 2009).

The rate of molecular evolution in Bromeliaceae is very low, ca 0.00059 substitutions/site/million years; although the family is not particularly woody, its members have a long generation time, which seems to be connected with a 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); however, the former position is incorrect (W. Till, pers. comm.). Tapetum development is described as being intermediate, the cells being initially secretory, but tending to invade later (Sajo et al. 2005). 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 taxa with these "superior" ovaries (they are fused when the ovary is inferior). Variation in ovule morphology is extreme (e.g. Gross 1988a).

For information on stigma morphology, see Brown and Gilmartin (1988, 1989), for nectaries, Böhme (1988) and Sajo et al. (2004b), for seed anatomy, Gross (1988a) and Varadarajan and Gilmartin (1988a), for petal appendages, Brown and Terry (1992), for the ovule, Sajo et al. (2004a), for germination, Gross (1988b), for chromsomal evolution, see Gitaí et al. (2005), for phytoliths, see Piperno (2006), for cultivated bromeliads, Rauh (1990), etc., for rhizome and root anatomy, see Proença and Sajo (2008), 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 their Fig. 1, also 2009), which are rather similar to those of 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. Hechtia (P: 55 - circumferential winging, as with Navia), were of uncertain position, not linking with either major group (Tillandsioideae, Bromelioideae + Pitcairnioideae) 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). The subfamily is not apparent in Horres et al. (2000), although there is a group of Pitcairnioideae genera evident, 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 Givnish et al. 2007).

For the association of Ayensua with Brocchinia and the phylogeny of the clade, see also Givnish et al. (1997) and Horres et al. (2000). For a morphological study of Puya subgenus Puya, see Hornung-Leoni and Sosa (2008). For relationships within Bromelioideae, see Horres et al. (2007), 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). For other phylogenetic studies, see Crayn et al. (2000), and Givnish et al. (2004b: ndhF).

Classification. The classic monograph of the family is that by Smith and Downs (1974, 1977, 1979), even if supraspecific groups are changing somewhat. The subfamilial classification of Givnish et al. (2008a) is followed here; see also the World Checklist of Monocots. Generic limits need attention. Thus within Bromelioideae, Aechmea is hopelessly polyphyletic (Schulte et al. 2009) and generic limits are generally unclear (Horres et al. 2007).

Rapateaceae [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 Anarthriaceae-Poacaeae 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), Mayacaceae, undifferentiated (Stevenson 1998), 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. Whatever its state of differentiation, the embryo is small and rather broad.

RAPATEACEAE Dumortier, nom. cons.   Back to Poales

Plants rhizomatous, Al accumulators; some vascular bundles amphivasal; vessels in leaf?; mucilage cells +; cuticular wax with wax globules or wax 0, stomatal guard cells dumbbell-shaped; leaves (spirally) two-ranked, (petiole + lamina), sheath distinct, open or asymmetrical and conduplicate, uniseriate [slime-secreting] colleters +; inflorescence scapose, axis usu. indeterminate, units cymose, capitate (head subtended by spathaceous bracts), flowers with several basal "bracteoles", large; C basally connate; A basally connate, adnate to C or not, porose, anther wall of the Reduced type, endothecial thickenings at apex of anther only (0), microsporogenesis simultaneous [tetrads tetrahedral], 1-many (basal) apotropous ovules/carpel, micropyle bistomal, (several antipodal calls), nucellar epidermal cells often radially elongated, outer integument 3-10 cells across, funicular obturator +, style +, stigma capitate; fruit a septicidal capsule; 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; n = 11 [Maschalocephalus]; 26; seedling?

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; 1 ovule/carpel; seeds ovoid-oblongoid, (with papillate apical appendage).

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

2. Monotremoideae Givnish & P. E. Berry

1 ovule/carpel; seeds ovoid-oblongoid, white-granulate [muriculate], with flattened apical appendage.

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); seeds prismatic, pyramidal, lenticular or crescent-shaped.

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

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

Evolution. Stem-group Rapateaceae are dated to ca 112 million years before present, divergence within the crown group to ca 79 million years before present (Janssen & Bremer 2004). Maschalocephalus dinklagei, the only African representative of the family, may have arrived there by long distance dispersal (Givnish et al. 2004a).

Chemistry, Morphology, etc. Septal nectaries seem not to occur in Rapateaceae except Monotremeae, but there are also reports of humming bird pollination of genera other than Monotremeae (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 (1969); for ovules and seeds, see Venturelli and Bouman (1988).

Phylogeny. Givnish et al. (2004a) provide a phylogeny of the group and discuss its biogeography.

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 +); pollen trinucleate, septal nectary 0, ovules tenuinucellate.

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); these glucans are sometimes pesent in only very small amounts. Rapateaceae were not examined.

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

Evolution. 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; see also Moore & Donoghue 2009).

Chemistry, Morphology, etc. Judd et al. (2002) note that the four families of Poales they mention - scattered through this part of the tree - have nuclear endosperm. 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 spiral, also two-ranked; inflorescence terminal (axillary), scapose, with involucral bracts; (flowers monosymmetric, 2-merous); C clawed; A adnate to and opposite C, exothecium +, pollen more or less spiny, (ovary with commissural [?nectariferous] appendages); seed operculum ["embryostega"] +, tegmic in origin, cuticular layer between testa and tegmen.

Evolution. Eriocaulaceae and Xyridaceae may have diverged ca 105 million years before present, the crown group of the former beginning to diversify ca 58 million years before present and that of the latter ca 87 million years before present (Janssen & Bremer 2004).

Chemistry, Morpology, etc. 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. There may have been independent evolution of an androecium consisting of three antepetalline stamens in the two families, which would then be a feature apomorphic for both Eriocaulaceae-Paepalanthoideae and Xyridaceae.

ERIOCAULACEAE Martynov, nom. cons.   Back to Poales

(Vessel elements with scalariform perforation plates); stem with endodermis; calcium oxalate crystals +; leaf bundle sheath cells large, without chloroplasts; hairs common, various, on vegetative parts with foot cell and bulbous persistent usually dark colored basal cell; cuticle waxes as aggregated rodlets; leaf sheath not distinct; plants mon(di)oecious; receptacle ± flat, scape spirally twisted, with closed basal sheath; flowers small; P with single trace, median K adaxial, K open (connate), C scarious, staminate flowers: (A dorsifixed), tapetum cells uni(bi)nucleate, (microsporogenesis simultaneous), pollen spiraperturate; carpellate flowers: staminodes common, 1 pendulous straight ovule/carpel, micropyle endostomal, antipodal cyst [formed by fusion of antipodal cells] +, hypostase +; P persistent; seeds endotestal, the anticlinal walls prominent, endotegmen tanniniferous; radicle 0; n = 9, 15, 20, 25; (ORF 2280 present).

10[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). 2 groups below.

1. Eriocauloideae

Plants usu. of aquatic habitats; roots and leaves with aerenchyma; C free, with black tips, glandular; staminate flowers: A 4-6, adnate to C.

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

2. Paepalanthoideae

Plants usu. terrestrial; (aerenchyma +); C often connate, (0); staminate flowers: (A bisporangiate/monothecal by fusion; antesepalous staminodes +), nectariferous pistillode +; carpellate flowers: commissural stylar appendages +, carinal styles/stigmas not vascularized, commissural.

9/760: Paepalanthus (485), Syngonanthus (200). New World, but esp. tropical South America.

• 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. The dark-colored glands on the petals of Eriocaulon may be nectar-producing. Rosa and Scatena (2003) suggest that in at least some Paepalanthoideae the pistillode (in staminate flowers) and carinal nectariferous appendages on the gynoecium (carpellate flowers) are nectariferous (see also Rosa & Scatena 2007; cf. Ramos et al. 2005); the nectary in both cases is made up of much elongated epidermal cells (Oriani et al. 2009).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 the scape is not twisted, although it is also short; at the base is a sheathing adaxial prophyll that is shortly connate 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). The basal part of the corolla may become secondarily free. When the style is commissural, as in Paepalanthoideae, it is unvascularised; the ovarian appendages of Syngonanthus, etc., are in the position of the style of Eriocaulon, and both are vascularised (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.

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

Much general information is taken from Unwin (2004), also from Stützel (1998), that on inflorescence and flower from Stützel (1987), embryology and seed development are summarized in Scatena and Bouman (2001) and Coan and Scatena (2004), floral anatomy is described by Rosa and Scatena (2003), and pollen morphology detailed by de Borges et al. (2009).

Phylogeny. Support for the monophyly of Eriocauloideae and Paepalanthoideae sampled was good (Unwin 2004: three genes).

Classification. Generic limits in Paepalanthoideae are in part unclear. See the World Checklist of Monocots for a listing of species.

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

(Plant caulescent; monopodial); anthraquinones +; vascular bundles amphivasal; cuticle with insoluble [organic solvent] secretion; leaf sheath distinct; (flower monosymmetric), K (2 carinate), the median [abaxial] membranous, deciduous, or all persistent, C more or less clawed, ephemeral, connate or not, A extrorse or latrorse, (free; sporangia connate), anther wall of the Reduced type, exothecium +, endothecial thickenings spiral, many ovules/carpel, micropyle?, stigma often complex and lobed/infundibular; seed coat testal and tegmic, tegmen mechanical, (operculum chalazal); deletions in ORF 2280 region [?whole family].

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

1. Xyridoideae

Leaves distichous, equitant and isobifacial [oriented edge on to the stem], ligulate; (A 6), (endothecium lacking thickenings), tapetal cells binucleate [Xyris], pollen elongate, not spiny, (bisulcate), staminodia 3, branched and with moniliform hairs on branch ends, ovules straight, placentation (intrusive) parietal; 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). [Photo - Xyris Flower, Infructescence © H. Wilson.]

Mucilage is secreted by hairs in the leaf axils of Xyris (cf. Mayacaceae?).

2. Abolbodoideae

Leaves spiral (distichous, whether or not equitant, isobifacial - Achlyphila); (inflorescence branched; open - Achlyphila; with 1 or more pairs of opposite bracts along the scape - Achlyphila, Abolboda); (K 2 - Abolboda), (A introrse), staminodes usu. 0 (filiform - Abolboda); pollen spherical, inaperturate: G with vascularised carinal [non-commissural] appendages on ovary, (0 - Achlyphila), style often solid; ovules anatropous (slightly campylotropous; crassinucellate), micropyle bistomal [Aratitiyopea]; (exotesta mechanical - Orectanthe); 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 sometimes 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. The family apparently lacks mycorrhizae.

Chemistry, Morphology, etc. The scape of Xyris is sometimes spirally twisted (cf. 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. Collar rhizoids are not drawn in Tillich (1994).

Additional information is taken from Carlquist (1960: general, inc. seed anatomy [operculum]), Tomlinson (1969: vegetative anatomy), Tiemann (1985), Stützel (1990), Kral (1972, 1998), Rudall and Sajo (1999: flower and seed), Sajo and Rudall (1999: leaf anatomy), Scatena and Bouman (2001: seed operculum), Judd et al. (2002: general), Benko-Iseppson and Wanderley (2002: cytology), Campbell (2004: much information) and Campbell and Stevenson (2008: floral morphology, esp. Aratitiyopea).

Phylogeny. There are suggestions that Xyridaceae may not be monophyletic (Michelangeli et al. 2003; Davis et al. 2004, support very weak), 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 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.

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

MAYACACEAE Kunth   Back to Poales

Monopodial marsh plants; vessels also in leaf; stem with endodermis; SiO₂ bodies 0; stomata with oblique cell divisions; leaves flat, apically bidentate, univeined, without a distinct sheath, uniseriate colleters +; flowers axillary, prophyll broad; C ± clawed; A 3, opposite sepals, porose, anther wall of the Reduced type, with exothecium, endothecium lacking thickenings, tapetal cells uninucleate, placentation parietal, 2-30 straight ovules/carpel, hypostase +, stigmatic lobes small; seed operculum ["embryostega"] +, tegmic in origin, cuticular layer between testa and tegmen, exotestal cells with 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).

• 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. 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. 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.

Some information is taken from Tomlinson (1974: stomata), Thieret (1975: general), Venturelli and Bouman (1986: ovule and seed), Stevenson (1998: general), 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 +; trichoblasts from distal cell of pair; starch grains pteridophyte-type, amylophilic; stem angled, leaves 3-ranked, sheaths closed; inflorescence racemose; flowers small, T scarious, undifferentiated, microsporogenesis simultaneous [tetrads tetrahedral], pollen in tetrads, porate, trinucleate, ovules anatropous, crassinucellate, (outer integument ³3 cells across), micropyle endostomal, style short, branches long; seeds testal-tegmic; chromosomes with diffuse centromeres; seedling collar inconspicuous, with rhizoids.

Evolution. Divergence of this clade can be dated to ca 103 million years before present (Janssen & Bremer 2004).

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. Roalson et al. (2008) and Hipp et al. (2009) discuss chromosome evolution in the clade; although diffuse centromeres are a apomorphy for the whole group, it is only in Carex that this is accompanied by considerable variation in chromosome number. A three nucleotide deletion in the atpA gene also characterises this group (Davis et al. 2004).

THURNIACEAE Engler, nom. cons.   Back to Poales

Root stock upright, or trunk-forming; flavone C-glycosides +; vessel elements with scalariform perforations; stem bundles amphivasal [Prionium], SiO₂ also in parenchyma (0 - Prionium); cuticular waxes as aggregated rodlets; leaf margin serrate, (vascular bundles in pairs, abaxial inverted - Thurnia); stem angled; inflorescence capitate and involucrate or a much-branched panicle; perianth tube short, tapetal cells?, pollen grains ulcerate, exine granular, 1-few ascending ovules/carpel, [micropyle zig-zag], hypostase +, styles separate, or style with long branches; seeds arillate, testa of sclerenchymatous fibers and unthickened cells, tegmen tanniniferous [Thurnia]; phanomer [photosynthetic unifacial cotyledonary hyperphyll], hypocotyl + 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 stems, serrate leaves, and pentacyclic flowers with scarious perianth.

Evolution. Stem-group Thurniaceae are dated to ca 98 million years before present, the crown group diverged ca 33 million years before present (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 Oxychloe 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. This clade diverged from Thurniaceae ca 98 million years before present, itself splitting ca 88 million years before present (Janssen & Bremer 2004; Besnard et al. 2009b); a less likely age for the clade is 39-28 million years before present (Wikström et al. 2001). The clade [Juncaceae + Cyperaceae] is notably speciose (Magallón & Sanderson 2001).

Mycorrhizae appear to be absent, but cluster roots are common. 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); cf. also the distribution of the parasitic Claviceps itself.

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).

Phylogeny. Muasya et al. (1998) suggested that Oxychloe (Juncaceae) 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 Oxychloe within Cyperaceae. The relationships of the latter genus in particular 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 & Vl&ctilde;ek 2007); part of the problem seems to have been caused by the identity of the material from which early molecular samples of the genus 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; SiO₂ bodies 0 (sand - Juncus); (leaves [spirally] two-ranked); sheath usu. open (auriculate; ligule +), often unifacial; (flowers single); (flowers 2-merous; imperfect), (T large - Marsippospermum), tapetal cells uninucleate, pollen grains central in loculus, ulcerate, (placentae parietal), 1 basal to many central ovules/carpel, (outer integument 4 cells across - Juncus), funicular obturator [hairs] and hypostase +/0, style branched (styles separate), stigma elongate; seed with (mucilaginous) exotesta and endotegmen; endosperm helobial; phanomer [photosynthetic unifacial cotyledonary hyperphyll] + (0), hypocotyl +; 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; Balsev 1996, still incomplete).

• 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.[Photo - Juncus Inflorescence] [Photo - Luzula Flower]

Evolution. Stem-group Juncaceae are dated to ca 88 million years before present, the crown group diverge ca 74 million years before present (Janssen & Bremer 2004).

Chemistry, Morphology, etc. In Luzula stamens are opposite individual tepals (Payer 1857) and the flowers may have the adaxial tepal in the outer whorl, and also a variety of bract structures associated with the flower (Eichler 1874). Some information is taken from Balslev (1998); for anatomy, see Cutler (1969), for some chemistry, see Williams and Harborne (1975).

Phylogeny. For a phylogeny, with Juncus perhaps being paraphyletic, see Drábková et al. (2003) and Roalson (2005). Drábková and Vlcek (2009) also 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.

CYPERACEAE Jussieu, nom. cons.   Back to Poales

(Vesicular-arbuscular mycorrhizae +); aurones, flavonoid sulphates, flavone C-glycosides, tricin, kestose and isokestose storage oligosaccharides [fructans] +; (velamen +); SiO₂ bodies smooth, conical, with pointed apices, attached to walls; guard cells dumb-bell shaped; cuticular waxes as aggregated rodlets; leaves (two-ranked; tetrastichous; spiral; petiole + lamina), sheath with (contra)ligule; plants monoecious or polygamous; stems solid; inflorescence a panicle of spikelets; T (connate), variously reduced; A (1-)3(-6 or more), (connate), tapetal cells bi-multinucleate, (pollen grains 2-celled), pseudomonads, with distal pore [ulcus], (G [2]), (gynophore +), 1 basal ovule/flower, micropyle?, micropylar/funicular obturator +, style branches long; fruit an achene, (with bristles, etc.); testa and tegmen thin, ± coalescent, exotesta with SiO₂ bodies, other testal layers fibrous; endosperm nuclear, 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]/4350. World-wide (Map; Hultén 1961; Vester 1940). [Photo - Carex Carpellate Inflorescence, Eleocharis Spikes.]

1. Mapanioideae

Phytoliths uncommon; flowers pseudanthia, with stamens in axils of bracts surrounding carpellate flowers[???], pollen grains central in loculus, (micropyle bistomal, zig-zag - Hypolytrum).

6/140: Mapania (80), Hypolytrum (50). Largely tropical.

Synonymy: Mapaniaceae Shipunov

2. Cyperoideae

Fine roots dauciform; phytoliths common; T = scales, bristles, 0 (inner tepals clawed), pollen grains peripheral in loculus, obovoid, also with 3-6 lateral pores/colpi (pantoporate).

92/4210: Carex (1776), Cyperus (300), Fimbristylis (250), Rhynchospora (250), Scirpus (200), Scleria (200), Eleocharis (120), Bulbostylis (100), Schoenus (100), Isolepis (70). Worldwide.

Synonymy: Kobresiaceae Gilly, Papyraceae Burnett, Scirpaceae Batsch

• 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. Stem-group Cyperaceae are dated to ca 88 million years before present, the crown group diverged ca 76 million years before present (Janssen & Bremer 2004; Besnard et al. 2009b). 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 - cf. Cyperoideae).

Cyperaceae (and Poaceae and Juncaceae) may be common in tundra habitats, communities dominated by these groups being notably common during the last glacial maximum (Bigelow et al. 2003). Other habitats in extreme climates may be dominated by Cyperaceae. The some 450,000 square kilometers between 3,000 and 5960 m altitude on the Tibetan plateau dominated by Kobresia pygmaea may be of more recent origin; this community may have reached its current extent since the spread of the Tibetan empire in the seventh century CE (Miehe et al. 2008). Cyperaceae, as with other plants in the tundra habitat, often lack mycorrhizae and may take up nitrogen predominantly in an organic form, although some Cyperaceae can take it up in an inorganic form (Raab et al. 1999; Miller at al. 1999 for mycorrhizae in Carex). Largely ascomycetous fine endophytes are commonly found in plants from tundra habitats (Higgins et al. 2007). Dauciform roots, with particularly well developed root hairs, occur in Cariceae and Rhynchosporeae, and some species of non-mycorrhizal Carex have distinctive, bulbous-based root hairs (Miller et al. 1999).

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

About one third of the family have C₄ photosynthesis, with perhaps six origins within the family as well as some reversals to C₃ photosynthesis, and it is possibly involved in increasing the efficiency of the use of nitrogen in plants with submerged leaves (Soros & Bruhl 2000; Bruhl & Wilson 2008). Besnard et al. (2009b) suggested that evolution of C₄ photosynthesis had occured since about 19.6 million years ago, with genetic changes in the important enzyme phosphoenolpyruvate carboxylase occuring in parallel.

A few taxa like Rhynchospora anomala are dessication-tolerant and arborescent; their adventitious roots, which make up the trunk along with the persistent leaf bases through which these roots run, have a well-developed velamen (Porembski 2006). A number of Cyperoideae (but not Scirpeae) have dauciform roots, carrot-shaped roots which develop a dense covering of very long root hairs; these are believed to help in phosphorus uptake by the plant when growing in phosphorus-poor soils (Shane et al. 2005: some Juncaceae may also have such roots). Epidermal cells in such roots are elongated at right angles to the long axis of the root (Shane et al. 2005).

Waterway et al. (2009) discuss ecological diversification in Cariceae; there are widespread wetland species and often more geographically restricted forest taxa.

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

Chemistry, Morphology, etc. Zhang et al. (2004) have recently demonstrated that spikelet structure in Schoeneae, at least, is sympodial, although that of Cyperoideae is indeterminate (Vrijdaghs et al. 2005c). The stamens are shown as being opposite the outer perianth whorl (Bruhl 1991) or the angles of the gynoecium (Goetghebeur 1998). 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 from which other more derived developmental morphologies in Cyperoideae can be related (Vrijdaghs et al. 2009). Eriophorum (Cyperoideae) has its distinctive hairs arising centripetally on a perianth ring-primordium (Vrijdaghs et al. 2004b). For the literature on the possible pseudanthial nature of some flowers in Cyperaceae, see Bruhl (1991), who found that the non-sporiferous structures in the taxa he studied were ouside the stamens, so probably representing perianth parts (see also Vrijdaghs et al. 2004a; Richards et al. 2005 - flowers of Exocarya sclerioides [a mapaniid] pseudanthial). The median carpel in Carex is adaxial (Eichler 1875), i.e. in the inverted position (see also Spichiger et al. 2004).

For a vast amount of systematic information, see Bruhl (1995), for further general information, see Naczi and Ford (2008). For the prophyll, see Blaser (1944), for floral morphology, see Goetghebeur (1998), for pollen, see van Wichelen et al. (1999), for the gynophore, etc., see Vrijdaghs et al. (2005b), for propagule dispersal, see Allessio Leck and Schütz (2005), 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 inflorescence morphology, see Vrijdaghs et al. (2008), for a nrDNA insertion, see Starr et al. (2008), for ovule and seed development, see Coan et al. (2008), and for a survey of pollen morphology, see Nagel et al. (2009).

Phylogeny. Mapanioideae are sister to the rest of the family, while Carex, sister to Eriophorum, is embedded in Cyperoideae, the other clade (Simpson et al. 2003, esp. 2008). Naczi (2009) discusses the use of morphological characters in phylogenetic analyses; tricky because of the highly derived floral morphologies. Trilepideae are sister to all other Cyoperoideae (Muasya et al. 2009a). Within Cariceae, phylogenetic studies are beginning to resolve relationships (Reznicek 1990 and associated papers; Yen & Olmstead 2000; Yen et al. 2000; Roalson et al. 2001; Starr et al. 2004, 2006; Waterway & Starr 2008). Carex is paraphyletic, as has been demonstrated by several studies that are also clarifying relationships within this huge and difficult clade (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). Conventional wisdom in which a highly compound inflorescence is the plesiomorphic condition for Carex, taxa with simple branches being derived, perhaps several times, seems the exact opposite of what actually happened (Ford et al. 2006); again, evolution is not necessarily complex -> simple! Cyperus is also paraphyletic (Muasya et al. 2002). For the relationships of Carpha and other Schoeneae, see Zhang et al. (2007), and for relationships within Rhynchosporeae, see Thomas et al. (2009).

Classification. Carex is paraphyletic (see above) and genera like Kobresia, Cymophyllus and Uncinia are probably to 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. For 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]]]: plant rhizomatous; 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 [cf. arm cells of some Poaceae?]); leaves two-ranked, with sheath; bracteoles 0; flowers small, imperfect, T membranous, undifferentiated, endothecial wall thickenings girdle-like, scrobiculate [minute pores penetrating tectum and foot layer], monoporate, annulate ["ulcerate"], 1 apical straight tenuinucellate ovule/carpel, style branches long, stigmas plumose, receptive cells on multicellular branches; collar rhizoids +.

Evolution. This clade begins to diversify ca 109 million years before present, originating at ca 112 million years before present (Janssen & Bremer 2004), but note that in their study the topology of this part of the Poales differs from that in the tree above, while Wikström et al. (2001) suggest an origin only 49-45 million years before present, but again the topology of the tree from which this estimate was taken is rather different from that used here.

This is a notably speciose clade (Magallón & Sanderson 2001) with over 10,000 species. However, there is considerable asymmetry in family size within the clade, with most species belonging to Poaceae, the second most species-rich family (Restionaceae) having only some 520 species. Furthermore, given the number of species-poor clades that are successively immediately sister below the PACCMAD and BEP clades (Poaceae) - five - diversification is perhaps more properly described as diversification in the PACCMAD and BEP clades within Poaceae (see also Linder & Rudall 2005 for diversification).

Chemistry, Morphology, etc. Although it is suggested above that an apomorphy for the clade is to have imperfact flowers, the situation is unclear, especially in the Flagellariaceae to Poaceae part of this clade. 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 a parietal cell and as being tenuinucellate and the pollen as being trinucleate for the whole group by Givnish et al. (1999, cf. 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), and 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 flavonoids of Anarthriaceae, Restionaceae and Ecdeiocoleaceae, see Williams et al. (1997); the variation is complex and needs to be reevaluated in light of the changed position of the last family. Linder and Ferguson (1985) discuss variation in pollen morphology.

Phylogeny. A recent analysis of variation in 26S rDNA suggests that Dasypogonaceae may 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, and 18S etc., do not suggest such a grouping, so pending further study Dasypogonaceae remain unplaced at the base of the commelinids (q.v. for further discussion). Davis et al. (2004: very weak support) found Flagellaria to group with Mayacaceae, etc., rather than with the other familes of the clade recognised here, while Graham et al. (2005) obtain a set of relationships [Flagellariaceae [Restionaceae [Ecdeiocoleaceae [Poaceae]]], perhaps a branch length or sampling problem.

Anarthriaceae [Centrolepidaceae + Restionaceae]: root hairs originating from any epidermal cells; chlorenchyma with peg cells; plant dioecious; A 3, opposite inner P, dorsifixed; phanomer [photosynthetic unifacial cotyledonary hyperphyll] +.

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

(Flavonol glycosides +); root hairs lignified; SiO₂ 0; stomata in grooves; leaves ligulate; plant dioecious, culm branched, inflorescence racemose; staminate flowers: pollen operculate; carpellate flowers: G opposite outer P, 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. Stem-group Anarthriaceae are dated to ca 96 million years before present, the crown group diverge ca 55 million years before present (Janssen & Bremer 2004).

Chemistry, Morphology, etc. The three genera are rather different. Anarthria has equitant isobifacial leaves, stomata in grooves, a deciduous spathe, and n = 11. 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, 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; pollen microverrucate - and are associated with Anarthria (Briggs et al. 2000, see also papers in Meney and Pate 1999). Stigma papillae in Anarthria? Microsporogenesis?

Much information is taken from Briggs and Johnson (2000); note that no comparison is made there with Ecdeiocoleaceae and no hierarchical information is conveyed by having three families for three genera. Other information is taken from Cutler and Airy Shaw (1964), Linder and Rudall (1993) and Linder et al. (1998).

Phylogeny. Hopkinsia +andLyginia are sister taxa and are associated with Anarthria (Briggs et al. 2000, see also papers in Meney and Pate 1999). However, the sampling of non-Australian Restionaceae is poor, and Linder et al. (2000) even suggested that these genera are Restionaceae, albeit perhaps sister to the rest - they have the distinctive culm anatomy of that family, and Lyginia has starch in the embryo sac, like Restionaceae (Hopkinsia is unknown).

Classification. Putting the three genera in three separate families seems a bit much, although the three genera are morphologically quite distinct.

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

Centrolepidaceae + Restionaceae: mycorrhizae 0; anthers bisporangiate/monothecal; pollen pore not annulate, margin irregular; embryo sac with compound starch grains, cells of nucellar epidermis anticlinally elongated.

Evolution. The group lacks mycorrhizae.

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 and broader studies are needed. As things stand, a position sister to Restionaceae is possible (Linder & Caddick 2001) as well as one - but with weak support - within the family (Bremer 2002). In a recent study Centrolepidaceae and Restionaceae were sister taxa in parsimony analyses of trnK and trnL-F, while in Bayesian analyses of these genes, and also in rbcL analyses, the relationships [Restionoideae [Sporadanthoideae [Leptocarpoideae + Centroplepidoideae]]] were recovered (Briggs & Linder 2009; Briggs et al. 2009); the latter set of relationships seems more likely. It may be relevant that the pollen apertures of Australian Restionaceae in particular are like those of Centrolepidaceae (Chanda 1966).

CENTROLEPIDACEAE Endlicher, nom. cons.   Back to Poales

± Caespitose herbs; vessels in stem and leaf; SiO₂ ?0; plants monoecious; epidermis with hairs and papillae; leaves unifacial (ligulate); inflorescence scapose, capitate and with inflorescence bracts or spicate; P 0; staminate flowers: A 1-2; carpellate flowers: G [1-14(-45)]; ovules with antipodals usu. binucleate, nucellar cap 0; fruit abaxially dehiscing or indehiscent; endotegmen 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. Estimates of the age of the Centrolepidaceae clade range from 45-97 million years before present depending in large part exactly where it is placed in this part of the tree (Janssen & Bremer 2004).

Centrolepidaceae may be neotenous Restionaceae, but their position with regard to that family needs to be clarified (e.g. Linder et al. 2000).

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 sensu stricto 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. 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 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; perhaps cells in the nucellar epidermis have divided.

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

Root hairs usu. persistent, lignified; rhizome with endodermoid sheath; stem with complete cylinder of sclerenchyma, bundles inside, both peripheral and medullary; vessels in stem (and leaf); protective cells [lignified chlorenchymatous cells] lining substomatmal cavities +; leaves much reduced (sheath closed); plant di(mon)oecious, flowers in 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; carpellate flowers: P variable; G opposite outer P, (only 1 fertile), common style short or 0; ovules (crassinucellate - Alexgeorgea; micropyle endostomal - Willdenowia, some Leptocarpus), large starch bodies surrounding polar nuclei, hypostase +; exotesta persistent; (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). [Photos - Collection. Dovea tectorum is properly Chondropetalum tectorum]

1. Restionoideae Bartling

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

17/350: 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; ovules with antipodals proliferating; (fruit a soft-walled nut); young seed coat tanniniferous.

9/300: Restio (95), Ischyrolepis (48), Elegia (50), Thamnochortus (35). Madagascar, Africa south of the Sahara, especially the Cape Region. [Photo - Elegia, Habit.]

1b. Willdenowieae Masters

SiO₂ bodies usually in sclerenchyma cylinder only; ridges of sclerenchyma often alternate with vascular bundles, (lignified chlorenchyma cells extending from ridges); chlorenchyma cells often radially short and squat; styles 2; 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, proanthocyanidins rare, flavones diverse, sulphated flavonoids +; chlorenchymatous cells palisade; pollen grains with pores 8-25 µm across, not annulate, irregular, thickened foot layer 0 [cf. 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 usually aggregated into spikelets.

Evolution. Stem-group Restionaceae are dated to ca 96 million years before present, the crown group diverge ca 74 million years before present (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 million years before present (Hardy et al. 2004; 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 million years ago separating what became eastern and western clades (Crisp & Cook 2007)

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 (cf. 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 phosphorus-poor environments develop analagous structures that are believed to facilitate phosophorus uptake by the plant. Interestingly, one study suggested that the total root length of the grasses tested was considerably greater than that of Restionaceae, although the dense root hairs of Restionaceae were not taken into account (Bell et al. 2000). [What is the relationship with lignification of root hairs?]

Myrmecochory is common in the African clade 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 Kircher (1986; he does not draw the guard cells as being dumbbell-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. (2009).

Classification. For the classification of Restionaceae and characterization of the subfamilies, see Briggs and Linder (2009); Leptocarpoideae have been pulverized.

Synonymy: Elegiaceae Rafinesque

Flagellariaceae [[Joinvilleaceae + Ecdeiocoleaceae] Poaceae]: trichoblasts from distal cell of pair; leaf blade with cross veins, ligule +; inflorescence paniculate, branches with adaxial swellings; flower type?; fruit indehiscent, fleshy; cotyledon not photosynthetic.

Evolution.Net venation, animal-dispersed propagules and tolerance of shady habitats are linked in some members of this group (Givnish et al. 2005).

Chemistry, Morphology, etc. 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). 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.

Phylogeny. 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), a not dissimilar result to that obtained by Davis et al. (2004). However, in another two-gene study, although both genes were chloroplast genes, Marchant and Briggs (2007: both genera of Ecdeicoleaceae included) found strong support for a sister group relationship between Joinvilleaceae and Ecdeiocoleaceae. Monophyly of the whole clade, and other relationships in it, were also strongly supported.

FLAGELLARIACEAE Dumortier, nom. cons.   Back to Poales

Dichotomising stem apices; flavonols +; endodermis radially elongated; SiO₂ associated with bundles only; neighbouring cells of stomata with oblique divisions; prophylls lateral; leaves with terminal tendril, base ?auriculate, sheath also closed; flowers perfect, P pseudo-uniseriate, pollen 2-nucleate, ovule crassinucellate, micropyle endostomal, embryo sac bisporic, eight nucleate [Allium-type], style solid; fruit a drupe, seed coat adnate to fruit, exotestal; 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. Flagellariaceae may be ca 108 million years old (Janssen & Bremer 2004: but note the topology).

Chemistry, Morphology, etc. Flagellaria indica may have dichotomising stem apices (Tomlinson & Posluszny 1977). There is disagreement as to whether or not the ORF 2280 gene is present - or perhaps there is variation... (cf. Hahn et al. 1995 and Katayama & Ogihara 1996). The stigma has "multicellular papillae". Since the seed coat is adnate to the fruit wall, I suppose the fruit is a caryopsis s.l....

Some information is taken from Rudall and Linder (1988: embryology), Tillich (1996), Appel and Bayer (1998: general), Tillich and Sill (1999: general), and Sajo et al. (2007: style).

[Joinvilleaceae + Ecdeiocoleaceae] Poaceae: SiO₂ bodies cubic; epidermis with microhairs; foliar epidermis with long and short cells [latter SiO₂-containing]; guard cells dumbbell-shaped; fusoid cells [large colorless cells in central mesophyll] +; stem hollow [level?]; endothecial cells with girdle thickenings [?Poaceae], nucellar cap +; first seedling leaf lacking lamina [possible]; 28 and 6.4 kb chloroplast genome inversion +.

Phylogeny. This clade may have originated ca 103 million years before present (Janssen & Bremer 2004), although note that Flagellariaceae are not associated with it in that analysis; it diversified only ca 90 million years before present.

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. For chloroplast genome inversions, see Doyle et al. (1992); the 6.4 kb inversion has recently been reported in Ecdeiocoleaceae (Michelangeli et al. 2002, 2003; Marchant & Briggs 2007).

Joinvilleaceae + Ecdeiocoleaceae: ?

JOINVILLEACEAE Tomlinson & A. C. Smith   Back to Poales

Arm cells 0; leaves plicate, auriculate or ligulate; flowers perfect, outer T hooded, ovule type?, embryo sac bisporic; fruit a drupe; P persistent; n = 18; rps14 gene to nucleus, pseudogene remaining in mitochondrion; 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. Joinvilleaceae may be some 90 million years old (Janssen & Bremer 2004).

Chemistry, Morphology, etc. The outer tepals may have only a single trace (Newell 1969). Some information is taken from Newell (1969: revision) and Bayer and Appel (1998: general).

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

SiO₂ as sand; vessels?; stomata in grooves; leaves reduced, sheath closed, auriculate; plant monoecious, culm branched, inflorescence branch swellings?, with "spikelets"; flowers imperfect; P 2 conduplicate and keeled + 4 flat, staminate flowers: A 4 [Ecdeiocolea], pollen with operculum, wall without scrobiculi, with intraexinous channels; carpellate flowers: (embryo sac tetrasporic - Ecdeiocolea); fruit 1-seeded, achene or capsule; ?perisperm +; exotestal cells large; n = ca 24, 32, 33; seedling?

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

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

Chemistry, Morphology, etc. In Georgeantha only the two adaxial calyx members are keeled, while 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) 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, major constituent (1,3:1,4)-ß-D-glucans; lignins acylated with p-coumarates [?level]; sieve tube plastids also with rod-shaped protein bodies, P-proteins 0; cuticle waxes as aggregated rodlets; leaves pseudopetiolate, supervolute(-plicate), midrib +; two adaxial outer T distinct, abaxial smaller; A centrifixed [?level], pollen grains central in loculus, with operculum, wall without scrobiculi, with intraexinous channels; G (open in development), with 1 central amphitropous or hemianatropous crassinucellate ovule [funicle short], micropyle endostomal, supernumerary antipodals +, style solid [?level]; fruit an achene, the testa closely adherent to pericarp [= caryopsis], hilum long [reverses]; peripheral layer of endosperm meristematic, embryo lateral, long, well differentiated, plumule lateral; primary root 0, collar [epiblast, the ligule of the cotyledon] conspicuous; n = ?; expansion of the inverted repeat [level?], chloroplast genome with [third!] trnT inversion in the single-copy region, only 17 introns [those in clpP and rpoCI genes absent], duplication of AP1/FUL genes [= FUL1 and FUL2], rps14 gene to nucleus, pseudogene remaining in mitochondrion, intragenomic translocation of chloroplast rpl23 gene.

668/10035. Thirteen subfamilies below. Worldwide (map: from Vester 1940; Hultén 1961). [Genera List] [Photo - Flower]

1. Anomochlooideae Potzdal

Pseudopetiole with an apical pulvinus; ligule as a fringe of hairs; inflorescence branches cymose, two "bracts" along each branch unit, two more "bracts" below each flower; flowers perfact; P 2 (3) + 3; or flowers spirally arrranged along racemose axis, with several spiral "bracts" below each flower, possibly 3 + 3, the latter coriaceous; A sub-basifixed, basally connate, not dangling, [latrorse, anther wall development of the Reduced type, endothecium lacking thickenings, microsporogenesis simultaneous, stigma not plumose - all Streptochaeta]; n = 11, 18; first seedling leaf lacking lamina.

2/4. Central America to S.E. Brasil, scattered, forests (map: from Judziewicz et al. 1997).

Synonymy: Anomochloaceae Nakai, Streptochaetaceae Nakai

Pharoideae + Puelioideae + PACCMAD + BEP clades [the spikelet clade]: leaves with ligules; inflorescence of laterally compressed, racemose, pedunculate spikelets, few-flowered units with two sterile basal bracts [= glumes, spikelet bract + prophyll], flowers two-ranked, each with lemma and palea [?= bract and 2 adaxial connate outer-whorl tepals]; lodicules [inner whorl?] 3 [median member adaxial]; n = 12; 1 bp deletion in the 3' end of the mat K gene.

2. Pharoideae L. G. Clark & Judziewicz

Microhairs 0; leaves resupinate, lateral veins oblique; plants monoecious; spikelets 1-flowered; staminate flowers: A 6, latrorse, wall of the Reduced type, endothecium lacking thickenings [both Pharus], carpellate flowers: micropyle bistomal and style solid [Pharus]; coleoptile [= first seedling leaf] with lamina.

3/14. Pantropical, in forests (map: from Judziewicz 1987; Judziewicz et al. 1997).

Synonymy: Pharaceae Herter

Puelioideae + PACCMAD + BEP clades [the bistigmatic clade]: phytoliths saddle-shaped; spikelets 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

Characters?; flowers perfect; A 6; seedling leaf unknown.

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

PACCMAD + BEP clades: (benzoxazinoids, ergot alkaloids [latter synthesized by endophytes] +); arm and fusoid cells 0; foliar cross veins 0; pseudopetiole 0; flower type?; A 3, lodicules 2; G 2, styles separate; x = 12; genome duplication, 15 bp insertion in ndhF gene, disease resistance by the Hm 1 gene. Mostly non-forest.

Evolution. The age of the crown group PACCMAD + BEP clade may be (60-)52(-44) million years (Vicentini et al. 2008); Kim et al. (2009: MAD members not included) date it 67.8-50 million years.

For the Hm 1 gene, see Sindhu et al. (2008).

Panicoideae + Arundinoideae + Centothecoideae + Chloridoideae + Micrairoideae + Aristidoideae + Danthonioideae [PACCMAD clade]: phytoliths dumbbell-shaped; mesocotyl internode elongated, epiblast 0; extension of ndhF gene from the short single copy region into the inverted repeat.

For the ndhF gene, see Davis and Soreng (2008). Ca 50% of the species have C₄ photosynthesis.

[Panicoideae + Centothecoideae] Arundinoideae + Chloridoideae: 6 bp insertion in the 3' end of the mat K gene.

Panicoideae + Centothecoideae: hilum non-linear; overlapping embryonic leaf margins.

The first character could also be used to unite Panicoideae + Arundinoideae + Centothecoideae + Chloridoideae.

4. Panicoideae Link

(Fusoid cells +); microhairs elongated, slender, thin-walled; culms usually solid; spikelets dorsally compressed, rachilla 0, 2-flowered, lower flower staminate or sterile [gynoecial cell death caused by Tasselseed2], spikelet dispersed as a 1-seeded unit by disarticulation below the glumes; C₄ photosynthesis common; starch grains simple; 5 bp insertion in the rpl16 intron; n = 5 (7) 9, 10 (12, 14); germination flap +; rps14 pseudogene lost.

206/3245: Panicum (500 s.l., but polyphyletic, 100 s. str., Dicanthelium [55] - see e.g. Zuloaga et al. 2007), Paspalum (330), Setaria (150: inc. Cenchrus), Andropogon (100). Tropics to temperate.

Details of the mechanisms of C₄ photosynthesis and the morphologies associated with it are very variable in this Panicoideae, and C₄ photosynthesis has evolved more than once, with similar amino acid changes occuring in parallel in the phosphoenolpyruvate carboxylase gene (Kellogg 2000 and references; see also Giussani et al. 2001; Christin et al. 2007a, 2009a).

Synonymy: Andropogonaceae Martynov, Arundinellaceae Herter, Panicaceae Voight, Saccharaceae Martynov, Zeaceae A. Kern

5. Centothecoideae Soderstrom

Mesophyll differentiated into palisade and spongy tissues; chlorenchyma cells lobed [cf. arm cells]; style +; n = (11) 12; epiblast +.

12/32. Warm temperate to tropical forests (map: from Sánchez-Ken & Clark 2008).

Arundinoideae + Chloridoideae + Aristidoideae + Danthonioideae: ligule hairy; lemma awned; starch grains compound.

Eriachne, with ca 40 species, may be sister to this clade.

Danthonioideae + Chloridoideae: ?

6. Danthonioideae Barker & Linder

Prophylls bilobed [?distribution]; lemma awn trifid, or 3 awns; synergid cells haustorial, bases of styles well apart; hilum short; n = 6, 7, 9.

19/270: Danthonia (100), Rytidosperma (90). Widespread, but few Southeast Asia-Malesian, especially southern, Africa.

For a phylogeny of the Pentaschistis group (Danthonioideae), also character evolution there, see Galley & Linder (2007), for relationships in the subfamily as a whole, see Barker et al. (2007a) and Pirie et al. (2008).

7. Chloridoideae Beilschmied

C₄ PCK subtype (phosphoenolpyruvate carboxykinase) +; microhairs with inflated distal cells; spikelets disarticulating above the glumes; 4 bp insertion in the rpl16 intron; n = (7, 8) 9, 10; C₄ photosynthesis prevalent.

/1350: Eragrostis (300), Muhlenbergia (160), Sporobolus (160), Chloris (55). Tropical to warm temperate, more or less dry environments especially in Africa and Australia.

Within Chloridoideae, Eragrostis, Muhlenbergia and Sporobolus may be all polyphyletic. For a morphological phylogenetic analysis of the subfamily, see Liu et al. (2005), for other relationships, see papers in Aliso 23: 565-614. 2008.

Apparently the earliest name for this clade is Chondrosoideae Link, which is a sort of resurrection name - Googling it (as of 3.vii.2007) returned only Thorne and Reveal (2007), who were apparently the only people to have used it for some time, and about 42,100 returns for Chloridoideae.

Synonymy: Chloridaceae Herter, Eragrostidaceae Herter, Pappophoraceae Herter, Spartinaceae Burnett, Sporobolaceae Herter

8. Micrairoideae Pilger

Stomata with dome-shaped subsidiary cells; ligule with fringe of hairs; lemma awn +/0; embryo small, starch grains simple; n = 10; germination flap +; (C₄ photosynthesis - Eriachneae).

8/170: Isachne (100), Eriachne (35). Tropics.

Micraira has spirally arranged leaves and at least some species are resurrection plants.

For further information, see Sánchez-Ken et al. (2007).

9. Aristidoideae Caro

Lemma awn trifid, or 3 awns, awns with basal column; n = 11, 12; germination flap +; C₄ photosynthesis prevalent.

3/300-385: Aristida (230-330), Stipagrostis (50). Warm temperate, few in Europe.

10. Arundinoideae Burmeister

Hilum short; n = 6, 9, 12.

14/20-38. Temperate to tropical, hydrophytic to xerophytic.

The exact contents of this subfamily are still unclear.

Synonymy: Arundinaceae Hochst.

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

Evolution. For the evolution of a grain softness (HA-like gene) trait in the common ancestor of Ehrhartoideae and Pooideae, see Charles et al. (2009).

Phylogeny. Ehrhartoideae and Pooideae have weak to moderate support as sister taxa (Bambusoideae not included: Saski et al. 2007: see also grass Phylogeny Working Group 2001). Where exactly Streptogyneae are to be placed, whether in Bambusoideae, Ehrhartoideae, or in a separate subfamily, is unclear (Hisamoto et al. 2008).

11. Ehrhartoideae Link

(Microhairs 0); fusoid cells 0 (arm cells +); spikelets with only one carpellate floret fertile and with basal carpellate or sterile florets, glumes very small; A (1-)6, styles separate almost from the very base; n = (10, 15).

17/120: Oryza (20), Leersia (20). Widespread, esp. S. hemisphere.

Synonymy: Oryzaceae Burnett

Bambusoideae + Pooideae: ?

12. Bambusoideae Luersson

Woody; fusoid cells and strongly asymmetrically invaginated arm cells +; leaves pseudopetiolate, often with inner and outer ligules, culm leaves often very different from the others; (lodicules 3); A (2-)6(-140), (basally connate), stigmas (1-)2-3; (fruit a berry); embryonic leaf margins overlapping; first seedling leaf without lamina; n = 7, 9-12.

84-101/940-1320. Bambusa (120), Chusquea (140), Sasa (60), Phyllostachys (55), Arundinaria (50). Tropical to temperate, often in forests (map: see Sungkaew et al. 2009).

For general information, see Clark (1997), Judziewicz et al. (1997), and Judziewicz and Clark (2008), for foliar epidermis, see Yang et al. (2008a).

Synonymy: Bambusaceae Burnett, Parianaceae Nakai

13. Pooideae Bentham

Aerial branching rare at most; fructose oligosaccharides in stem; microhairs 0; stomata subsidiary cells with parallel sides; primary inflorescence branches distichous; lemma usually with 5 nerves; lodicules at most slightly vascularised, styles separate almost from the very base; hilum often short; n = (2, 4-)7[chromosomes large; core Pooideae](-13); duplication of the ß-amylase gene.

/3300. Festuca (470: inc. Lolium), Poa (200), Stipa (300), Calamagrostis (230), Agrostis (220), Elymus (150), Bromus (100). Largely N. temperate.

Although low levels of fructan accumulation, specifically levans, have been noted in many Poaceae, high levels are found only in Pooideae, but not in taxa of the basal pectinations (see Hendry 1993 for taxa involved; Pollard & Cairns 1991). It is not certain the the duplication of the ß-amylase gene is an apomorphy of (many) Pooideae. One of the copies of the gene 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 the expansion of the inverted repeat in Pooideae at the SSC/IRa boundary, see Saski et al. (2007).

Synonymy: Aegilopaceae Martynov, Agrostidaceae Burnett, Alopecuraceae Martynov, Avenaceae Martynov, Festucaceae Pfeiffer, Hordeaceae Burnett, Melicaceae Martynov, Miliaceae Burnett, Nardaceae Martynov, Phalaridaceae Burnett, Stipaceae Burnett, Triticaceae Hochst.

• Poaceae can be recognised by their leaves that have long open sheaths and ligules at the sheath-lamina junction, round and often hollow stems, 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. Stem-group Poaceae are dated to ca 89 million years before present, the crown group diverge ca 83 million years before present (Janssen & Bremer 2004: Streptochaeta included, see also Bremer 2002; dates in Wikström et al. 2001 are far younger). As to more conventional grasses (the [PACCMAD + BEP] clade), fossil spikelets assignable to them are known from the Palaeocene-Eocene boundary, about 55 million years before present (Crepet & Feldman 1991), and this estimate is broadly in line with an estimate of the age of a genome duplication in Poaceae (70-50 million years before present: Blanc & Wolfe 2004; Schlueter et al. 2004; Paterson et al. 2004; Kim et al. 2009) and other estimates like that of Vicentini et al. (2008) - (60-)52(-44) million years old. Bouchenak-Khelladi et al. 2009) suggest that grasses orignated ca 90 million years ago, the BEP clade beginning to diversify in the end Palaeocene ca 55 million years ago and the PACCMAD clade diversifying rather later towards the end of the Eocene some 37 million years ago. However, Poinar (2004) suggests that Programinis burmitis, from the Early Cretaceous some 100-110 million years before present, is an early bambusoid grass type. Although it has some vegetative features that are common in Poaceae, it does not have distinctive features of the family and so is unlikely to be included here (Caroline Stömberg, pers. comm.). 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 questioned by the discovery of well-preserved phytoliths of types to be found in the PACCMAD and BEP clades in coprolites of sauropod dinosaurs from the Late Cretaceous (71-65 million years before present) of central India (Prasad et al. 2005: there are grass pollen and macrofossils also known from this age), and this would date the origination of the clade to some 85-80 million years ago. This record, too, needs confirmation, although the enigmatic Late Cretaceous mammalian sudamericid gondwanatherians also had hypsodont teeth and there is a record of a 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 bottom line is that dates from these different lines of evidence are apparently irreconcilably in conflict (Vicentini et al. 2008).

Although the Poaceae group of families is described as being notably speciose (Magallón & Sanderson 2001), there is considerable asymmetry in family size within the clade, with most species belonging to Poaceae themselves. The second most species-rich family (Restionaceae) has only some 520 species. Furthermore, even within Poaceae given the number of species-poor clades that are successively immediately sister below the PACCMAD and BEP clades - five - calling the whole family speciose is an overstatement, rather, there has been diversification within the PACCMAD and BEP clades (see also Linder & Rudall 2005 for diversification). 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. The herbaceous habit and annual life cycle appear to be correlated with species richness (Salamin & Davies 2004; Smith & Donoghue 2008). Diversification within bamboos occured 40-30 million years before present. A factor contributing to the diversification of Pooideae may be the establishment of vernalization (Preston & Kellogg 2008), although how widely this occurs outside the subfamily is unclear.

Grasses now cover about 20% of the land surface (Sabelli & Larkins 2009 for references). Open-habitat grasses - these were mostly C₃ grasses initially - diversified taxonomically in North America in the early Oligocene ca 34 million years ago and became ecologically dominant in the late Oligocene to early Miocene 7-11 million years later (Stromberg 2005). Some C₄ grasses may have originated in the Oligocene, but they became diverse - and made a corresponding contribution to overall vegetation biomass - only in the Miocene (Bouchenak-Khelladi et al. 2009). The spread of grasslands may be associated with a CO₂ decrease perhaps connected with the activities of ectomycorrhizal taxa (Taylor et al. 2009) which made trees less competitive (Pagani et al. 2009). There was a Miocene radiation of grazing mammals (Thomasson & Voorhies 1990) that may be associated with the spread of such prairie and savannah grasses (see also Cerling et al. 1997; Bouchenak-Khelladi et al. 2009) - these mammals had hypsodont dentition, i.e. teeth with high crowns, enamel extending below the gum lines, and short roots to deal with the wear caused by eating the abrasive grasses. C₄ grasses may be less palatable than C₃ grasses, having lower nitrogen content and more sclerenchyma because the veins are closer (see Caswell et al. 1973 in part). However, although prairie grasses expanded in Nebraska in the Early Miocene ca 23 million years before present, hypsodont ungulates were already around by then (Strömberg 2004); Bovidae and Cervidae started diversifying at least 26 million years ago (Bouchenak-Khelladi et al. 2009); massive diversification of ungulates is largely a Miocene phenomenon (Bouchenak-Khelladi et al. 2009). Indeed, in a number of grass groups the density of silica bodies in the leaf epidermis seems to have increased, perhaps as a defence against herbivory (Bouchenak-Khelladi et al. 2009). Cooler temperate grasslands are dominated by the derived Pooideae, all of which are C₃ grasses.

In warmer grasslands C₄ grasses now predominate, and all told C₄ photosynthesis accounts for about 18-21% of terrestrial gross primary productivity (Lloyd & Farquhar 1994; Ehleringer et al. 1997). Over half the taxa with this photosynthetic pathway occur in Poaceae - in total there are some 6,000-6,500 species involved (R. F. Sage, pers. comm.) of which probably somewhat under 4,600 species are grasses (Sage et al. 1999). Although not forgetting the problems over dating just mentioned, the balance of the evidence still suggests that C₄ photosynthesis in grasses seems to have appeared first in the Oligocene, some 32 million years ago as global CO₂ levels in the atmosphere declined (e.g. Christin et al. 2008a; Vicentini et al. 2008; Bouchenak-Khelladi et al. 2009), and is known from grasses from the Early to Middle Miocene in both the Great Plains and Africa, some 25-12.5 million years before present, as C₄ photosynthesis became energetically advantageous in some environments (e.g. Ehleringer 1997 and references; Christin et al. 2008). To emphasize: The great expansion of grasses with C₄ photosynthesis seems to have occured considerably later - i.e. in the late Miocene only 9-4 million years before present - than the initial evolution of this photosynthetic syndrome.

Why C₄ grasses spread in the way they did is still not well understood. Increasing temperature, open habitats, and perhaps especially decreasing precipitation (e.g. Edwards & Still 2007; Edwards et al. 2007; esp. Edwards & Still 2008 - although by no means all C₄ grasses are drought tolerant; Edwards 2009), the high flammability of dry grasses, and windiness are additional factors that would lead to the increased occurence of fires, which would have removed trees from some habitats and hence favoured grasses. Grasses also have dense root masses that would make the establishment of woody vegetation in grassland difficult. Interestingly, both origins of and reversals from C₄ photosynthesis may be clustered (Vicentini et al. 2008, for reversals from C₄, see also Ibrahim et al. 2009). However, which of these or other factors favoured the expansion of grasslands, and what might cause clustering of origins and losses of different photosynthetic mechanisms, is unclear (see also Tipple & Pagani 2007; Christin et al. 2008, for the early origins of of C₄ photosynthesis and its subsequent development; Jacobs et al. 1999 for the paleoecology of Poaceae; Sage & Kubien 2003; Fox & Koch 2004; Osborne & Beerling 2006; Bond 2008; Osborne 2008 for fires, etc.; Osborne & Freckleton 2009: open habitats, then drier conditions). Temperate Pooideae represent a derived clade (Edwards 2009). Much has been written on the evolution of C₄ photosynthesis in grasses, e.g. see Kellogg (1999), Giussani et al. (2001: Paniceae), etc. C₄ photosynthesis may have evolved up to eight times in Panicoideae alone (Giussani et al. 2001); it has also evolved independently in Micrairoideae, Aristidoideae (twice) and Chloridoideae (Kellogg 2000 and references; Christin et al. 2008, 2009a, b; Vicentini et al. 2008; Cerros-Tlatilpa & Columbus 2009 and Christin & Besnard 2009 [both Aristidoideae]). Details of the mechanisms of C₄ photosynthesis and the morphologies associated with it vary considerably in Panicoideae in particular, and taxa like Miscanthus x giganteus carry out this kind of photosynthesis under decidedly cooler conditions than is common (Wang et al. 2008). It has been suggested that the relatively uncommon C₄ PCK subtype (phosphoenolpyruvate carboxykinase) is basal in Chloridoideae, being subsequently lost and reacquired (Christin et al. 2009b). Indeed, the level of parallelisms here may be at the amino acid, similar changes occuring 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 occured in all plants with C₄ photosynthesis (Bläsing et al. 2000).

A perhaps ecologically related feature of a number of grasses scattered in different subfamilies is their accumulation of glycine betaines and other compounds commonly associated with allowing plants containing them to grow in saline conditions (Rhodes & Hanson 1993). As noted above, core Pooideae store carbohydrates as fructans, and this may enable them to survive drought or frost better; fructans are at much lower concentrations elsewhere in the family (Hendry 1993). 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 known from members of Poaceae including both Panicoideae and Pooideae; they confer resistence to fungi, insects, and even herbicides, as well as being allelopathic (Frey et al. 1997, 2009); they are very uncommon in other angiosperms (Schullehner et al. 2008). Sindhu et al. (2008) note that the PACCMAD clade are characterized by a gene that protects the plant against attack by the the ascomycete Cochliobolus carbonorum. Finally, Poaceae, apparently alone in flowering plants, acquire iron through chelation of ferric ions with siderophores which are then taken up by the roots (Schmidt 2003).

Clavicipitaceous endophytes (class 1 endophytes: Rodriguez et al. 2009) are widely distributed among grasses. Leuchtmann (1992) discussed the distribution and host specificity of grass endophytes in general (Clay 1990 is a still useful general review). Some 30% or more of Pooideae are involved in such associations, and both vertical and horizontal transmission of these fungi, of which many (all?) can be placed in ascomycetes-Clavicipitaceae-Balansiae (Clay 1986), occur. This 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), however, the more that is found out about this relationship, the more complex it appears to be. One of the most important endophytes is Epichloë, a systemic (Clavicipitaceae) endophyte restricted to Pooideae; Neotyphodium is its asexual stage, perhaps hybrids of Epichloë (Roberts et al. 2005; Moon et al. 2005): for its phylogeny and evolution see Schardl (1996, 2002), Craven et al. (2001), Clay and Schardl (2002), Jackson (2004 [possible codivergence]), and Gentile et al. (2005). There are four groups of alkaloids that are synthesized by Epichloë: indole diterpenes, lolines, peramine, and the ergot alkaloids (Fleetwood et al. 2007). Hardly surprisingly, the presence of endophytes affects 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, and even the pattern and rate of decomposition of dead grass are also affected (e.g. Madej & Clay 1991 - birds; Omacini et al. 2001 - aphids; Lemmons et al. 2005 - decomposition). Furthermore, the larvae of Phorbia (or Botanophila) flies live on Epichloë stroma, and the adults transmit the spermatia in a fashion analogous to insect pollination of flowers (Bultman 1995), indeed, Epichloë synthesizes compounds that have not been found anywhere else 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). Establishment of the Epichloë/Pooideae relationship may have been involved in the spread of Pooideae from shady to sunny 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). A variety of "grass" alkaloids, including loliine (pyrrolizidine) and ergot alkaloids (ergolines), are in fact synthesized by the fungal member of this association, which could be ca 40 million years old (Schardl et al. 2004). These distinctive loliine alkaloids are primarily active against insects (Schardl et al. 2007; Zhang et al. 2009).

Large numbers of other apparently symptomless endophyte species (class 3 endophytes) may grow together on Poaceae, but little is known about their relationships. Márquez et al. (2007) found 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. For fungal records - very numerous and diverse - on grasses, see Tang et al. (2007); there are at least 1933 species of fungi from bamboos alone. Some root-associated endophytic fungi (class 4) are also coprophilic fungi (Herrera et al. 2009), perhaps aiding in their dispersal.

Poaceae provide food for both adults (as pollen) and larvae (as roots) of Chrysomelidae-Galerucinae-Luperini-Diabrotica beetles (Jolivet & Hawkeswood 1995). Caterpillars of nymphalid butterflies, in particular, the browns, Satyrini, and the related Morphini, are common (over 10% of the records) on grasses; the satyrine group as a whole diverged from other Nymphalidae some 85 million years ago (Wahlberg et al. 2009), the Satyrini themselves diverging from the rest of the group about 65-55 million years ago (Peña & Wahlberg 2008; Wahlberg et al. 2009 - age depends on calibration points used, the position of Satyrini within the satyrine clade differs greatly). Indeed, larvae of Satyrinae-Satyrini, with some 2,200 species, the bulk of the clade, almost exclusively eat grasses, and the main lineages within Satyrini diversified well after the initial divergence of Satyrini only some 36–23 Myr ago - an age perhaps contemporaneous with the spread of grasses (see above: Peña et al. 2006; Peña & Wahlberg 2008, dates from a tree where Satyrini diverge ca 55 million years ago and are not sister to all other Satyrinae). Galling diptera, especially Cecidomyiidae, are quite common here (Labandeira 2005); Cecidomyiid gall midges, notably Mayatiola (M. destructor is the Hessian fly), are quite common on Pooideae in North America (Gagné 1989). Shoot flies (Diptera - Chloropidae) are gall formers on monocots, especially grasses, but they are also simple herbivores and have other life styles (de Bruyn 2005). Chinch bugs of the Hemiptera-Lygaeidae-Blissinae have been most commonly observed on members of the PACCMAD clade, less commonly on the BEP clade; Teracrini are also concentrated on Poaceae (Slater 1976). 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: Dengenhart 2009).

Rusts and smuts are common on Poaceae, and those on Bambusoideae, Pooideae (inc. Stipa and relatives) 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 Pooideae - this species (or complex) infects some 77 genera of mostly pooid grasses (Abbasi et al. 2005 and references).

Poaceae are of course predominantly wind-pollinated with dangling anthers and protandrous flowers. However, insect pollination is known from some forest-dwelling grasses, especially smaller Bambusoideae (Soderstrom & Calderón 1971). Streptochaeta may also be animal pollinated, since it lacks a plumose stigma and the anthers do not dangle; the flowers are protogynous (Sajo et al. 2008). Woody bamboos are known for their synchronized flowering, even when transported thoudands of miles from their native habitat, and many are monocarpic - that is, the plants dies after flowering. Flowering may occur only every 120 years or so, and after a rather protracted period of reproduction, the plant dies. 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. Lodicules, modified members of the inner tepal whorl, seem to be involved in the opening of the staminate or perfect flowers; they can be absent from carpellate flowers (see Sajo et al. 2007; Reinheimer & Kellogg 2009 for references).

The caryopsis is often described as being a distinctive fruit type of the Poaceae; it is basically a variant of an achene. In fact, there is quite a variety of fruit types in the family when it comes to thinking about how dispersal is accomplished (e.g. Werker 1997). Dispersal is quite often by animals, and although few Poaceae have true fruits as dispersal units - an example is Alvimia (Bambusoideae) - there are other structures attracting animals such as elaiosomes (Davidse 1987), as well as hooks and spikes by which the diaspores attach to passing animals (Centotheca is a good example). A number of taxa are wind-dispersed, for example, has long hairs on the awns, while Spinifex and a few other genera are tumbleweeds. Awns can aid in both wind and animal dispersal; the surface microstructure on the awns may result in the achene becoming "planted" in the ground (Elbaum et al. 2007). This is by a principle similar to that which operates when you put an inflorescence of Hordeum up your sleeve; the whole inflorescence migrates up your arm and sometimes also down your back. Davidse (1987) notes a number of taxa with "creeping diaspores" which move along the ground using a similar mechanism.

Relationships within Danthonioideae are complex, and there seems to have been much reticulation in the past (Pirie et al. 2009), as is notoriously the case in Triticeae (G. Petersen et al. 2006a; Mason-Gamer 2008), polyploidy and introgression further complicating the picture.

Malcomber and Kellogg (2005) suggest that there has been duplication of LOFSEP genes within Poaceae, while there has been a duplication of the whole genome in a clade that includes at least Zea, Oryza, Hordeum and Sorghum, and this duplication has been dated to 70-50 million years before present (Schlueter et al. 2004), although diversification of the groups including the cereals seems to have occured ca 20 million years later (Paterson et al. 2004). The duplication of AP1/FUL gene, apparently in stem-group Poaceae, may be involved in the evolution of the spikelet (Preston & Kellogg 2006), and in general, 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). Indeed, 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).

Salse et al. (2008) discuss genome evolution in the family, suggesting that its base chromosome number (x) is 5, the [PACCMAD + BEP] clade at least having a base chromosome number of 12, which is still found in rice (Oryza), for example; however, Hilu (2004) suggested that the base chromosome number for the whole family might be x = 11. One or more rounds of genome duplication has occured, with subsequent reduction in chromosome numbers (Schnable et al. 2009); genome size has varied 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). Overall, there has been very substantial evolution in the genome of grasses, with genome evolution in Triticeae (Pooideae) being particularly accelerated (Luo et al. 2009; see also Messing & Bennetzen 2008; Salse et al. 2009). Indeed, comparisons of expressed sequence tags and general genomes suggest that the genomes of Poaceae are much more different from the genome of Allium (Alliaceae, Asparagales) than is the genome of Arabidopsis (Brassicaceae, Brassicales, rosid II) from that of Allium (Kuhl et al. 2004).

Economic Importance. Wheat (mostly Triticum aestivum - Pooideae), 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). Sorghum and Zea (Panicoideae) and Oryza (Ehrhartoideae) are three other important grain genera. The domestication of maize seems to have occured 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 a phylogeny of Oryzeae, see Guo and Ge (2005), and for information on the complex history of domestication of rice (Oryza spp.) - which occured in two places, at least - see Sweeney and McCouch (2007) and Fuller (2007). 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. The primary cell wall hemicellulose and pectin polysaccharides of grasses are very different from that of other seed plants, both in overall composition and particularities of the composition of the xyloglucans (O'Neill & York 2003); the polysaccharides are less branched than those elsewhere (but overall sampling is very poor). Hatfield et al. (2009) discuss acylation of lignin in grasses.

Anomochlooideae are sometimes described as lacking a ligule (Judziewicz & Clark 2008, which see for other distinctive characters), or the ligule is described as being represented by a ring of hairs... The leaf blades of Neurolepis (Bambusoideae) may be up to 4 m long. The style is hollow in Pharus. In addition, the anther wall consists solely of epidermis and endothecium (i.e. it is of the Reduced type), the latter degenerating before anthesis (Sajo et al. 2007). All in all, Pharus has numerous distinctive features that need to be integrated with the phylogenetic tree; see also Judziewicz and Clark (2008).

A common interpretation of the grass palea, which is often bicarinate, has been that it is prophyllar/bracteolar in nature, monocots commonly having bicarinate prophylls. However, in this scenario bracteoles would probably have 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 will be an apomorphy for all or most of Poaceae. The 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, and Reinheimer & Kellogg 2009 for further details). Given the sister-group relationships between Ecdeicoleaceae and Joinvilleaceae recently found by Marchant and Briggs (2006) and the likelihood that the flowers of Anomochloa are sui generis, the floral morphology of Streptochaeta may be plesiomorphic in the family, or represent an apomorphy for it. Recently 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...). Interestingly, the flowers of Ecdeicolea are also notably monosymmetric, with the two adaxial tepals of the outer whorl larger and keeled, and although this is not directly relevant, comparable differentiation in the outer perianth whorl occurs in Xyridaceae (q.v.); these are all likely to be parallelisms. The tepaloid nature of the lodicules is relatively uncontroversial (see Sajo et al. 2007; Reinheimer & Kellogg 2009 for references).

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, atropous ovules; although both crassi- and tenuinucellate ovules are reported for grasses, Rudall et al. (2005a) suggest that the reports of the former need confirmation. 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 - here the testa and pericarp are fused, basically a variant of an achene. Poaceae are noted for their well developed, lateral embryo with a scutellum - nothing more than a distinctively-shaped haustorial part of the cotyledon that is common in other monocots (= the haustorial cotyledonary hyperphyll if one wants to be technical - see Tillich 2007 for the grass embryo). 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 Andropogonoideae (Diao et al. 2006). Water often congregates in the hollow stems of bamboos, and a distinctive fauna lives there (Kitching 2000).

Some information is taken from Judziewicz and Soderstrom (1989) and in particular from the Grass Phylogeny Working Group (2001); a few small taxa remain unplaced in subfamilies there. For embryo variation, see Reeder (1957), for anatomy, see Metcalfe (1960), for the series of inversions in the single copy region and expansion of the inverted repeats of the chloroplast genome, see Hiratsuka et al. (1989), for C₄ photosynthesis, see also Kellogg (1999), for accD gene loss, see Katayama and Ogihara (1996), for phytoliths and their distribution, see Piperno and Pearsall (1998), Piperno and Sues (2005) and Piperno (2006), 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, and for a summary of genome evolution in the family, see Bennetzen (2007). For the occurence of ergot alkaloids, see Gröger and Floss (1998), for the relationship between genus size, life form and polyploidy, see Hilu (2007a), for inflorescence development, see Malcomber et al. (2006) and Reinheimer et al. (2008: Paniceae), for floral/spikelet evolution, see Whippple and Schmidt (2006), Yuan et al. (2009) and Thompson et al. (2009), for pollen in Chloridoideae, see Liu et al. (2004: not much variation), for cell wall composition, see Fincher (2009), for aerial branching, see Malahy and Doust (2009), and for endosperm development, see Sabelli and Larkins (2009). See Bell and Bryan (2008) for a good general treatment of grass morphology, and for a summary of grass systematics, see Hilu (2007b). Arber (1934) remains the classic account of the family. There is also a useful general bibliography on Poaceae, while Chase (1964) is a classic introduction to the family.

Phylogeny. For overviews of the family, see Soreng and Davis (1998), Kellogg (2000a) and the Grass Phylogeny Working Group (2001); the first in particular show how difficult it is to be sure of the position on the tree of many of the characters mentioned here. Relationships of the major clades within the PACCMAD and BEP clades are for the most part unclear, indeed, the position of Pooideae (Hodkinson et al. 2007, and references; Duvall et al. 2008a) and Ehrhartoideae (Cahoon et al. 2010, as Oryzoideae) are also not clear in some analyses, however, Duvall et al. (2007) found strong support for the BEP clade, albeit the taxon sampling was slight (cf. also Davis & Soreng 2008). In a multi-gene study, Bouchenak-Khelladi et al. (2008) clarified further relationships in the core Poales, while at the same time questioning others. Thus they did not find strong evidence for the monophyly of Anomochlooideae, Streptochaeta possibly being sister to all other Poaceae; Micrairoideae may 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). The relationships obtained by Bouchenak-Khelladi et al. (2009) are largely those in the account above. The BEP clade appeared as paraphyletic and immediately basal to the PACCMAD clade in the analysis of Christin et al. (2008). Leseberg and Duvall (2009) look at platome-level veriation in Poaceae.

For a discussion of the relationships - close, and perhaps even entwined - between Panicoideae and Centothecoideae, see Duvall et al. (2008a) and especially Sánchez-Ken and Clark (2008). Panicoideae have been much studied because of the important crops they contain, e.g. see Giussani et al. (2001). For relationships in the Paniceae, see Zuloaga et al. (2000) and Gómez-Martínez and Culham (2000), 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, which includes Cenchrus, see Donadío et al. (2009), and within Setaria, see Kellogg et al. (2009); see also Sede et al. (2009a) for two new genera and Kellogg (2000c) and Mathews et al. (2002) for the phylogeny of Andropogoneae. For general information on Paniceae, see Crins (1991), for unisexuality, see Le Roux and Kellogg (1999), for inflorescence evolution, see Doust and Kellogg (2002) and Reinheimer and Vegetti (2008), and for the evolution of the NADP-malate dehydrogenase gene following its duplication, see Rondeau et al. (2005). Finally, for more information on relationships within Panicoideae, including those of some of its constituent genera, see papers in Aliso 23: 503-562. 2008.

Relationships within Chloridoideae may be something like [[Neyraudia (panicoid microhairs) + Triraphis] [Eragrostideae [Zoysieae + Cynodonteae (the bulk of the group)]]]] (Peterson et al. 2009). Relationships within Danthonioideae are reticulating (Pirie et al. 2009).

Zhang and Clark (2000) clarified relationships of Bambusoideae, restricting the limits of the subfamily to that now generally accepted; most of the basal grade of Poaceae had been included in bamboos at one time or another. Clark and Triplett (2006) discussed relationships within the Bambusoideae, previously divided into the woody Bambuseae and the herbaceous Olyreae. However, the woody temperate bamboo group may be sister to the rest of the family; the monotypic Buergersiochloa, from New Guinea, is a member of the monophyletic and otherwise entirely New World woody bamboo group, and the Olyreae are derived (e.g. Bouchenak-Khelladi 2008). Sungkaew et al. (2009; five plastid genes) retreived the relationships [Arundinarieae [Olyreae [Neotropical (strictly) Bambuseae + Paleotropical & Austral Bambuseae]]] - and map the distributions of each of these groups. For a phylogeny of the woody bamboos, but with rather little resolution, see Clark et al. (2008), 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 temperate bamboos, see Peng et al. (2008), and of Bambuseae - Arthrostylidiinae, see Tyrell et al. (2009).

Within Ehrhartoideae, the relationships of Oryzeae have been much studied (Guo & Ge 2005; L. Tang et al. 2010 and references); for diversification within Oryza, see Zou et al. (2008). The first seedling leaf of Oryzeae does not have a lamina.

Soreng and Davis (2000) outlined relationships in Pooideae. Within Pooideae, a number of taxa show complex reticulating patterns of relationships; for those in Triticeae in particular, see G. Petersen et al. (2006a) and Mason-Gamer (2008) and references. For a phylogeny of Poeae, which should now include Aveneae, see Quintinar et al. (2007, also Döring et al. 2007; Soreng et al. 2007), for that of Poa, see Gillespie and Soreng (2005) and Gillespie et al. (2009), and for a phylogeny of Stipeae in which Macrochloa may be sister to the rest of the tribe and there are later parallel diversifications in the Old and New Worlds, see Romaschenko et al. (2007, esp. 2008, 2009; Jacobs et al. 2008; Barkworth et al. 2008). Winterfeld (2006) discussed cytogenetic evolution, mainly in the old Aveneae. 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 million years. There are several papers on Poooideae in Aliso 23: 335-471. 2008 which should also be consulted, and see Schneider et al. (2009) for relationships within the whole subfamily, Gillespie et al. (2008) for relationships in Poinae, and Essi et al. (2008) for relationships around Briza.

Classification. For the basic classification of the family, see the Grass Phylogeny Working Group (2001). For generic delimitation in the temperate bamboos, see Peng et al. (2008), and in palaeotropical woody bamboos, see Yang et al. (2008b). Schneider et al. (2009) suggest tribal limits within Pooideae. Hybridisation, introgression, and polyploidy are rife in Pooideae-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. There are also generic problems in Bambuseae - Arthrostylidiinae (Tyrell et al. 2009) and Chusquea must include Neurolepis (Fisher et al. 2009), while Setaria (Panicoideae) will have to be dismembered (Kellogg et al. 2009) and Panicum itself is getting pulverized (e.g. Sede et al. 2008, 2009b). See the World Checklist of Monocots for a checklist of grasses, and for a catalogue of New World Pooideae, see Soreng et al. (2003). Watson and Dallwitz (1992b onwards) includes generic treatments, etc.

Synonymy: Lepturaceae Herter