EMBRYOPSIDA Pirani & Prado
Gametophyte dominant, independent, multicellular, not motile, initially ±globular; showing gravitropism; acquisition of phenylalanine lysase [PAL], microbial terpene synthase-like genes +, triterpenoids produced by CYP716 enzymes, phenylpropanoid metabolism [lignans +, flavonoids + (absorbtion of UV radiation)], xyloglucans in primary cell wall, side chains charged; plant poikilohydrous [protoplasm dessication tolerant], ectohydrous [free water outside plant physiologically important]; thalloid, leafy, with single-celled apical meristem, tissues little differentiated, rhizoids +, unicellular; chloroplasts several per cell, pyrenoids 0; glycolate metabolism in leaf peroxisomes [glyoxysomes]; centrioles/centrosomes in vegetative cells 0, microtubules with γ-tubulin along their lengths [?here], interphase microtubules form hoop-like system; metaphase spindle anastral, predictive preprophase band + [with microtubules and F-actin; where new cell wall will form], phragmoplast + [cell wall deposition centrifugal, from around the anaphase spindle], plasmodesmata +; antheridia and archegonia jacketed, surficial; blepharoplast +, centrioles develop de novo, bicentriole pair coaxial, separate at midpoint, centrioles rotate, associated with basal bodies of cilia, multilayered structure + [4 layers: L1, L4, tubules; L2, L3, short vertical lamellae] (0), spline + [tubules from L1 encircling spermatid], basal body 200-250 nm long, associated with amorphous electron-dense material, microtubules in basal end lacking symmetry, stellate array of filaments in transition zone extended, axonemal cap 0 [microtubules disorganized at apex of cilium]; male gametes [spermatozoids] with a left-handed coil, cilia 2, lateral; oogamy; sporophyte multicellular, cuticle +, plane of first cell division transverse [with respect to long axis of archegonium/embryo sac], sporangium and upper part of seta developing from epibasal cell [towards the archegonial neck, exoscopic], with at least transient apical cell [?level], initially surrounded by and dependent on gametophyte, placental transfer cells +, in both sporophyte and gametophyte, wall ingrowths develop early; suspensor/foot +, cells at foot tip somewhat haustorial; sporangium +, single, terminal, dehiscence longitudinal; meiosis sporic, monoplastidic, MTOC [MTOC = microtubule organizing centre] associated with plastid, sporocytes 4-lobed, cytokinesis simultaneous, preceding nuclear division, quadripolar microtubule system +; wall development both centripetal and centrifugal, 1000 spores/sporangium, sporopollenin in the spore wall laid down in association with trilamellar layers [white-line centred lamellae; tripartite lamellae]; nuclear genome size [1C] <1.4 pg, main telomere sequence motif TTTAGGG, LEAFY and KNOX1 and KNOX2 genes present, ethylene involved in cell elongation; chloroplast genome with close association between trnLUAA and trnFGAA genes [precursors for starch synthesis], tufA gene moved to nucleus; mitochondrial trnS(gcu) and trnN(guu) genes +.
Many of the bolded characters in the characterization above are apomorphies of subsets of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se.
All groups below are crown groups, nearly all are extant. Characters mentioned are those of the immediate common ancestor of the group,  contains explanatory material, () features common in clade, exact status unclear.
Abscisic acid, L- and D-methionine distinguished metabolically; pro- and metaphase spindles acentric; sporophyte with polar transport of auxins, class 1 KNOX genes expressed in sporangium alone; sporangium wall 4≤ cells across [≡ eusporangium], tapetum +, secreting sporopollenin, which obscures outer white-line centred lamellae, columella +, developing from endothecial cells; stomata +, on sporangium, anomocytic, cell lineage that produces them with symmetric divisions [perigenous]; underlying similarities in the development of conducting tissue and of rhizoids/root hairs; spores trilete; shoot meristem patterning gene families expressed; MIKC, MI*K*C* genes, post-transcriptional editing of chloroplast genes; gain of three group II mitochondrial introns, mitochondrial trnS(gcu) and trnN(guu) genes 0.
[Anthocerophyta + Polysporangiophyta]: gametophyte leafless; archegonia embedded/sunken [only neck protruding]; sporophyte long-lived, chlorophyllous; cell walls with xylans.
Sporophyte well developed, branched, branching apical, dichotomous, potentially indeterminate; hydroids +; stomata on stem; sporangia several, terminal; spore walls not multilamellate [?here].
Vascular tissue + [tracheids, walls with bars of secondary thickening]; stomata involved in gas exchange.
EXTANT TRACHEOPHYTA / VASCULAR PLANTS
Sporophyte with photosynthetic red light response, stomata open in response to blue light; plant homoiohydrous [water content of protoplasm relatively stable]; control of leaf hydration passive; plant endohydrous [physiologically important free water inside plant]; (condensed or nonhydrolyzable tannins/proanthocyanidins +); xyloglucans with side chains uncharged [?level], in secondary walls of vascular and mechanical tissue; lignins +; stem apex multicellular, with cytohistochemical zonation, plasmodesmata formation based on cell lineage; vascular development acropetal, tracheids +, in both protoxylem and metaxylem, G- and S-types; sieve cells + [nucleus degenerating]; endodermis +; leaves/sporophylls spirally arranged, blades with mean venation density ca 1.8 mm/mm2 [to 5 mm/mm2], all epidermal cells with chloroplasts; sporangia adaxial, columella 0; tapetum glandular; ?position of transfer cells; MTOCs not associated with plastids, basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; suspensor +, shoot apex developing away from micropyle/archegonial neck [from hypobasal cell, endoscopic], root lateral with respect to the longitudinal axis of the embryo [plant homorhizic].[MONILOPHYTA + LIGNOPHYTA]
Sporophyte endomycorrhizal [with Glomeromycota]; growth ± monopodial, branching spiral; roots +, endogenous, positively geotropic, root hairs and root cap +, protoxylem exarch, lateral roots +, endogenous; G-type tracheids +, with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangium dehiscence by a single longitudinal slit; cells polyplastidic, MTOCs diffuse, perinuclear, migratory; blepharoplasts +, paired, with electron-dense material, centrioles on periphery, male gametes multiciliate; chloroplast long single copy ca 30kb inversion [from psbM to ycf2]; mitochondrion with loss of 4 genes, absence of numerous group II introns; LITTLE ZIPPER proteins.
Sporophyte woody; stem branching lateral, meristems axillary; lateral root origin from the pericycle; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].
Plants heterosporous; megasporangium surrounded by cupule [i.e. = unitegmic ovule, cupule = integument]; pollen lands on ovule; megaspore germination endosporic [female gametophyte initially retained on the plant].
EXTANT SEED PLANTS / SPERMATOPHYTA
Plant evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); microbial terpene synthase-like genes 0; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignin chains started by monolignol dimerization [resinols common], particularly with guaiacyl and p-hydroxyphenyl [G + H] units [sinapyl units uncommon, no Maüle reaction]; root stele diarch to pentarch, xylem and phloem originating on alternating radii, cork cambium deep seated; stem apical meristem complex [with quiescent centre, etc.], plasmodesma density in SAM 1.6-6.2[mean]/μm2 [interface-specific plasmodesmatal network]; eustele +, protoxylem endarch, endodermis 0; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, sieve tube plastids with starch grains; phloem fibres +; cork cambium superficial; leaf nodes 1:1, a single trace leaving the vascular sympodium; leaf vascular bundles amphicribral; guard cells the only epidermal cells with chloroplasts, stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; axillary buds +, exogenous; prophylls two, lateral; leaves with petiole and lamina, development basipetal, lamina simple; sporangia borne on sporophylls; spores not dormant; microsporophylls aggregated in indeterminate cones/strobili; grains monosulcate, aperture in ana- position [distal], primexine + [involved in exine pattern formation with deposition of sporopollenin from tapetum there], exine and intine homogeneous, exine alveolar/honeycomb; ovules with parietal tissue [= crassinucellate], megaspore tetrad linear, functional megaspore single, chalazal, sporopollenin 0; gametophyte ± wholly dependent on sporophyte, development initially endosporic [apical cell 0, rhizoids 0, etc.]; male gametophyte with tube developing from distal end of grain, male gametes two, developing after pollination, with cell walls; female gametophyte initially syncytial, walls then surrounding individual nuclei; embryo cellular ab initio, suspensor short-minute, embryonic axis straight [shoot and root at opposite ends; plant allorhizic], cotyledons 2; embryo ± dormant; chloroplast ycf2 gene in inverted repeat, trans splicing of five mitochondrial group II introns, rpl6 gene absent; whole nuclear genome duplication [ζ - zeta - duplication], two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], 5.8S and 5S rDNA in separate clusters.
ANGIOSPERMAE / MAGNOLIOPHYTA
Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANA grade?], lignin also with syringyl units common [G + S lignin, positive Maüle reaction - syringyl:guaiacyl ratio more than 2-2.5:1], hemicelluloses as xyloglucans; root cap meristem closed (open); pith relatively inconspicuous, lateral roots initiated immediately to the side of [when diarch] or opposite xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0, hypodermis suberised and with Casparian strip [= exodermis]; shoot apex with tunica-corpus construction, tunica 2-layered; 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, not occluding pores of plate, companion cell and sieve tube from same mother cell; ?phloem loading/sugar transport; nodes 1:?; dark reversal Pfr → Pr; protoplasm dessication tolerant [plant poikilohydric]; stomata brachyparacytic [ends of subsidiary cells level with ends of pore], outer stomatal ledges producing vestibule, reduction in stomatal conductance with increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, secondary veins pinnate, fine venation hierarchical-reticulate, (1.7-)4.1(-5.7) mm/mm2, vein endings free; flowers perfect, pedicellate, ± haplomorphic, protogynous; parts free, numbers variable, development centripetal; P +, ?insertion, members each with a single trace, outer members not sharply differentiated from the others, not enclosing the floral bud; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], each theca dehiscing longitudinally by a common slit, ± embedded in the filament, walls with at least outer secondary parietal cells dividing, endothecium +, cells elongated at right angles to long axis of anther; tapetal cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine lamellate only in the apertural regions, thin, compact, intine in apertural areas thick, pollenkitt +; nectary 0; carpels present, superior, free, several, ascidiate [postgenital occlusion by secretion], stylulus at most short [shorter than ovary], hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, dry; suprastylar extragynoecial compitum +; 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, nucellar cap?; megasporocyte single, hypodermal, functional megaspore lacking cuticle; female gametophyte lacking chlorophyll, not photosynthesising, four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; ovule not increasing in size between pollination and fertilization; pollen grains land on stigma, bicellular at dispersal, mature male gametophyte tricellular, germinating in less than 3 hours, pollen tube elongated, unbranched, growing towards the ovule, between cells, growth rate (20-)80-20,000 µm/hour, apex of pectins, wall with callose, lumen with callose plugs, penetration of ovules via micropyle [porogamous], whole process takes ca 18 hours, distance to first ovule 1.1-2.1 mm; male gametes lacking cell walls, ciliae 0, siphonogamy; double fertilization +, ovules aborting unless fertilized; P deciduous in fruit; mature seed much larger than fertilized ovule, small [<5 mm long], dry [no sarcotesta], exotestal; endosperm +, cellular, development heteropolar [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 short [<¼ length of seed]; plastid and mitochondrial transmission maternal; Arabidopsis-type telomeres [(TTTAGGG)n]; nuclear genome size [1C] <1.4 pg [mean 1C = 18.1 pg, 1 pg = 109 base pairs], whole nuclear genome duplication [ε/epsilon event]; 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, palaeo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]]; chloroplast chlB, -L, -N, trnP-GGG genes 0.
[NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]]: wood fibres +; axial parenchyma diffuse or diffuse-in-aggregates; pollen monosulcate [anasulcate], tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.
[AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: phloem loading passive, via symplast, plasmodesmata numerous; vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood + [reaction wood: with gelatinous fibres, G-fibres, on adaxial side of branch/stem junction]; tectum reticulate; anther wall with outer secondary parietal cell layer dividing; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.
[[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]] / MESANGIOSPERMAE: benzylisoquinoline alkaloids +; sesquiterpene synthase subfamily a [TPS-a] [?level], polyacetate derived anthraquinones + [?level]; outer epidermal walls of root elongation zone with cellulose fibrils oriented transverse to root axis; P more or less whorled, 3-merous [?here]; pollen tube growth intra-gynoecial; extragynoecial compitum 0; carpels plicate [?here]; embryo sac bipolar, 8 nucleate, antipodal cells persisting; endosperm triploid.
[MONOCOTS [CERATOPHYLLALES + EUDICOTS]]: (extra-floral nectaries +); (veins in lamina often 7-17 mm/mm2 or more [mean for eudicots 8.0]); (stamens opposite [two whorls of] P); (pollen tube growth fast).
MONOCOTYLEDONS / MONOCOTYLEDONEAE / LILIANAE Takhtajan
Plant herbaceous, perennial, rhizomatous, growth sympodial; non-hydrolyzable tannins [(ent-)epicatechin-4] +, neolignans 0, CYP716 trterpenoid enzymes 0, benzylisoquinoline alkaloids 0, hemicelluloses as xylan; root epidermis developed from outer layer of cortex; endodermal cells with U-shaped thickenings; cork cambium [uncommon] superficial; stele oligo- to polyarch, medullated [with prominent pith], lateral roots arise opposite phloem poles; stem primary thickening meristem +; vascular development bidirectional, bundles scattered, (amphivasal), vascular cambium 0 [bundles closed]; tension wood 0; vessel elements in roots with scalariform and/or simple perforations; tracheids only in stems and leaves; sieve tube plastids with cuneate protein crystals alone; stomata parallel to the long axis of the leaf, in lines; prophyll single, adaxial; leaf blade linear, main venation parallel, the veins joining successively from the outside at the apex and forming a fimbrial vein, transverse veinlets +, unbranched [leaf blade characters: ?level], vein/veinlet endings not free, margins entire, Vorläuferspitze +, base broad, ensheathing the stem, sheath open, petiole 0; inflorescence terminal, racemose; flowers 3-merous [6-radiate to the pollinator], polysymmetric, pentacyclic; P = T, each with three traces, median T of outer whorl abaxial, aestivation open, members of whorls alternating, [pseudomonocyclic, each T member forming a sector of any tube]; stamens = and opposite each T member [primordia often associated, and/or A vascularized from tepal trace], anther and filament more or less sharply distinguished, anthers subbasifixed, wall with two secondary parietal cell layers, inner producing the middle layer [monocot type]; pollen reticulations coarse in the middle, finer at ends of grain, infratectal layer granular; G , with congenital intercarpellary fusion, opposite outer tepals [thus median member abaxial], placentation axile; compitum +; ovule with outer integument often largely dermal in origin, parietal tissue 1 cell across; antipodal cells persistent, proliferating; fruit a loculicidal capsule; seed small to medium sized [mean = 1.5 mg], testal; embryo long, cylindrical, cotyledon 1, apparently terminal [i.e. bend in embryo axis], with a closed sheath, unifacial [hyperphyllar], both assimilating and haustorial, plumule apparently lateral; primary root unbranched, not very well developed, stem-borne roots numerous, hypocotyl short, (collar rhizoids +); no dark reversion Pfr → Pr; duplication producing monocot LOFSEP and FUL3 genes [latter duplication of AP1/FUL gene], PHYE gene lost.
[ALISMATALES [PETROSAVIALES [[DIOSCOREALES + PANDANALES] [LILIALES [ASPARAGALES + COMMELINIDS]]]]]: ethereal oils 0; (trichoblasts in vertical files, proximal cell smaller); raphides + (druses 0); leaf blade vernation supervolute-curved or variants, (margins with teeth, teeth spiny); endothecium develops directly from undivided outer secondary parietal cells; tectum reticulate with finer sculpture at the ends of the grain, endexine 0; (septal nectaries +) [intercarpellary fusion postgenital].
[PETROSAVIALES [[DIOSCOREALES + PANDANALES] [LILIALES [ASPARAGALES + COMMELINIDS]]]]: cyanogenic glycosides uncommon; starch grains simple, amylophobic; leaf blade developing basipetally from hyperphyll/hypophyll junction; epidermis with bulliform cells [?level]; stomata anomocytic, (cuticular waxes as parallel platelets); colleters 0.
[[DIOSCOREALES + PANDANALES] [LILIALES [ASPARAGALES + COMMELINIDS]]]: nucellar cap 0; endosperm nuclear [but variation in most orders].
[LILIALES [ASPARAGALES + COMMELINIDS]]: (inflorescence branches cymose); protandry common.
[ASPARAGALES + COMMELINIDS]: style long; whole nuclear genome duplication [τ/tau event].
COMMELINIDS: Unlignified cell walls with ferulic acid ester-linked to xylans [fluorescing blue under UV, green with NH3], flavonolignins + [resinols ± 0]; exodermal cells monomorphic; (vessels in stem and leaves); SiO2 bodies +, in leaf bundle sheaths; stomata para- or tetracytic, (cuticular waxes as aggregated rodlets [looking like a scallop of butter]); inflorescence branches determinate, peduncle bracteate; P = K + C, bicyclic [stamens adnate to/inside corolla/inner whorl only]; pollen starchy; embryo short, broad.
[POALES [COMMELINALES + ZINGIBERALES]]: primary and secondary cell walls mostly with (glucurono)arabinoxylans; stomata subsidiary cells with parallel cell divisions; endosperm reserves starchy.
[COMMELINALES + ZINGIBERALES]: rhizodermal cells dimorphic; inflorescences with many-flowered cincinnal branches [helicoid cymes]; P = T; A opposite T; tapetum invasive or amoeboid. Back to Main Tree
Age. Divergence of the two clades dates to ca 114 m.y. (Janssen & Bremer 2004), while the figures in Wikström et al. (2001) are (85-)81, 73(-69) m.y., and in Bremer (2000b) ca 84 m.y.; Magallón and Castillo (2009) estimated ca 109.7 and 99.9 m.y. while Bell et al. (2010) offer the figures of (101-)88, 86 m. years. However, Kress and Specht (2005) thought stem-group Zingiberales might be 158 m.y.o. (but ages of 124-122 m.y. are given by Kress & Specht 2006), while estimates are (107-)101, 99(-94) m.y. in Hertweck et al. (2015), (112-)97.5(-82) m.y. in Givnish et al. (2016b), (114-)92(-83) m.y. in Merckx et al. (2008a), 85-83 m.y. and 82-72 m.y. in Mennes et al. (2013, 2015 respectively), about 79.8 m.y.a. in Magallón et al. (2015), and a mere 52.4 m.y. in Naumann et al. (2013).
Evolution: Divergence & Distribution. Monosymmetric flowers in this clade, especially in Zingiberales and Haemodoraceae, have a variety of very different morphologies; for different types of monosymmetry, see Rudall and Bateman (2004). Monosymmetric flowers can be optimised to this node, as by Endress (2011a), who suggested that it might be a key innovation here, interestingly, monosymmetry in Commelinaceae, at least, is associated with the abaxial/ventral expression of the CYC gene (Bartlett & Specht 2011; Preston & Hileman 2012; Hileman 2014), i.e. a position inverse to that in Lamiales in particular, and the floral orientation of monocots in general is inverted. However, many monosymmetric monocot flowers are upside down... A change from a biseriate perianth (K + C) to a biseriate tepaloid perianth, with the stamens individually opposite each tepal, can also be placed at this node, which then has consequences for floral evolution in Zingiberales (c.f. Barrett et al. 2013, but see Sass et al. 2016). Enantiostyly is common in this clade.
Chemistry, Morphology, etc. Tapetal variation in those few Zingiberales studied is extensive (Prakash et al. 2000; Furness & Rudall 2001; Simão et al. 2007).
Phylogeny. For further discussion of the relationships of the [Commelinales + Zingiberales] clade, see the Arecales page.
COMMELINALES Dumortier Main Tree.
Mycorrhizae absent; (phenyphenalenones +); vessel elements with scalariform perforation plates; cuticle waxes not as aggregated rodlets; (flower enantiostylous); seed coat testal and tegmic; endosperm abundant, helobial, cell wall formation in small chalazal chamber precedes that in large micropylar chamber; collar rhizoids +. - 5 families, 68 genera, 812 species.
Age. Crown-group Commelinales are dated to ca 110 m.y.a. (Janssen & Bremer 2004: c.f. topology), about 101 m.y. by Tank et al. (2015: Table S2), (108.4-)95.9(-83.2 m.y. by Eguchi and Tamura (2016), ca 90.2 m.y. by Tang et al. (2016), (103.5-)80.5(-57.5) m.y. by Givnish et al. (2016b), (104-)75(-50) m.y. by Merckx et al. (2008a), (75-)71, 66(-62) m.y. by Wikström et al. (2001), about 68.5 m.y. by Magallón et al. (2015), while Bell et al. (2010) suggest an age of (91-)76, 70(-55) m.y., Hertweck et al. (2015) (101-)95, 90(-87) m.y., and Mennes et al. (2013, see also 2015) 84-47 m. years.
Note: Boldface denotes possible apomorphies, (....) denotes a feature common in the clade, exact status uncertain, [....] includes explanatory material. Note that the particular node to which many characters, particularly the more cryptic ones, should be assigned is unclear. This is partly because homoplasy is very common, in addition, basic information for all too many characters is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there are the not-so-trivial issues of how character states are delimited and ancestral states are reconstructed (see above).
Evolution. Genes & Genomes. There has been a reduction in the GC content of the genome in this clade (Smarda et al. 2014).
There is a five base pair insertion in the matK gene in members of Hanguanaceae and Pontederiaceae (Tamura et al. 2004a) and it was absent in Haemodoraceae, but no other taxa were sampled.
Chemistry, Morphology, etc. For phenyphenalenones, see Otálvaro et al. (2002).
Tapetal raphides are known from Commelinaceae, Philydraceae and Haemodoraceae, but their general distribution is unclear (Hardy & Stevenson 2000; Prychid et al. 2003a); there may be systematically interesting variation in the pattern of endothecial thickenings (Manning 1996). For monosymmetry, see Rudall and Bateman (2004).
Phylogeny. For relationships, see Hopper et al. (1999), S. W. Graham et al. (2006), Chase et al. (2006) and Saarela et al. (2008). Graham (in Graham et al. 2002) noted that there was very strong support for the grouping [Haemodoraceae + Pontederiaceae]. Janssen and Bremer (2004) suggest a rather different - and perhaps unlikely - set of relationships - [Philydraceae [Hanguanaceae [Haemodoraceae [Commelinaceae + Pontederiaceae]]]]; Givnish et al. (2006b: ndhF gene only) also found Philydraceae to be sister to other Commelinales, but the position had little support (and see also Hertweck et al. 2015), while Davis et al. (2004; see also Chase et al. 2000) found a clade [Hanguanaceae [Commelinaceae + Pontederiaceae]]. Relationshps in Z.-D. Chen et al. (2016) are [Philydraceae [Commelinaceae + Pontederiaceae]].
There has been much discussion over the position of Hanguanaceae in particular, which in morphological analyses tends to cluster - sometimes quite strongly (Rudall et al. 1999) - with Zingiberales, although it lacks the inferior ovary of members of that order. Molecular analyses suggest the inclusion of Hanguanaceae in Commelinales, and Givnish et al. (1999: rbcL analysis) suggested that Hanguanaceae were sister to Commelinaceae (see also Tillich 1997).
Includes Commelinaceae, Haemodoraceae, Hanguanaceae, Philydraceae, Pontederiaceae.
Synonymy: Haemodorales Martius, Hanguanales Reveal, Philydrales Dumortier, Pontederiales Martius
[Hanguanaceae + Commelinaceae]: stem above ground; embryo small; cotyledon not photosynthetic.
HANGUANACEAE Airy Shaw Back to Commelinales
Mucilage canals +; hairs multicellular, branched; epicuticular waxes 0; leaves spiral, with petiole and blade; plant dioecious; inflorescence branched-spicate, flowers sessile; T small; staminate flowers: filaments broadened and connate at very base; ?tapetum; pollen inaperturate, exine spinulose; pistillode +; carpellate flowers: base of inner staminodes ± surrounded with scale-like structure [esp. adaxial; ?nectar-secreting]; G with intra-ovarian trichomes, mucilage-producing, style ± 0, stigmas 3; ovule 1/carpel, basal, straight, micropyle?, parietal tissue none, epidermal cells anticlinally elongated, suprachalazal zone massive; fruit a 1-seeded berry; seed bowl-shaped [placenta inside the bowl!]; testa ca 5 cells across, endotesta with inner periclinal walls thickened, tegmen with two layers of crossing fibres; endosperm type?; n = ca 24, 36, 45, chromosomes 1> µm long; primary root well developed.
1 [list]/14(-?50). Sri Lanka, South East Asia to Palau and N. Australia (map: see Hewson 1986). [Photo - Fruit]
Chemistry, Morphology, etc. Raphides may occur, but they are rare (Prychid & Rudall 1999). In Takhtajan (1985) there are illustrations of a several-layered testa and a massively-thickened tegmen with crossing fibres. However, Tillich (1996b) described the seed coat as being testal - but his outer layer seems comparable to Takhtajan's endotesta and his inner layer to one of the tegmic layers.
Additional information is taken from Bayer et al. (1998b), Tillich and Sill (1999), and Rudall et al. (1999), all general; also Leong-Skornicková and Boyce (2015: carpellate flowers) and Tillich (1996b: seedling).
Previous Relationships. Hanguana was often included in ciliariaceae (now in Poales), Cronquist (1981) included them in his broadly-circumscribed Liliales, while more recent morphological studies have linked them with Zingiberales (see above).
COMMELINACEAE Mirbel, nom. cons. Back to Commelinales
6-hydroxyflavonoids +; vessels also in stem; raphide canals; hairs uniseriate; stem with swollen nodes; (prophylls lateral); leaves spiral (two-ranked), midrib prominent, sheath closed, Vorläuferspitze 0 [?level]; andromonoecy common; inflorescences axillary (terminal), (boat-like bracts conspicuous); flowers open one day; K + C, C deliquescent; (G ), septal nectaries 0; micropyle (exo)/endostomal, (nucellus apex exposed), outer integument 3-7(-10) cells across, inner ca 2 cells across, parietal tissue 0, or 1-2 cells across, nucellar cap to 2 cells across; fruit a loculicidal capsule, endocarp with fibres in vertical series, transversely elongated, variously thickened; (seeds uniseriate); exotesta thin, endotesta silicified, operculum + ["embryotega"]; endosperm nuclear, chalazal haustorium +, cotyledon ± lateral, suspensor 0; n = 4³; coleoptile +.
40 [list]/652. Tropical and temperate.[Photos - Collection.]
Age. Stem group Commelinaceae are dated to ca 89 m.y. (Janssen & Bremer 2004: c.f. topology).
1. Cartonematoideae G. C. Tucker
Annual, ?caespitose perennial [bulbous]); SiO2 bodies 0; stem collenchyma 0; raphide canals next to veins or 0; stomata paracytic or tetracytic; glandular microhairs 0, although plant glandular pubescent; leaves long-linear; (inflorescence spicate), (leaf opposed, cymose); flowers ± sessile, median K adaxial [?Triceratella], C yellow; ?tapetum; ovule ?straight; operculum lacking collar, most of testa sloughed off; embryo undifferentiated; seedling collar short, mesocotyl +, primary root strong; n = 12.
2/12. Australasian, Triceratella (to be included?) Zimbabwe (map: from FloraBase ix.2010; Trop. Afr. Fl. Pl. Ecol. Distr. 7. 2012).
Synonymy: Cartonemataceae Pichon, nom. cons.
2. Commelinoideae Eaton
Rather succulent herbs, (annual); (mycorrhizae 0); cyanidin 3,7,3'-triglucoside +; (velamen +); stem collenchyma +; vessel elements with simple perforation plates, also in stem and leaf; stem with narrow cortex and endodermis-like sheath enclosing vascular bundles that connect only at the nodes; (SiO2 bodies +); raphide canals between veins; stomata tetracytic, etc.; 3-celled glandular microhairs +; (leaf blade vernation involute); (inflorescence axillary), (prophyll lateral); flowers with the median sepal adaxial, (obliquely monosymmetric [when monosymmetric, C often 2, adaxial members]), (enantiostylous); (T), 1- or 3- trace, blue, pink or white (yellow), (C tubular); A 1-6, (adnate to C), heteranthy common, anthers poricidal, with 2+ fibrous middle layers, (connective [much] expanded), filaments often with dense uniseriate hairs, staminodes often 2-4, attractive; tapetal cells with druses; pollen with raphides; ovules >1/carpel, straight to campylotropous; (embryo sac bi- or tetrasporic, 8[haploid]-nucleate), (antipodal cells ± persisting - Tinantia), polar nuclei fuse early; (fruit a berry), (endocarp with cross-shaped - Forrestia); seed endotestal, (also exotegmic), operculum testal, with a micropylar collar; starch grains complex; n =4<, often "large".
38/640: Commelina (170), Tradescantia (70), Aneilema (68), Murdannia (50), Cyanotis (50). Tropical, also temperate, not Europe (map: see Heywood 1978; modified from Fl. N. Am. 22: 2000; FloraBase 2004; Trop. Afr. Fl. Pl. Ecol. Distr. 7. 2012). [Photo - Flower, another Flower.]
Age. Crown-group Commelinoideae are dated to ca 62 m.y. (Janssen & Bremer 2004).
Synonymy: Ephemeraceae Batsch, nom. rej., Tradescantiaceae Salisbury
Evolution. Pollination and Seed Dispersal. For the evolution of breeding systems in Tradescantieae, see Hertweck and Pires (2004). Indehiscent geocarpic fruits are produced by Commelina bengalensis and Tapheocarpa.
Genes & Genomes. Over 1/4 of Commelinaceae examied have B chromos0omes (Melianthaceae have more, see Weiss-Schneeweiss & Schneeweiss 2013).
Chemistry, Morphology, etc. Remizowa et al. (2011) suggested that the apparently cymose part inflorescences of Tradescantia were in fact racemose, but c.f. e.g. Panigo et al. (2011). On the other hand, the apparently racemose inflorescences of Cartonema have been described as having one flower/cincinnus (Brenan 1966). Leaf-opposed inflorescences and axillary inflorescences that perforate the leaf sheath as they emerge (as in Buforestia) are known from the family.
Floral symmetry and construction are variable. Flowers may be monosymmetric by the corolla, one petal being much reduced in Commelina, or primarily by the androecium, and the expression of monosymmetry may change during the development of the flower (Hardy et al. 2004). In Dichorisandra the bracteoles are more or less lateral and the plane of symmetry of the flower is transverse, while in other taxa it is oblique (e.g. Eichler 1875); Preston and Hileman (2012) show most flowers of Commelinoideae as having an inverted orientation, and this is compatible with Eichler's suggestion. Interestingly, TB1-like genes, involved in the development of monosymmetry elsewhere in monocots and eudicots, are not expresssed in the sepal-like abaxial inner petal of Commelina communis, although they are in the other petals, stamens and staminodes; there is a similar pattern of expression of B-class DEF-like genes, not being expressed in the abaxial member of the petal whorl either (Preston & Hileman 2012). Cochliostemon has asymmetric flowers (Hardy & Stevenson 2000a for development). Enantiostyly occurs, but is uncommon. For expression (very little) of B-class genes (DEF) in the sepals of species that have them see Ochiai et al. (2004). Flowers may have tepals, the stamens then being opposite each tepal member, or a calyx and corolla; the inner T/corolla members may have only a single trace. A floral tube may be formed by connation of the petals, as in Weldenia, or by adnation of alternating corolla and the filaments of the antisepalous stamens (Rohweder 1979b). Variation in androecial development is extreme, and in some taxa androecial development has been reported as being centrifugal, perhaps a variant of obdiplostemony (Hardy & Stevenson 2000b; Hardy & Ryndock 2012, but see Endress 2010d).
Mabberley (1987) suggested that some taxa may have a small second cotyledon, but to what structure this might refer is unclear. Tillich (1996a [check]) described the cotyledon as being of the dropper type. Seedling leaves and often those at the base of axillary shoots are often two-ranked even in those taxa that have spiral leaves predominating in the vegetative plant.
Some information is taken from Rohweder (1963, 1970b), Faden and Hunt (1991), and Faden (1998), all general, Calderón et al. (2009: ecdysteroids), Stirton and Harborne (1980: anthocyanins - see cyanidin 3,7,3'-triglucoside distribution, Cartonematoideae not sampled), Martínez and Swain (1985: flavonoids), Tomlinson (1966: anatomy), Evans et al. (2000: stomatal development), Choob and Mavrodiev (2001: prophylls, etc), Hofreiter and Tillich (2002: root anatomy, quite a bit of variation), Burns et al. (2008: vegetative morphology), Hardy et al. (2000b, 2004: floral development), Tischler (1915: tapetal development), and Maheshwari and Baldev (1959) and Chikkmannaiah (1963 and references), both embryology, and Jones and Jopling (1972: cytology).
Phylogeny. A morphological phylogeny shows little resolution, although anatomical characters gave significantly more support for a rbcL phylogeny than did other kinds of characters (Evans et al. 2000, c.f. Evans et al. 2003). In morphological studies, most taxa with strongly monosymmetric flowers form a clade; Triceratella is widely separated from Cartonema, but the latter is sister to the rest of the family. Givnish (2003, summary tree only, no support values) emphasized that morphological data did not retrieve a monophyletic Commelineae and Tradescantieae largely because of high homoplasy of androecial characters, while molecular (rbcL) data did find these tribes to be monophyletic (with the exception of Floscopa, see below; Calisia [Tradescantieae] had a similarly isolated position in the morphological analyses). Evans et al. (2003: rbcL phylogeny, Triceratella not studied) also note conflict between morphology and molecules.
Within Commelinoideae, Commelineae and Tradescantieae are monophyletic, with Floscopa (chromosomes 3³ µm long), previously included in Tradescantieae, as sister to both (Givnish 2003). Commelineae have stomata with 6 subsidiary cells, spiny pollen and chromosomes ca 1-5 µm long; monosymmetric flowers are commonest here and stamen hairs, if present, are not moniliform. Tradescantieae have stomata with 2-6 subsidiary cells, moniliform stamen hairs and chromosomes ca 2-10 µm long (c.f. Judd et al. 2002); flowers with tepals (i.e. not differentiated into sepals and petals) are commonest in this clade. Wade et al. (2006) carried out a two-gene analysis of Tradescantieae; the position of Palisota is still unresolved. Burns et al. (2011), in an extensive analysis of Commelinoideae (no Cartonematoideae included), found Commelineae and Tradescantieae to be moderately supported, with Palisota and Spatholirion successive sister taxa to Commelineae (moderate support). Callisia (Tradescantieae) is paraphyletic, Gibasis is polyphyletic (Hertweck & Pires 2004). Spalink et al. (2009) outlined relationships in Aneilema.
Classification. Wade et al. (2006) provide a subtribal classification of Tradescantieae; some subtribes are paraphyletic; generic limits in Tradescantieae will have to be adjusted (see Hertweck & Pires 2004).
[Philydraceae [Haemodoraceae + Pontederiaceae]]: SiO2 bodies 0; styloids +; T with tannin cells; sclereids in placentae; T persistent in fruit.
Age. The age of this clade is about 62.3 m.y. (Magallón et al. 2015).
PHILYDRACEAE Link, nom. cons. Back to Commelinales
Proanthocyanins +; stem vascular tissue various; (stomata tetracytic); hairs often wooly; leaves two-ranked, ventralized isobifacial [oriented edge on to the stem] or terete [Philydrella]; groups of flowers [?arrangement] in axils of spathe-like bracts; flowers open for one day, enantiostylous; T whorls differentiated, both petal-like, 2 adaxial outer T plus adaxial inner T all fused, abaxial outer T, large, free, inner T 2, lateral, small, adnate to A (not - Helmholtzia); A 1, [median member of outer whorl], (anther curved or coiled), (filament winged); tapetum glandular, cells 2-4-nucleate; pollen with raphides, (in tetrads); septal nectaries 0, (style impressed), stigma large; ovules many/carpel, outer integument 1-2 cells across, inner integument 2-3 cells across, (parietal tissue 2 cells across), ± postament, hyopostase, funicular obturator +; (seed with caruncle [from outer integument] and chalazal processes); exotesta with thick cellulose walls, (cells spiralling around seed), endotegmen tanniniferous, operculum tegmic; endosperm also with oil and crystalline aleurone bodies, chalazal haustorium +, chalazal chamber cellular ab initio, embryo long, suspensor hardly developed; n = 8, 16, 17; cotyledon linear, bifacial.
4 [list]/5. Australia (all genera) to Southeast Asia (map: from Fl. Austral. 25. 1987; Hamann 1998b).
Age. Crown group Philydraceae are dated to (37-)33(-29) m.y. by Wikström et al. (2001) and ca 47 m.y. by Janssen and Bremer (2004).
Evolution: Divergence & Distribution. Philydrum languinosum is found throughout most of the range of the family; all other species have local distributions in New Guinea and Australia.
Chemistry, Morphology, etc. Information is taken from Malmanche (1919: anatomy), Kapil and Walia (1965: embryology of Philydrum), Tillich (1994: seedlings), Hamann (1962b: endosperm, 1966: much detail, 1998: general) and Adams (1987: general).
Phylogeny. For phylogenetic relationships within Philydraceae, see Saarela et al. (2008); Philydrella is sister to the rest of the family.
[Haemodoraceae + Pontederiaceae]: phenylphenalenones +; endothecial cells with base-plates; ektexine not tectate or columellate.
Age. Magallón et al. (2015) suggested that this clade is around 44.4 m.y. old.
Chemistry, Morphology, etc. For phenylphenalenones, see Otálvaro et al. (2002); these are phytoalexins with the formula (phenylphenalenone) of C19 H12 O, three six-C rings fused plus a benzene.
For the base plates of endothecial cells, see Manning (1996: not in Commelinaceae, other families unknown, sampling poor).
HAEMODORACEAE R. Brown, nom. cons. Back to Commelinales
(Plant cormose); fructans, chelidonic acid, flavones +; vessel elements in roots often with simple perforation plates, (vessels also in stem and leaf); leaves two-ranked, isobifacial [oriented edge on to the stem], (margins [minutely] spiny); cyme bifurcated (not); prophyll ± lateral; flowers (large), (monosymmetric), plane of symmetry transverse to oblique; T connate to free; A (connective appendages +); pollen with raphides; exine (1-)2(-3)-layered [no foot layer]; ovary inferior, placentae swollen; ovules 1-many/carpel, micropyle (exo)/endostomal, parietal tissue to 3 cells across, (nucellar cap +); cells of testa (and tegmen) variously elongated, ± thin-walled, operculum 0; chalazal endosperm haustorium +, embryo small/minute; ?collar rhizoids.
13 [list]/116 - two subfamilies below. Tropics and warm temperate regions.
Age. Divergence within the crown group Haemodoraceae began ca 81 m.y. (Janssen & Bremer 2004).
1. Haemodoroideae Arnott
(Plant bulbous); roots red, cortical cells radially aligned (4-)8-12-layered; tannin containing cells 0; (bulliform cells +); hairs with distinctive basal cells; flowers enantiostylous, tannin cells 0; T (densely hairy inside - Lophiola); A 3, opposite inner P, (1 - Pyrorrhiza), (staminodes +); ovary superior (inferior), (nectary 0); seeds often flattened or marginally winged, pubescent or not; cotyledon not photosynthetic, hypocotyl at most short; n = 12, 15, 19-21.
8/39: Haemodorum (20). Tropics and warm temperate regions, rather scattered, in Africa, only southern (map: from Heywood 1978 [Africa]; Australia's Virtual Herbarium i.2014; Maas & Maas-van der Kamer 1993; Fl. N. Am. 26: 2002). [Photo - Flower, Fruit, Flower]
Age. The start of divergence within Haemodoroideae has been put at the early Eocene ca 47.9 m.y.a. (Hopper et al. 2009).
Synonymy: Dilatridaceae M. Roemer, Wachendorfiaceae Herbert, Xiphidiaceae Dumortier
2. Conostylidoideae Lindley
Root (stele 2-arch - Tribonanthes), vessels scattered throughout the pith, cortical cells 10-20-layered, endodermal cells usu. rectangular/radially elongated, outer tangential wall relatively thin; tannin-containing cells; SiO2 sand +; (epidermal walls thickened), hairs branched; (inflorescence capitate); flowers ± pubescent outside (and inside), (monosymmetric); T (valvate); (A adnate to T), (with ± petal-like dorsal appendage); pollen 2-8 porate; ovary at least partly inferior; (fruit indehiscent or a schizocarp); (seeds ridged, tegmen massive - Anigozanthus); cotyledon photosynthetic, hypocotyl +, primary root well developed; n = 4-8, 11.
5/80: Conostylis (50). S.W. Australia (map: from Fl. Austral. 45. 1987). [Photo - Flower]
Age. Divergence within Conostyloideae began in the Eocene ca 42 m.y.a. (Hopper et al. 2009).
Synonymy: Conostylidaceae Takhtajan
Evolution: Divergence & Distribution. The restriction of Conostylidoideae to S.W. Australia is remarkable given that it is not exactly a young clade; Hopper et al. (2006, 2009) discuss the diversification of this group, in particular, that of Conostylis.
Aerne-Hains and Simpson (2016) put variation in anatomical features in the family in a phylogenetic context (see also Simpson et al. 2006).
Plant-Animal Interactions. Bugs of the Hemiptera-Lygaeidae-Blissinae eat seeds of Haemodoroideae from South Africa; most bugs of this clade are sap-eaters (Slater 1976).
Chemistry, Morphology, etc. There is clearly much variation in basic floral organization in this small family. The median petal is abaxial in monosymmetric flowers of Haemodoroideae such as Wachendorfia, i.e., the flowers are inverted (this has only two septal nectaries - Vogel 1998b), while in Anigozanthus zygomorphy is evident as a slit down one side of a tube formed by the six connate tepals - the plane of symmetry must necessarily be slightly oblique here. As Eichler (1880) noted, if flowers are examined early in development, Wachendorfia has flowers with transverse symmetry, while in Anigozanthus they are oblique. Taxa like Xiphidium have a more or less differentiated perianth with the two whorls each fully encircling the apex; the three stamens are borne opposite the petals/inner tepals, while Anigozanthus has six stamens individually opposite the six perianth lobes (see illustrations in Simpson 1990). The ovary may be secondarily superior (Simpson 1998a); the septal nectaries are found below the point of insertion of perianth (see especially Simpson 1993). The outer periclinal wall of the testa is thick.
Some general information is taken from Simpson (1990, 1998b); for an extensive anatomical survey of the family, see Aerne-Hains and Simpson (2016), for variation in the pollen of Conostylis, see Pierce and Simpson (2009), and for the embryology of Lachnanthes caroliniana, see Simpson (1988).
Phylogeny. The phylogeny of the family has been quite extensively studied (e.g. Hopper et al. 1999). Within Conostyloideae, Tribonanthes is sister to the rest - and it is morphologically quite distinct (Hopper et al. 2009).
PONTEDERIACEAE Kunth, nom. cons. Back to Commelinales
Water or marsh plants; vegetative stems indeterminate; (vessels also in stems); styloids or prismatic crystals 0 (+); stomatal subsidiary cells with oblique divisions; leaves spiral or spirally two-ranked, leaf blade broad, initially surrounding petiole of older leaf, (linear, whorled), petiolate (sessile), 2ndary veins transverse, sheath open or closed, often long-ligulate, "stipules" acicular to linear/0, colleters +; inflorescence with two inflorescence bracts; flowers open for one day, tristyly, enantiostyly common, mono-/polysymmetric; T (large), adaxial inner tepal with markings, deliquescent, (4, 3), mostly blue or yellow, ± connate, (tube to 11 cm long); A adnate to T, of different lengths, (1, 3, 4), (staminodes 2), filaments hairy, (winged); (tapetum glandular); pollen 2- or 3-sulcate; (septal nectaries 0); (1 carpel fertile), (placentation parietal), stigma small, dry; ovule (1/carpel), micropyle bistomal, parietal tissue none (single layer - Monochoria), (epidermal cells ± radially elongated), postament +; (fruit an achene surrounded by P base); (seed ridged); exotestal cells box-like, endotestal cells elongated, tranversely flattened, operculum 0?; micropylar endosperm haustorium +, embryo long, suspensor hardly developed; n = (7) 8(-13); cotyledon linear, bifacial.
2 [list]/33. Tropics, also temperate, esp. New World (map: Fl. N. Am. 26: 2002). [Photos - Collection.]
Age. Divergence within the crown-group Pontederiaceae is estimated to have begun around 39 m.y.a. (Janssen & Bremer 2004).
Evolution: Divergence & Distribution. Simpson and Burton (2006) discuss the evolution of features of floral anatomy in the family, including outgroups; the embedded [Pontederia + Reussia] not only have single, apical ovules in the single fertile carpel and an achene surrounded by perianth, but they are the only members of the family to have styloids or prismatic crystals. Other features Simpson and Burton (2006) studied also correlate with the clades evident in the phylogenetic analyses of Barrett and Graham (1997). De Sousa et al. (2015) focused on the evolution of vegetative and anatomical features in the family.
Pollination Biology & Seed Dispersal. Considerable work has been carried out on the floral biology of Pontederiaceae, where tristyly, enantiomorphy and monosymmetry (and Pontederia cordata, at least, is obliquely monosymmetric) are all well known. Graham and Barrett (1995) discussed the evolution of the breeding system, while Barrett and Graham (1997) outlined the phylogeny and diversification of the family and Kohn et al. (1996) the evolution of reproductive features. However, there have been problems with rooting the phylogenetic tree (see below, also Ness et al. 2011 and references). In the enantiostylous Monochoria there are five small stamens with yellow anthers and one large stamen with a blue anther (Wang et al. 1995 for pollination). Lunau (2006) suggests that the yellowish spot on the median-adaxial tepal member of some other Pontederiaceae mimics a stamen.
Chemistry, Morphology, etc. In Heteranthera, Eichhornia s. str. and Pontederia s. str. (at least) the blade of the first leaf of the axillary shoot completely encircles the main stem in bud, or the blade of the young leaf completely encircles the petiole of the next oldest leaf - this may be a unique arrangement (see also Eichler 1880). Although Hydrothrix gardneri, the only species that grows submerged, appears to have whorled, linear leaves, there is a single short, sheathing ligule at each node, the other "leaves" having narrower bases and are borne inside the sheath (Rutishauser 1999; Pellegrini 2017); there is only one bud and one vascular trace per node (Pellegrini 2017).
The endothecial walls of Eichhornia have distinctive base-plate thickenings (Manning & Goldblatt 1990).
Additional information is taken from Cook (1998: general), Tomlinson (1982: colleters), Endress (1995b: flowers), Strange et al. (2004: floral anatomy), Ono (1928: ovule development), Coker (1907: seed anatomy), and Tillich (1994: seedlings).
Phylogeny. Eichhornia currently is hopelessly para/polyphyletic, Pontederia and Monochoria being embedded in it (Graham et al. 1998; see also Ness et al. 2011; de Sousa et al. 2015). There have been persistent problems in rooting the tree (also Graham et al. 1998, esp. 2002), but a recent study suggests that Eichornea meyeri is sister to the rest of the family - although there are still some lingering doubts (Ness et al. 2011), and Du and Wang (2014) and Du et al. (2016) recovered Pontederia as sister to the other members of the family (Chinese) that they studied.
Classification. See Pellegrini (2017) for a two-genus classification of the family.
Synonymy: Heterantheraceae J. Agardh