EMBRYOPSIDA Pirani & Prado
Gametophyte dominant, independent, multicellular, initially ±globular, not motile, branched; showing gravitropism; glycolate oxidase +, glycolate metabolism in leaf peroxisomes [glyoxysomes], acquisition of phenylalanine lysase* [PAL], flavonoid synthesis*, microbial terpene synthase-like genes +, triterpenoids produced by CYP716 enzymes, CYP73 and phenylpropanoid metabolism [development of phenolic network], 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; 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, asymmetrical; oogamy; sporophyte +*, multicellular, growth 3-dimensional*, 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 [= 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]; plastid transmission maternal; nuclear genome [1C] <1.4 pg, main telomere sequence motif TTTAGGG, KNOX1 and KNOX2 [duplication] and LEAFY genes present, ethylene involved in cell elongation; chloroplast genome with close association between trnLUAA and trnFGAA genes [precursors for starch synthesis], tufA, minD, minE genes moved to nucleus; mitochondrial trnS(gcu) and trnN(guu) genes +.
Many of the bolded characters in the characterization above are apomorphies of more or less inclusive clades 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.
Sporophyte well developed, branched, branching dichotomous, potentially indeterminate; hydroids +; stomata on stem; sporangia several, terminal; spore walls not multilamellate [?here].
II. TRACHEOPHYTA / VASCULAR PLANTS
Sporophyte long lived, cells polyplastidic, 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]; PIN[auxin efflux facilitators]-mediated polar auxin transport; (condensed or nonhydrolyzable tannins/proanthocyanidins +); borate cross-linked rhamnogalactan II, xyloglucans with side chains uncharged [?level], in secondary walls of vascular and mechanical tissue; lignins +; roots +, often ≤1 mm across, root hairs and root cap +; stem apex multicellular [several apical initials, no tunica], 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 +; stomata numerous, involved in gas exchange; leaves +, vascularized, spirally arranged, blades with mean venation density ca 1.8 mm/mm2 [to 5 mm/mm2], all epidermal cells with chloroplasts; sporangia in strobili, sporangia adaxial, columella 0; tapetum glandular; sporophyte-gametophyte junction lacking dead gametophytic cells, mucilage, ?position of transfer cells; MTOCs not associated with plastids, basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; archegonia embedded/sunken [only neck protruding]; embryo 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 growth ± monopodial, branching spiral; roots endomycorrhizal [with Glomeromycota], 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; nuclear genome [1C] 7.6-10 pg [mode]; 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 axillary, buds exogenous; lateral root origin from the pericycle; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].
SEED PLANTS† / SPERMATOPHYTA†
Growth of plant bipolar [plumule/stem and radicle/root independent, roots positively geotropic]; 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, free-nuclear/syncytial to start with, walls then coming to surround the individual nuclei, process proceeding centripetally.
EXTANT SEED PLANTS
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]; roots often ≥1 mm across, stele diarch to pentarch, xylem and phloem originating on alternating radii, cork cambium deep seated, gravitropism response fast; 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.; branching by 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; embryo cellular ab initio, suspensor short-minute, embryonic axis straight [shoot and root at opposite ends], primary root/radicle produces taproot [= 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 event], 2C genome size (0.71-)1.99(-5.49) pg, two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], 5.8S and 5S rDNA in separate clusters.
IID. 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; epidermis probably originating 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, multiseriate rays +, wood parenchyma +; sieve tubes enucleate, sieve plates 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 randomly oriented, brachyparacytic [ends of subsidiary cells ± level with ends of guard cells], 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 = T, petal-like, 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 restricted to the apertural regions, thin, compact, intine in apertural areas thick, orbicules +, pollenkitt +; nectary 0; carpels present, superior, free, several, spiral, 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, four-celled [one module, egg and polar nuclei sisters]; ovule not increasing in size between pollination and fertilization; pollen grains bicellular at dispersal, germinating in less than 3 hours, siphonogamy, pollen tube unbranched, growing towards the ovule, between cells, growth rate (ca 10-)80-20,000 µm h-1, tube 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 gametophytes tricellular, gametes 2, lacking cell walls, ciliae 0, double fertilization +, ovules aborting unless fertilized; fruit indehiscent, P deciduous; mature seed much larger than fertilized ovule, small [<5 mm long], dry [no sarcotesta], exotestal; endosperm +, ?diploid [one polar nucleus + male gamete], 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 [2C] (0.57-)1.45(-3.71) [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 IR expansions, 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]; anther wall with outer secondary parietal cell layer dividing; tectum reticulate; 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 monosporic [spore chalazal], 8-celled, bipolar [Polygonum type], antipodal cells persisting; endosperm triploid.
[MONOCOTS [CERATOPHYLLALES + EUDICOTS]]: (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).
[CERATOPHYLLALES + EUDICOTS]: ethereal oils 0 [or next node up]; fruit dry [very labile].
EUDICOTS: (Myricetin +), asarone 0 [unknown in some groups, + in some asterids]; root epidermis derived from root cap [?Buxaceae, etc.]; (vessel elements with simple perforation plates in primary xylem); nodes 3:3; stomata anomocytic; flowers (dimerous), cyclic; protandry common; K/outer P members with three traces, ("C" +, with a single trace); A ?, filaments fairly slender, anthers basifixed; microsporogenesis simultaneous, pollen tricolpate, apertures in pairs at six points of the young tetrad [Fischer's rule], cleavage centripetal, wall with endexine; G with complete postgenital fusion, stylulus/style solid [?here], short [<2 x length of ovary]; seed coat?; palaeotetraploidy event.
[PROTEALES [TROCHODENDRALES [BUXALES + CORE EUDICOTS]]]: (axial/receptacular nectary +).
[TROCHODENDRALES [BUXALES + CORE EUDICOTS]]: benzylisoquinoline alkaloids 0; euAP3 + TM6 genes [duplication of paleoAP3 gene: B class], mitochondrial rps2 gene lost.
[BUXALES + CORE EUDICOTS]: mitochondrial rps11 gene lost.
CORE EUDICOTS / GUNNERIDAE: (ellagic and gallic acids +); leaf margins serrate; compitum + [one position]; micropyle?; γ genome duplication [allopolyploidy, 4x x 2x], x = 3 x 7 = 21, 2C genome size (0.79-)1.05(-1.41) pg, PI-dB motif +; small deletion in the 18S ribosomal DNA common.
[BERBERIDOPSIDALES + ASTERIDAE]: ?
ASTERIDAE / ASTERANAE Takhtajan: nicotinic acid metabolised to its arabinosides; (iridoids +); tension wood decidedly uncommon; C enclosing A and G in bud, (connate [sometimes evident only early in development, petals then appearing to be free]); anthers dorsifixed?; if nectary +, gynoecial; G , style single, long; ovules unitegmic, integument thick [5-8 cells across], endothelium +, nucellar epidermis does not persist; exotestal [!: even when a single integument] cells lignified, esp. on anticlinal and/or inner periclinal walls; endosperm cellular.
[ONCOTHECALES [LAMIIDAE/ASTERID I + CAMPANULIDAE/ASTERID II]] / CORE ASTERIDS / EUASTERIDS / GENTIANIDAE: plants woody, evergreen; ellagic acid 0, non-hydrolysable tannins not common; vessel elements long, with scalariform perforation plates; sugar transport in phloem active; inflorescence usu. basically cymose; flowers rather small [<8 mm across]; C free or basally connate, valvate, often with median adaxial ridge and inflexed apex ["hooded"]; A = and opposite K/P, free to basally adnate to C; G [#?]; ovules 2/carpel, apical, pendulous; fruit a drupe, [stone ± flattened, surface ornamented]; seed single; duplication of the PI gene.
ASTERID I / LAMIIDAE / [CARDIOPTERIDALES [GARRYALES, AQUIFOLIALES [ICACINALES [[GENTIANALES + BORAGINALES], VAHLIALES, SOLANALES, LAMIALES]]] - Back to Main Tree
? - 9 orders, 48 families, 2,534 genera, 51,468 species.
Age. Bell et al. (2010) estimate a crown-group age for this clade of (109-)99, 91(-80) Ma, K. Bremer et al. (2004a: c.f. topology) an age of ca 119 Ma, Magallón and Castillo (2009) an age of ca 96.85 Ma, and Nylinder et al. (2012: suppl.) an age of about 119.8 Ma, Lemaire et al. (2011b) date it to ca 102 Ma, Magallón et al. (2015) to around 101.5 Ma, Wikström et al. (2015: topology!) to (120-)114(-107) My; 96.4 Ma is the age of an (Oncothecaceae + Vahliaceae) clade in Tank et al. (2015: Table S1). - Check and integrate - Wikström et al. (2001) estimated an age of (112-)107, 100(-95) Ma for the crown group.
Evolution: Divergence & Distribution. For the evolution of pollen here, see L.-E Yang et al. (2020), but c.f. topology, etc., e.g. a sister relationship between Oncothecaceae and Icacinaceae is supported by pollen characters, and within Icacinaceae, Cassinopsis, now in Metteniusales, is sister to the rest of the family.
CARDIOPTERIDALES Takhtajan - Main Tree.
Shrubs or trees; iridoids +; vessel elements also with simple perforation plates, pits usually not bordered; apotracheal parenchyma and variants common; (styloids +); petiole bundle arcuate; stomata cyclocytic to anisocytic; hairs unicellular (adpressed); leaves two-ranked or spiral, lamina margin entire, tertiary venation ± obscure, stipules 0; inflorescence axillary; (pedicels articulated); A basifixed; tapetal cells binucleate; (pollen grains ± asymmetric); nectary +; G asymmetric, unilocular, adaxial carpel alone fertile; ovules 2, epitropous, with parietal tissue, integument vascularized, funicular obturator +; embryo sac breaking through the nucellar epidermis, antipodal cells ephemeral. fruit (asymmetric); seed (ruminate); endosperm nuclear/coenocytic. - 2 families, 17 genera, 138 species.
Includes Cardiopteridaceae, Stemonuraceae.
Note: In all node characterizations, boldface denotes a possible apomorphy, (....) denotes a feature the exact status of which in the clade is uncertain, [....] includes explanatory material; other text lists features found pretty much throughout the clade. Note that the precise 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: Divergence & Distribution. Kårehed (2001, 2002b) discussed the taxa in their current familial circumscriptions, while Lens et al. (2008a) provided a detailed anatomical survey in a phylogenetic context.
Chemistry, Morphology, etc.. For a summary of gynoecial variation here, see Kong et al. (2018); in Cardiopteridaceae in particular there is variation in which carpels have a style and which produce ovule(s), but our basic knowledge of gynoecial and ovular development is very poor. The two sides of the gynoecium/fruit are sometimes dramatically different in appearance, as in Medusanthera; this too needs to be related to gynoecial development (see also the euasterid node).
For additional information, see Sleumer (1942a, b, 1971a), Howard (1942b), and Utteridge et al. (2005), all general, also Kaplan et al. (1991: chemistry), Lens et al. (2008a: measurements = range of means and upper end of variation, Cardiopteris [immature] excluded) and Bailey and Howard (1941a-d), all vascular anatomy, Heintzelmann and Howard (1948: crystals and indumentum), van Staveren and Baas (1973) and Baas (1973a, 1974), all epidermis and stomata, Teo and Haron (1999: anatomy), Lobreau-Callen (1972, 1973, 1977, 1980: pollen), and Mauritzon (1936c), Fagerlind (1945a) and Padmanabhan (1961: Gomphandra), all embryology.
Phylogeny Discussion on the placement of the genera included in the Cardiopteridaceae and Stemonuraceae below can also be found elsewhere; nearly all genera in these two families used to be in Icacinaceae.
Classification. These two families have quite a lot in common morphologically, however, Kårehed (2001) recognised them as separate.
Previous Relationships. In addition to Cardiopteridales here, the genera that until a few years ago made up Icacinaceae s.l. are now included in the lamiids, i.e. as Icacinaceae s. str. (Icacinales), as well as in the campanulids in Apiales as Pennantiaceae and as Metteniusales, and as sister to all other core asterids as Oncothecales.
CARDIOPTERIDACEAE Blume, nom. cons. - Back to Aquifoliales
(Lianes); plants Al accumulators [?all], secoiridoids +; (vessel elements with scalariform perforation plates only - Citronella), 500-1,390(-1,950) µm long, fibres 2,190-2,970(-3,450) µm long; (articulated laticifers + - Cardiopteris); petiole bundles annular (+ medullary); stomata also anomocytic and paracytic; (lamina margins toothed/spiny), (secondary veins palmate); (plant dioecious, andromonoecious); (inflorescence branched, ultimate units clearly cymose or not), (bracts 0); K (free)/basally connate/cupular, quincuncial, (protective in bud - Cardiopteris), C (imbricate - Cardiopteris); A basally adnate to C/(not - Citronella), also dorsifixed; (pollen porate), (endoapertures enlarged - not Citronella); (nectary 0); G , odd carpel adaxial, (pseudoloculus - Pseudobotrys, Citronella), style usu. slender, about as long as ovary, (± laterally positioned), stigma truncate or capitate, (styles branched to the base, branches heteromorphic, two stout, subconnate, lobed and grooved, one slender, with capitate stigma – Cardiopteris); ovule (1), (integument not vascularized), (ategmic - Cardiopteris [for more details, see below]), parietal tissue 0/?ca 2 cells across; fruit (asymmetric - Gonocaryum), endocarp C-shaped in transverse section, (2-winged samara, wings horizontally striate, stout styles accrescent – Cardiopteris); testa thin, ?structure; endosperm (ruminate), (embryo long, with foliaceous cotyledons - Gonocaryum); n = 14 [Leptaulus].
5 [list]/43: Citronella (21). Tropics, inc. the Pacific, to Taiwan (map: from Sleumer 1971a, c; Utteridge & Brummitt 2007; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010).
Chemistry, Morphology, etc.. Leptaulus has a violet-colored flavonoid; in L. daphnoides the shoot apex aborts.
Tobe (2011b) clarified the gynoecial morphology of Cardiopteris and noted that there was a nectary on the bottom part of the gynoecium. Variation of carpel number in this clade is not well understood; in Cardiopteris the carpel with a functional stigma has no associated ovules, while the two abaxial carpels with non-functional stigmas each has a single ovule (Kong et al. 2014). The ovary apex, i.e., the apices of the abaxial carpels, develops into a fleshy appendage on the fruit; this and other distinctive features of Cardiopteris (Kong & Schori 2014) are likely to be autapomorphies for the genus, although the embryology of other members of the family is poorly known.
Indeed, the embryology and seed development of Cardiopteris are without parallel in other angiosperms. Kong et al. (2002) described the ovules of Cardiopteris as being ategmic, straight, tenuinucellate and with the egg at the chalazal end of the embryo sac, similarly, Kong et al. (2014; see also Kong & Schori 2014) described the megaspore mother cells as being at the end of the long, straight ovule near the chalaza while the zygote was at the other end (their Fig. 7J). Painstaking work by Tobe (2016) on C. quinqueloba has clarified what is happenening here. The ovule is pendant in the loculus, with neither micropyle nor integument and with procambial tissue lying alongside the developing embryo sac. Megasporogenesis occurs in a hypodermal cell at the tip of the ovule, perhaps the "micropylar" end, and the innermost megaspore develops into the embryo sac. This elongates rapidly, and the egg cell, which is at the "chalazal" end of the ovule, is fertilized after the pollen tube has grown down the funicle. The embryo develops very slowly, while the first division of the endosperm nucleus results in two cells, one of which pushes out of the "micropyle", ballooning out and completely filling the ovary loculus before dying. As the seed develops, aymmetric growth results in the "micropyle" coming to be at the base of the seed near the funicle, and the late-developing chalazal vascular bundle almost surrounds the seed. Periclinal divisions of the nucellar epidermis in the area opposite the chalazal bundle ("antiraphe"), give rise to a two-layered tissue that forms a sort of testa. Insofar as one can work out the orientation of the embryo sac, the egg cell + synergids are the three cells that would be the antipodal cells in a normal Polygonum embryo sac (see Tobe 2016 for details of the whole process).
For additional literature, see above, also Schori (2016a: general), Damtoft et al. (1993: iridoids), Lobreau-Callen (1982: pollen, Peripterygium), Baillon (1874: fruit), and Vera-Caletti and Wendt (2001: new genus described).
Phylogeny. Citronella was sister to the three other genera examined (Kårehed 2001); Pseudobotrys is sister to Citronella (Schori, in Schori & Furness 2014); the latter genus (and Cardiopteris) has an imbricate corolla.
Previous Relationships. The relationships of Cardiopteris, a vine with distinctive morphology, were previously paricularly obscure. It was included in Celastrales by Cronquist (1981) and near there by Takhtajan (1997).
Synonymy: Leptaulaceae van Tieghem, Peripterygiaceae G. King
STEMONURACEAE Kårehed - Back to Aquifoliales
Vessel elements in radial multiples, 600-1,510(-2,000) µm long, fibres 2,000-3,650(-4,500) µm long; (crystal sand in wood rays); petiole bundles arcuate + wing/annular + medullary; sclereids +/0; (plant glabrous); (plant dioecious); inflorescence often cymose, flowers 4-5(-7) merous; K ± connate, ± valvate, (C 0, minute); A radiating, (adnate to C), filaments often stout and with club-shaped hairs, and/or connective with appendages, or filaments thin; tapetal cells multinucleate, pollen (1-)3(-9)-porate, usu. ± prolate, surface microechinate (not - Lasianthera), (columellae enlarged, only around pores); nectary (unilateral), (0); (staminate flowers: pistillode +); (carpelate flowers: staminodes +/0); G ?; style 0, stigma broad; ovule with integument ca 10 cells across, parietal tissue 1-2 cells across, (nucellar cap ca 2 cells across); drupe asymmetric [the two sides very different, one with a fleshy "appendage" developing over the sulcus], (symmetric - Stemonurus), (pseudoloculus + – Cantleya), mesocarp with fibre bundles, inner mesoocarp with ridges and grooves on the side of the appendage, when present, endocarp cells at right angles to inner mesocarp cells; testa thick, outer cells thick-walled, elongate, inner cells not thickened, post-chalazal bundle +; n = 22; seedling with hypocotyl, phanerocotylar. ILLUSTRATION.
12 [list]/95: Gomphandra (55), Stemonurus (15). Tropics, esp. Indo-Malesia to Australia (Queensland) and the West Pacific (map: from Sleumer 1971a; Utteridge & Brummitt 2007; Trop. Afr. Fl. Pl. Ecol. Distr. 5. 2010; Schori et al. 2013).
Chemistry, Morphology, etc.. The family appears to lack stipules (c.f. Mabberley 2017).
The carpelate flowers of Gomphandra are monosymmetric, having a single reflexed staminode (M. Schori, pers. comm.). Schori et al. (2009) discuss fruit variation in the family,
For additional literature, see above; also Potgieter et al. (2016: general), Schori et al. (2009: pollen) and Schori (2016b: fibre bundles in the mesocarp).
Phylogeny. Lasianthera is sister to the other Stemonuraceae, but only five genera were sampled (Kårehed 2001).
Thanks. I am grateful to Melanie Schori for comments.