LIGNOPHYTA

True roots +; lateral meristems: cork cambium producing cork abaxially, vascular cambium producing phloem abaxially and xylem adaxially.

EXTANT SEED PLANTS/SPERMATOPHYTA

Plant woody, evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins derived from (some) sinapyl and particularly coniferyl alcohols, thus containing p-hydroxyphenyl and guaiacyl lignin units, (lignins derived from p-coumaryl alcohol, i.e. S [syringyl] lignin units); true roots present, apex multicellular, xylem exarch, and 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 and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, plastids with starch grains; phloem fibres +; stem cork cambium superficial, root cork cambium deep seated; leaves with single trace from sympodium ["nodes 1:1"]; stomata ?; leaf vascular bundles collateral; leaves megaphyllous [determinancy evolved first, then ad/abaxial symmetry], spiral, simple, lamina with vein density up to 5 mm/mm² [mean for all non-angiosperms 1.8]; axillary buds associated with at most some leaves; prophylls [including bracteoles] two, lateral; 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, developing after pollination, 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 duplications [three - [BP [A/N + C/O]] - copies], nrDNA with 5.8S and 5S rDNA in separate clusters; mitochondrial nad1 intron 2 and coxIIi3 intron and trans-spliced introns present.

MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], S [syringyl] lignin units common, positive Maüle reaction [syringyl:guaiacyl ratio more than 2-2.5:1], and hemicelluloses as xyloglucans; root apical meristem intermediate-open; root vascular tissue oligarch [di- to pentarch], lateral roots arise opposite or immediately to the side of [when diarch] xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, with gelatinous fibres; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, wood parenchyma +; sieve tubes enucleate, sieve plate with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, cytoplasm not occluding pores of sieve plate, companion cells from same mother cell that gave rise to the sieve tube; sugar transport in phloem passive; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves petiolate, lamina [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; most/all leaves with axillary buds; flowers perfect, pedicellate, polysymmetric, parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P not sharply differentiated, with a single trace, outer members not enclosing the rest of the bud, often smaller than inner members; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], ± embedded in the filament, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally 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, 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, stylulus short, hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, dry [not secretory]; ovules few [?1]/carpel, marginal, anatropous, bitegmic, micropyle endostomal, outer integument 2-3 cells across, often largely subdermal in origin, inner integument 2-3 cells across, often dermal in origin, parietal tissue 1-3 cells across [crassinucellate], nucellar cap?; megasporocyte single, hypodermal, megaspore tetrad linear, functional megaspore chalazal, lacking sporopollenin and cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; P deciduous in fruit; seed exotestal; pollen binucleate at dispersal, trinucleate eventually, germinating in less than 3 hours, pollination siphonogamous, tube elongated, growing at 80-600 µm/hour, with pectic outer wall, callose inner wall and callose plugs, growing between cells, penetration of ovules via micropyle [porogamous] within ca 18 hours, distance to first ovule 1.1.-2.1 mm, tube moves between nucellar cells; double fertilisation +, endosperm diploid, cellular [micropylar and chalazal domains develop diffently, first division oblique, micropylar end initially with a single large cell, divisions uniseriate, chalazal cell smaller, divisions in several planes], copious, oily and/or proteinaceous, embryo cellular ab initio, minute; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, ndhB gene 21 codons enlarged at the 5' end, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, paleo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]].

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. This is because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied, there is considerable homoplasy as well as variation within and between families of the ANITA grade 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 as details of sugar transport in the phloem, their placement on the tree is frankly speculative. Finally, for features such as parietal tissue/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), I am unsure where on the tree a thicker nucellus and a stylar epidermal layer are acquired.

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

Phylogeny. For discussion on the relationship of Pandanales, see the Petrosaviales page.

PANDANALES Berchtold & J. Presl   Main Tree, Synapomorphies.

Nucellar cap +; endosperm type?, (reserves starch), embryo minute. - 5 families, 36 genera, 1345 species.

Evolution. Divergence & Distribution. Stem group Pandanales are dated to ca 124 million years before present, crown group Pandanales to ca 114 million years before present (Janssen & Bremer 2004), or the crown group may be as young as ca 50 million years before present (Bremer 2000b); comparable figures in Magallón and Castillo (2009) are ca 134.4 (stem) and 101.4 (crown) and 119.6 (stem) and 102 (crown) million years for relaxed and constrained penalized likelihood datings respectively.

Chemistry, Morphology, etc. Stevenson et al. (2000) suggest other possible characters for the order and groups of families within it. These include a 6 bp deletion in atpA - absent in Talbotia (Velloziaceae), whether or nor it occurs in Barbaceniopsis is unclear (cf. Davis et al. 2004) - and a distinctively connate androecium; tenuinucellate ovules may be another synapomorphy, and starchy endosperm is common in the order. Rudall et al. (2005b) note that floral meristicity, usually not very variable in the monocots, varies considerably in Padanales; floral construction as a whole is rather labile in this order.

Some information on pollen morphology is taken from Grayum (1992); for pollen and tapetum, etc., see Furness and Rudall (2006a).

Phylogeny. This grouping of families is somewhat unexpected. However, Triuridaceae have often been grouped with Pandanales in molecular analyses (Chase et al. 2000a: only 18S rDNA examined) and Graham et al. (2005), but varying in their relationships there. They were found to be sister to Zingiberaceae in some analyses by Davis et al. (2004), but this is an unlikely position, if morphology means anything! Furthermore, Nartheciaceae have sometimes tended to associate with Pandanales, rather than Dioscoreales (q.v. for further details), the clade in which they are included here. Details of the phylogeny of the order are taken from Behnke et al. (2000) and especially Caddick et al. (2002a) and Davis et al. (2004, Fig. 1: in neither were Triuridaceae included). Janssen and Bremer (2003: again, no Triuridaceae) suggest a somewhat different set of relationships. Rudall and Bateman (2006), in a morphological analysis of the order, found another topology, in particular, Triuridaceae were nested within Stemonaceae, but without strong bootstrap support (50³%, hardly the robust placement claimed). There are some morphological characters supporting this position, e.g. the occurrence of thick filaments, free carpels, and pollen morphology.

Includes Cyclanthaceae, Pandanaceae, Stemonaceae, Triuridaceae, Velloziaceae.

Synonymy: Cyclanthales Martius, Roxburghiales Martius, Stemonales Doweld, Triuridales J. D. Hooker, Velloziales Reveal

VELLOZIACEAE J. Agardh, nom. cons.   Back to Pandanales

Xeromorphic; vessel elements in roots often with simple perforation plates, vessels also in stem and leaf [?ref.]; phloem in at least smaller bundles in two abaxial-lateral strands; sieve tube plastids in the stem 1³ µm across; cortex in three zones; stomata brachyparacytic; leaves persistent; flowers violet, large; A borne in mouth of "hypanthium", anthers bisporangiate/monothecal; pollen bi- or trinucleate; ovary inferior, placentae bifid, stalked-capitate, style long; ovules many/carpel, parietal tissue absent; capsule loculicidal; endosperm with starch.

5[list]/240. South America and Africa-Madagascar to Arabia, China.

1. Acanthochlamydoideae P. C. Kao

Caespitose rhizomatous herb; steroidal saponins +?; root stele tetrarch, pith absent; lateral roots arise opposite xylem poles; cauline vascular tissue aggregated in the centre of the stem; vessels also in stem and leaf, elements with simple perforation plates; scape with a root-like vascular cylinder; raphides and tannin cells 0; palisade tissue 0; midrib with back-to-back vascular bundles; leaves spiral, ligule basal, surrounding stem; inflorescence scapose, compound capitate, leaf adnate to scape; T ca 1/2 connate; anthers short, filaments short; septal nectaries 0; "seed coat" ca 2 cells across, walls ± lignified, testa cells ± elongated, tegmen tanniniferous; embryo large/medium; n = 19; seedling?

1/1: Acanthochlamys bracteata. S.E. Tibet and S.W. China (Map above: see Ying et al. 1993 - green). [Photo - Flower] [Photo - Fruit]

Synonymy: Acanthochlamydaceae P. C. Kao

2. Vellozioideae Rendle

Woody or herbaceous, adventitious roots often growing down through persistent leaf bases; biflavonoids + [Xerophyta]; (velamen +); (vessels not in stem and leaf; perforations scalariform); sieve tube plastids with angular crystals and other loosely-packed crystals; transfusion tracheids in leaf bundles, phloem in two abaxial-lateral strands; (raphides/styloids +); stomata in grooves, (on both surfaces), (cuticular waxes as aggregated rodlets), leaves with marginal bundles and transfusion tissue; indumentum various; leaves (spirally)3-ranked, conduplicate-flat, midrib +, margins usu. spiny; inflorescences often single-flowered, bracteoles lateral; hypanthium +/0; median T in outer whorl adaxial [e.g. Barbacenia], T largely free; (corona +, usu. adnate to adaxial A); (A not adnate to T), (dithecal; with 3 or 6 fascicles [A in fascicle connate], development within fascicles ± centripetal), filaments cylindrical, anthers long; (pollen in tetrads); septal nectaries +, stigmas large, erect or spreading, capitate; micropyle bi(endo)stomal, endothelium and funicular obturator +, suprachalazal tissue massive; fruit also poricidal or with intercostal apertures; testa ± tanniniferous, exotesta thickened or not, exotegmen, layered-thickened, tanniniferous; endosperm helobial, cells elongated, wall formation in small chalazal chamber precedes that in large micropylar chamber, embryo medium to short; n = 7, 8, 17, 24 [x = 12?]; collar rhizoids +.

4/240: Vellozia (105), Barbacenia (90). South America and Africa-Madagascar (to Arabia) (Map above: see Ayensu 1973b - red). [Photo - Habit, Flower.]

Synonymy: Barbaceniaceae Arnott

• Velloziaceae are xeromorphic and sometimes tree-like monocots (but the "trunk" is made up largely of adventitious roots) that may be recognised by their usually 3-ranked leaves with persistent bases and spiny margins. The inflorescences are terminal, although often appearing axillary, and often have one flower. The flowers are rather large, with violet petaloid tepals and a long style; there may be a corona, and the stamens can be many.

Evolution. Divergence & Distribution. Stem group Velloziaceae are dated to ca 108 million years before present, crown group Velloziaceae (Acanthochlamys was not included) to ca a mere 14 million years before present (Janssen & Bremer 2004: note topology, Velloziaceae and Stemonaceae are sister taxa). Mello-Silva et al. (2011) interpret the split of Acanthochlamys from the rest of the family in terms of a drift-induced vicariant event.

Ecology & Physiology. Velloziaceae include many dessication-tolerant and arborescent taxa (see Naidoo et al. 2009 for Xerophyta viscosa, also analysis of substances secreted on adaxial surface of the leaf). The true stem is small, and soon rots away, the trunk being made up both of adventitious roots, each initially with a velamen, and of persistent leaf bases (Porembski 2006).

Chemistry, Morphology, etc. The anatomty of the stem/rhizome of Acanthostachys is unclear; it seems to consist of perhaps four vascular bundles in the centre, almost touching, and apparently with a small amount of non-vascular tissue in the middle (Kao ). The leaves of Acanthochlamys have a rather large basal adaxial ligule ensheathing the stem; the other genera have sheathing bases. Phloem in the "midrib" bundles of the leaves is sometimes arcuate, but in smaller bundles in particular it is broken up into two abaxial-lateral strands (Smith & Ayensu 1976). Amaral and Mello-Silva (2005, esp. 2008) suggest that the tetracytic stomata described from the Vellozioideae are more correctly to be thought of as paracytic. What is described here as the hypanthium in Velloziaceae may bear the same indumentum as occurs on the petiole; assuming the traditional interpretation of hypanthium, the perianth members must be considered to be usually more or less free. Even so, the stamens may be adnate to the tepals for most of their length, as in Barbaceniopsis. The corona develops late, and although partly associated with the bases of the filaments, its vasculature is in part tepalline (Sajo et al. 2010, which see also for androecial development).

The roots of Acanthochlamys are tetrach or triarch and lack pith, and so are unlike the roots of most other monocots. The remarkable anatomy of the scape of that genus has been described as "similar to that of a leaf ensheathing a rhizome" (Kao & Kubitzki 1998: 56), although the central part of the stem is more like a root, not a rhizome. The anthers opposite the inner tepal members are inserted higher up on the tube than the anthers opposite the outer members.

Information is taken from Ayensu (1973a: general), Smith and Ayensu (1976: monograph - with anatomy - of New World taxa), de Menezes (1980: androecial evolution), Williams et al. (1991: chemistry), Kubitzki (1998b: general), Kao and Kubitzki (1998: Acanthochlamydaceae, much detail), Behnke et al. (2000: general), Strassburg and de Menezes (2001: development) and Kao (1989) and Gao (2012: also reprints of some earlier papers) - Kao and Gao are one and the same...

Phylogeny. Talbotia (African) is mesophytic and its filaments are not adnate to the perianth. It is perhaps sister to the other Vellozioideae (but cf. Behnke et al. 2000), however, basal relationships are unresolved. Barbacenia is paraphyletic, but Barbacenioideae are monophyletic (corona +; n = 7). Vellozioideae sensu Menezes are paraphyletic (Salatino et al. 2001), however, there is in general considerable disagreement between the topologies implicit in different morphology-based classifications of the family (Mello-Silva 2005), and that in Mello-Silva is only partly congruent with that of the molecular tree of Behnke et al. (2000). Nevertheless, Acanthochalmys is clearly sister to the rest of the family (Behnke et al. 2000; Mello-Silva 2005). In a joint molecular and morphological study, Mello-Silva et al. (2011) found relationships [Acanthochlamys [Xerophyta (inc. Talbotia) + the rest (support not strong)]], and suggest a number of apomorphies for the main clades, although optimisation of some of them is difficult.

Classification. Acanthochalmys is sister to the rest of the family and is morphologically and anatomically rather different from them, but subfamilial status is appropriate (Behnke et al. 2000; Mello-Silva 2005; cf. Gao 2012). For suggestions as to generic limits in the family, see Mello-Silva et al. (2011).

[Triuridaceae, Stemonaceae [Pandanaceae + Cyclanthaceae]]: septal nectaries 0.

TRIURIDACEAE Gardner, nom. cons.   Back to Pandanales

Plant herbaceous, echlorophyllous, myco-heterotrophic; chemistry?; root hairs 0-many; vessels 0; root stele solid; stem with vascular bundles in a single ring, (endodermis +); crystals 0; plant glabrous; cuticular waxes as parallel series of platelets, within a series transversely arranged; stomata 0; leaves spiral, reduced, (base sheathing; closed); inflorescence racemose, bracteole 0; T valvate, with a single trace [Kupea]; A connate or not, filaments stout; tapetum cells uninuclear; pollen trinucleate, inaperturate, surface gemmate, gemmae with protruberances or spines; G 10-many, plicate, styles solid, no transmitting tissue, stigma penicillate to smooth, ?dry; ovules basal, parietal tissue absent, nucellar cap 0, endothelium, hypostase +; seeds endotestal, cuticle below very thick, exotesta persisting; endosperm hemicellulosic, copious, almost a chalazal haustorium; n = 9, 11, 12(-16); seedling?

11[list]/50. Pantropical (map: from van de Meerendonk 1984; Maas & Rübsamen 1986; Rübsamen-Weustenfeld 1991).

1. Sciaphileae Miers

Plant monoecious, (flowers perfect); T 4, 6, 8, (basally connate), apex acute, with a tuft of hairs or not; A 2, 3, 4, 6, anthers opening diagonally-transversely (vertically), tapetum plasmodial; pollen (monosulcate - Sciaphila), 24-40 µm across; style gynobasic; ovule 1/carpel; fruit a follicle; seed with testal cells on chalazal side collapsed, or small, thickish walled, over rest of seed endotestal cells large and radially elongated, wall thickenings radial.

5/40: Sciaphila (30). Mostly Old World, esp. Indo Malesia and the Pacific, few New World. [Photo - Sciaphila].

2. Triurideae Miers

Root hairs few to none; plant usually dioecious; T 3, 6, apex caudate, (connate basally); staminate flowers: A 3, 6, anther dehiscence longitudinal, pollen 15-21 µm across; pistillate flowers: carpel development centrifugal [Triuris], style (sub)terminal; ovule 1/carpel; embryo sac tetrasporic, the three chalazal megaspores fuse, divide twice, 7-celled and 8-nucleate, the antipodals triploid {Fritillaria-type]; fruit an achene; endotestal cells with wall thickenings parallel to long axis of seed; endosperm pentaploid, when young with starch.

4/7. American Tropics. [Photo - Triuris.]

3. Kupeaeae Cheek

Root hairs none; inflorescence a spike; plant dioecious; T 4, apex acute; staminate flowers: (bract adnate to flower - Kupea), flower monosymmetric; (T basally connate); A 4, anther dehiscence transverse, pollen ca 25 µm across; pistillate flower: style (sub)terminal; ovules 2/carpel, hemitropous to campytotropous; fruit indehiscent.

2/3. Africa; Cameroon and Tanzania.

• Triuridaceae are mostly rather small echlorophyllous myco-heterotrophic plants; they have racemose or spicate inflorescences with small flowers that have pointed tepals and many separate carpels; the latter often have a decidedly irregular surface in fruit.

Evolution. Divergence & Distribution. Despite the delicate nature of plants of this family, fossil flowers of Triuridaceae (two genera) are known from ca 90 million years before present in New Jersey (Gandolfo et al. 1998a, 2002). Until recently they were the earliest monocot fossils known, but that honour has now been taken by Araceae (see Friis et al. 2004), and the exact identity of these fossils is questionable (Friis et al. 2011).

Rübsamen-Weustenfeld (1991) lists other characters especially of endosperm and embryo size and seed anatomy that separate Sciaphileae and Triuridae; some may turn out to be apomorphies, but they are not known for Kupeaeae.

Floral Biology. Lacandonia schismatica has stamens borne inside the carpels, unique in angiosperms, but the origin of this odd morphology is unclear. Although it has been suggested that these "flowers" may be pseudanthia (Rudall 2003), recent work by Ambrose et al. (2006) suggests that heterotopy is a more likely explanation.

Lacandonia can self pollinate: Pollen grains germinate while still in the anther and the tubes grow through the tissue of the flower to the ovule (Márquez-Guzmán et al. 1989). In general, polllination by small flies is likely (Rudall & Bateman 2006).

Chemistry, Morphology, etc. mycorrhizae are of the Paris type (Imhoff 1998). The roots lack pith (von Guttenberg 1968) and the root stele is monarch or diarch - the entire stele from the endodermis inwards may be lignified (Johow 1889 and references).

Although the flowers of Triuridaceae are tiny, staminate flowers of Kupea and Kihansia are quite strongly monosymmetric (Cheek 2003a; Rudall et al. 2007b). Staminate and carpellate flowers usually lack rudiments of pistils and stamens respectively. Inter- and intraspecific ariation in the number of parts of the flower is considerable (see Rübsamen-Weustenfeld 1991; Maas-van der Kamer 1995; Rudall et al. 2007b). In the perfect flowers of Lacandonia and carpellate flowers of Triuris individual carpel primordia develop from compound primordia, and in the former stamen and carpel primordia develop from a common precursor. Rudall (2008) suggests that the basic construction of the gynoecium in at least some Triuridaceae is fasciculate, the fascicles being radially elongated, but there seems to be considerable variation in gynoecial development (see also Rübsamen-Weustenfeld 1991). The strong asymmetry of the seeds, apparently restricted to some Sciaphileae (e.g. Wirz 1910, but cf. Batygina et al. 1990 - but interpretation of sections entails knowing in what plane they were cut...), means that they are more or less winged on one side.

For ovule and seed, see Johow (1889 and references) and Wirz (1910), for floral development and a lot more, see Rübsamen-Weustenfeld (1991, see also Maas-van der Kamer 1995) and Rudall (2003b), for carpels, etc., Igersheim et al. (2001), for pollen, etc., Furness et al. (2002a), and for general information, Maas-van der Kamer and Weustenfeld (1998) and Cheek (2003a).

Phylogeny. Rudall and Bateman (2006) found that morphological analyses suggested that Kupea (Kihansia was not studied) was sister to the rest of the family and Sciaphileae were paraphyletic. Recognition of Lacandonia as a genus may make Triuris paraphyletic (Vergara-Silva et al. 2003); if this relationship is confirmed, the phylogenetic context for any evolutionary explanation of the distinctive floral construction of Lacandonia becomes very specific indeed.

Classification. For tribes, I follow Rübsamen-Weustenfeld (1991) and Cheek (2003a); the latter described external morphology only for Kupeaeae.

Previous Relationships. Triuridaceae have often been associated with Alismataceae and relatives, all having separate carpels and so assumed to be primitive.

Synonymy: Lacandoniaceae E. Martínes & Ramos

[Stemonaceae [Pandanaceae + Cyclanthaceae]]: (styloids +); flowers other than 3-merous; placentation parietal, style 0.

STEMONACEAE Caruel, nom. cons.   Back to Pandanales

(Plant tuberous), with scale leaves, stem erect (twining); (unspecified saponins - Stemona), alkaloids with pyrrolo- or pyrido(1,2,-alpha)- azepine nucleus, +; stem vascular bundles in 1 or 2 rings, those of inner or only ring amphivasal; vessel elements with scalariform perforation plates also in stem; petiole bundles in arc; (styloids +); hairs 0; leaves two-ranked or opposite, petiolate, not sheathing, midrib simple (not distinct), cross veins fine, well developed, scale leaves sheathing; inflorescences axillary, cymose or flowers single; (flower monosymmetric - Croomia heterosepala), pedicel articulated; T 4(-5), perianth tube short; A adnate to base of T, 4(-5), ± connate, connective expanded; G 1 to [3], (inferior), placentae apical or basal, style branches ± separate; ovules 2 to many/carpel, outer integument to 5 cellls across, inner integument to 3 cells across, parietal tissue (0?-2) cells across; fruit a capsule [?type]; seeds ridged, aril of uniseriate or vesicular hairs from hilum, raphe or micropyle; testa multipicative, several-layered, ridges many cells high, tanniniferous, inner 4 layers thick-walled, (tegmen persists, cell walls thickened); endosperm copious, ?starch, walls not pitted; n = 7, 9, 12; seedling with non-photosynthetic cotyledon, primary root well developed.

4[list]/27. China and Japan to Australia, S.E. U. S. A. (Croomia ) (map: from Duyfjes 1993; Fl. N. Am. 26: 2002). [Croomia - Habit].

• Stemonaceae can be recognised by their elegant leaves with a petiole, sometimes a distinct midrib, and very close to distant longitudinal veins; there are conspicuous cross veins. When dry, the leaves are often very thin. The inflorescences are axillary and the flowers are 4- or 5-merous.

Evolution. Divergence & Distribution. Stem group Stemonaceae are dated to ca 108 million years before present, crown group Stemonaceae to ca 84 million years before present (Janssen & Bremer 2004).

Floral Biology & Seed Dispersal. At least some Stemonaceae are pollen flowers (Vogel 1981).

Myrmecochory is common in seeds of the family (Lengyel et al. 2010).

Chemistry, Morphology, etc. The distinctive alkaloids found in Stemonaceae with their pyrrolo- or pyrido(1,2,-alpha) azepine nucleus (see also Pilli & Ferreira de Oliveira 2000) are probably an apomorphy of the family. Duyfjes (1992) inadvertently suggested that Stemonaceae s. str. - i.e. not including Pentastemona - lack scale leaves. These are well documented on the underground parts (e.g. Tomlinson & Ayensu 1968), while van Steenis (1982) noted that they were sheathing and compared this feature to the sheathing photosynthetic leaves of Pentastemona, suggesting an equivalence; Stemona, etc., do not have sheathing leaves.

The morphology of the inflorescence and the nature of the breeding system of Pentastemona need more study - also its anatomy, chemistry, etc. Stemona phyllantha has epiphyllous inflorescences. Note that the anatomy of the seed ridges varies considerably.

Additional information is taken from Tomlinson and Ayensu (1968: Croomia), van Steenis (1982: Pentastemona), Duyfjes (1991: general), Swamy (1964b) and Bouman and Devente (1992), both ovules and seeds, Kubitzki (1998b: general), Furness and Rudall (2000b: pollen aperture number) and Rudall et al. (2005b: floral morphology).

Phylogeny. Pentastemona appears to be well embedded within the family (e.g. Jiang et al. 2006, molecular data, but cf. Rudall & Bateman 2006, morphological analysis); on balance, its distinctive features are likely to be derived.

• Pentastemona can be briefly characterised as follows: Succulent monopodial herb; scale leaves 0; hairs uniseriate; stem and petiole vascular bundles?; stomata para- or tetracytic; leaves spiral, with compound midrib, sheath ?closed; inflorescences (branched) racemose; flowers 5-merous, perianth tube long to short; A 5, connate into a fleshy ring, basally adnate to T and connectives apically adnate to stigmas, pollen inaperturate, atectate; [G 3], inferior, placentation parietal, many ovules/carpel, stigmatic lobes well developed; fruit a berry; seed arillate; sarcoexotesta +, endotesta with massive U-shaped thickenings, producing ridges; seedling?

Synonymy: Croomiaceae Nakai, Pentastemonaceae Duyfjes, Roxburghiaceae Wallich

[Pandanaceae + Cyclanthaceae]: stem vascular bundles compound; styloids +; stomata tetracytic, subsidiary cells with oblique cell divisions; leaves ± plicate-appearing when mature; inflorescence bracts conspicuous, inflorescence a dense spike or head, flowers sessile [a spadix]; flowers imperfect; staminate flowers: stamens usu. several-many; pollen porate; pistillode +; carpellate flowers: staminodes +; ovules apotropous, with radiating subepidermal nucellar/chalazal cells; fruit an indehiscent syncarp [baccate or drupaceous]; endotesta well developed, internally to that are two persistent cuticular layers; cotyledon not photosynthetic, seedling with all internodes ± elongated.

Evolution. Divergence & Distribution. The divergence between the two families has been dated to ca 98 million years before present (Janssen & Bremer 2004).

Chemistry, Morphology, etc. The compound vascular bundles can sometimes be seen under a hand lens; the vascular bundles have groups of vessels at opposite ends with smaller cells in between. There are vessels in the leaves in Pandanaceae, but not in Cyclanthaceae.

Phylogeny. A close relationship between this pair of families in consistently obtained in molecular studies and also has strong morphological support.

Previous relationships. A group recognised in the past was the Spadiciflorae; this included those taxa with a spadix and often also a spathe, i.e. Pandanaceae, Cyclanthaceae, Araceae and Arecaceae. These families are now placed in three orders, Pandanales, Alismatales and Arecales.

PANDANACEAE R. Brown, nom. cons.   Back to Pandanales

Plant woody, trees or shrubs, or climbers with roots from leaf axils, not rhizomatous; vessels elements also in stem and leaf, perforation plates scalariform; sieve tube plastids also with peripheral fibres; (leaf wax platelets aggregated); leaves spirally three- or four-ranked, conduplicate-flat, M-shaped when mature, spiny, (sheaths closed; base auriculate - Freycinetia); plant di-(mon)oecious; (inflorescence paniculate - Sararanga), inflorescence bracts usually colored; P connate as cupule [Sararanga] to 0; staminate flowers: A 2-many, variously aggregated [on underside of peltate structure]; pollen exine three-layered [level?]; (pistillode 0); carpellate flowers: (staminodes 0); G 1-several, free to connate, intra-ovarian trichomes +; ovules (1/carpel - Freycinetia), apotropous, (micropyle bistomal), parietal tissue 1-5 cells across, (nucellar cap ca 2 cells across), obturator and hypostase +; embryo sac (bisporic - Pandanus), incorporating nucellar cells at chalazal end; fruit baccate or drupaceous; seed coat thin, (testa ca 5 layers thick, exotesta developed - Sararanga); (endosperm starchy); n = 25, 28, 30; hypocotyl long [Freycinetia], primary root branched [Pandanus].

4[list]/885: Pandanus (700), Freycinetia (180). W. Africa to the Pacific (map: see Heywood (1978: Africa); Callmander et al. 2003). [Photos - Staminate Flower, Carpellate Flower.]

• Pandanaceae are woody plants with long, spiny-toothed leaves that are curved-flat in bud; the inflorescence is terminal and usually (elongated-)capitate and the perianth is at most vestigial.

Evolution. Divergence & Distribution. Crown group Pandanaceae began to diverge ca 51 million years before present (Janssen & Bremer 2004). The pollen genus Pandaniidites is known from North America where it spans the Cretaceous-Tertiary boundary; it has been found in rocks up to 70 million years old (Hotton et al. 1994). This perhaps suggests that the climate in those localities must have been tropical, however, it has since been shown that Pandaniidites is associated with flowers of Limnobiophyllum, to be assigned to Araceae-Lemnoideae (Stockey et al. 1997; Stockey 2006)!

Chemistry, Morphology, etc. Since there is no perianth, the position of the ovary is often difficult to ascertain, but it is clearly superior in some Freycinetia (e.g. Huynh 1991). The carpels vary from free to variously connate and fasciate, and their orientation varies from centripetal to centrifugal (cf. Cercidiphyllum!), sometimes within a single floral unit (Stone 1968). The embryo sac of Pandanus appears to have extra antipodal cells, however, these come from the nucellus (see Maheshwari 1955 for discussion).

Information, including testa anatomy, is taken from Fagerlind (1940a: Pandanus seems not always to have a bisporic embryo sac), Strömberg (1956), and Cheah and Stone (1975), all embryology, Zimmermann et al. (1974: vascular organization in the stem), Dahlgren et al. (1985: general), Hotton et al. (1994: pollen), Stevenson and Loconte (1995: phylogeny), Cox et al. (1995: phylogeny), Stone et al. (1998; general), and Huynh (2001: Sararanga).

Phylogeny. For the phylogeny of the family, see Callmander et al. (2003); major relationships within it were poorly resolved.

Classification. Callmander et al. (2003) divide Pandanus, but relationships of the segregated genus are unclear.

Synonymy: Freycinetiaceae Le Maout & Decaisne

CYCLANTHACEAE A. Richard, nom. cons.   Back to Pandanales

Large herbs; vascular tracheids or vessels in root and leaf; petiole bundles scattered; (mucilage cells +); leaves spirally two-ranked, petiolate, vernation plicate or variants, often divided deeply, sheath?; plant monoecious; inflorescence branched, spadiciform, inflorescence bracts [spathe] colored or not; carpellate flowers: ovules (epitropous), micropyle bistomal, parietal tissue absent, outer integument 3-5 cells across, nucellar cap 2-3 cells across, (hypostase +); (postament +); endosperm helobial, embryo short; seeds with palisade endotesta; collar rhizoids +.

12/225: Central and tropical South America (map: from Harling 1958; fossil Cyclanthus [blue] from Smith et al. 2009).[List]

Cyclanthoideae

Subepidermal sclereids +; non-articulated laticifers +; lysigenous air spaces with transverse septae +; leaves modified plicate, 2-costate; inflorescence with whorls of staminate and carpellate "flowers"; P 0; staminate flowers: A in 4 rows per whorl, connate basally; carpellate flowers: G with ovary cavity with closely-set placentae; ovules lacking nucellar cap, funicles long; fruit dry, syncarpous, carpellary annulus sliding off the inflorescence axis and splitting down the middle; seeds ridged, embedded in mucilage; endotestal cells palisade, inner periclinal walls granular; n = 9.

1/1: Cyclanthus bipartitus. Central and N. South America, the Lesser Antilles. [Photo - Flower.]

Carludovicioideae

Many epiphytes, (climbers); cork subepidermal or outer cortical; (styloids +); leaves (two-ranked), 1- or 3-costate; inflorescences (axillary), flowers in spirals; staminate flowers: P in one (two) whorls, 6+ (-30), with abaxial gland (none); A ca 10-many, filaments swollen basally; carpellate flowers: 4(-8)-merous; staminodes opposite P, long-filiform; G 4, ± inferior, alternating with P, (placentae apical); ovules many/carpel; fruit baccate, syncarpous or not, apically circumscissile or with other unusual methods of opening; (seeds exotegmic); (endosperm starchy); n = 9, 15, 16.

11/225: Asplundia (100), Dicranopygium (50), Sphaeradenia (50). Central and tropical South America, the Greater Antilles. [Photo - Flower, Fruit.]

• Cyclanthaceae are more or less herbaceous and have large, petiolate, plicate, toothed and/or deeply-divided leaves. The inflorescence is spadiciform and the flowers have a more or less inferior ovary. Cyclanthus itself can be recognised by its bifid leaves (or there is a bifid midrib) and distinctive spadix with spirally-arranged flowers. Although Cyclanthaceae can be confused with palms, their petioles are usually notably softer than those of palms and may be rounded.

Evolution. Divergence & Distribution. Crown group Cyclanthaceae may begin to diverge ca 77 million years before present (Janssen & Bremer 2004). Interestingly, Cyclanthus has quite recently been identified from the European Eocene (seeds had previously been misidentified as a Scirpus), where it may even be a diagnostic element of the vegetation - along with Nypa (Smith et al. 2008). This changes how one thinks of the evolution and distribution of the family.

Floral Biology & Seed Dispersal. Carludovicia is associated with derelomine flower weevils the adults of which pollinate the flowers while the larvae eat the developing seeds (Franz 2004). Indeed, weevils are commonly associated with cyclanthaceous inflorescences, and their larvae may eat the gynoecia (Harling 1958).

The fruits of Carludovicioideae are baccate, syncarpous or not, and are apically circumscissile or have other unusual methods of opening. For example, the subfleshy infructescences of genera like Carludovica open irregularly from the apex as the outer part of the infructescence recurves and pulls away, exposing the brightly-coloured interior. Dispersal is by animals.

Chemistry, Morphology, etc. In staminate flowers, both perianth and stamen number may increase. There is considerable variation in pollen morphology and seed morphology and anatomy; Furness and Rudall (2006) suggest that the pollen grains of Cyclanthaceae, alone in the order, lack endexine lamellae.

For information on morphology and vernation of leaves, see Wilder (1981a, b), for embryology, see Harling (1946), for growth habit, see Wilder (1992), for seeds, see Smith et al. (2008), and for much information on just about everything, see Harling (1958) and Harling et al. (1998).

Phylogeny. For a detailed morphological phylogeny of the family, see Eriksson (1994).