EMBRYOPSIDA Pirani & Prado

Gametophyte dominant, independent, multicellular, not motile, initially ±globular; showing gravitropism; acquisition of phenylalanine lysase [PAL], microbial terpene synthase-like genes +, 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, sporopollenin + laid down in association with trilamellar layers [white-line centred lamellae; tripartite lamellae], >1000 spores/sporangium; nuclear genome size <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.

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].


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; 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].


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].


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.


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 apical meristem intermediate-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 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 [], 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 very small [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).

[CERATOPHYLLALES + EUDICOTS]: ethereal oils 0.

EUDICOTS: (Myricetin, delphinidin +), 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]; seed coat?

[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 whole nuclear genome duplication [palaeohexaploidy, gamma triplication], PI-dB motif +, small deletion in the 18S ribosomal DNA common.

[ROSIDS ET AL. + ASTERIDS ET AL.] / PENTAPETALAE: root apical meristem closed; (cyanogenesis also via [iso]leucine, valine and phenylalanine pathways); flowers rather stereotyped: 5-merous, parts whorled; P = calyx + corolla, the calyx enclosing the flower in bud, sepals with three or more traces, petals with a single trace; stamens = 2x K/C, in two whorls, internal/adaxial to the corolla whorl, alternating, (numerous, but then usually fasciculate and/or centrifugal); pollen tricolporate; G [5], G [3] also common, when [G 2], carpels superposed, placentation axile, style +, stigma not decurrent; compitum +; endosperm nuclear; fruit dry, dehiscent, loculicidal [when a capsule]; RNase-based gametophytic incompatibility system present; floral nectaries with CRABSCLAW expression; (monosymmetric flowers with adaxial/dorsal CYC expression).

[DILLENIALES [SAXIFRAGALES [VITALES + ROSIDS s. str.]]]: stipules + [usually apparently inserted on the stem].


[VITALES + ROSIDS] / ROSIDAE: anthers ± dorsifixed, transition to filament narrow, connective thin.

ROSIDS: (mucilage cells with thickened inner periclinal walls and distinct cytoplasm); if nectary +, usu. receptacular; embryo long; chloroplast infA gene defunct, mitochondrial coxII.i3 intron 0.



Age. Suggestions for the age of this node are (91-)85(-77) m.y. (N. Zhang et al. 2012) and about 105/112 or 112.9 m.y. (Tank et al. 2015: Table S1, S2 and Magallón et al. 2015 respectively); other estimates for stem Crossosomatales, i.e. this node, are 89-83 m.y. (Anderson et al. 2005), ca 106.7 m.y., Magallón and Castillo (2009), (108-)104, 97(-93) m.y., Wikström et al. (2001), two estimates of (112-)105(-98) and (88-)81(-74) m.y. by Hengchang Wang et al. (2009), (119-)108, 106(-99) m.y. by Bell et al. (2010) and ca 99.7 m.y. by Naumann et al. (2013). Check the topologies in all cases!

Evolution: Divergence & Distribution. The character "compound leaves" could be placed at this node; however, wherever it goes it is very homoplasious.

Phylogeny. See the Pentapetalae and Saxifragales pages for further discussions on the relationships of Crossosomatales.


?Nodes; lamina margins toothed; hypanthium +, with nectary; G stipitate, styluli +, postgenital connation +, compitum present only near stigma, stigma wet; ovules apotropous, micropyle bistomal [zig-zag], both integuments 4 or more cells across; seed testal, walls of outer layers much thickened. - 7 families, 12 genera, 66 species.

Age. Wikström et al. (2001) dated the beginning of diversification here to (99-)95, 91(-87) m.y.a. The age of crown group Crossosomatales was also variously estimated as (94-)88(-82) and (57-)51(-45) m.y., Bayesian relaxed clock estimates being up to 100 m.y., by Hengchang Wang et al. (2009), and also (110-)92, 84(-61) m.y. (Bell et al. 2010) and about 84.6 m.y. (Magallón et al. 2015).

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: Divergence & Distribution. Oh (2009, 2010) discussed the complex biogeography of the group; there is a Northern/Southern Hemisphere split within it, i.e. the first four families versus the second three families; both vicariance and long distance dispersal seem to be involved (see also Christenhusz & Chase 2013).

Matthews and Endress (2005a, 2006b for a summary) emphasised a number of distinctive features of the order, even if exactly where some of these are to be placed on the tree is unclear. For instance, the funicular vascular bundle ends undivided in the chalaza in Stachyuraceae and some Staphyleaceae, whereas it splits into 3-6 short bundles in the other families (Geissolomataceae were not studied). Is a divided bundle an apomorphy for the order (or larger group), lost in the Staphlyeaceae-Crossosomataceae clade, and so a synapomorphy for it, but then regained in Crossosomataceae itself? Or is its distribution to be explained by some other combination of gains and losses (the distribution of "luminous" stylar canals and loculi may be similar)? Matthews and Endress (2005a, 2006b) also note that there is much more in common between members of Crossosomatales in the broad sense (as delimited below) than between Crossosomataceae, Stachyuraceae, and Staphyleaceae included in some narrow circumscriptions of the order.

Chemistry, Morphology, etc. For a survey of wood anatomy, with a listing of the features - possibly plesiomorphic - common to the whole order, see Carlquist (2007c). For the distribution of characters of floral morphology in the group, I largely follow the excellent study by Matthews and Endress (2005a), which should be consulted for more details, alternative interpretations of states, etc. The inner integument in particular may be only three cells thick (Crossosoma, Geissoloma).

Phylogeny. Crossosomatales are a surprising group, but they are likely to be monophyletic. Details of some of the relationships in the tree below like [[Aphloiaceae + Ixerbaceae] [Staphyleaceae [Stachyuraceae + Crossosomataceae]]] (D. Soltis et al. 1999, 2000; c.f. in part Koontz and Soltis 1999) and [Geissolomataceae [Staphyleaceae [Stachyuraceae + Crossosomataceae]]] (rbcL tree in Nandi et al. 1998) have been suggested; see also Savolainen et al. (2000a). The tree is based on these studies, and in particular those of Sosa and Chase (2003), Oh and Potter (2006), Soltis et al. (2007a) and Oh (2009: Aphloiaceae not included). Crossosomatales as a whole are usually not very strongly supported, although they have 1.0 p.p. in Soltis et al. (2007a). The distinctive Guametala has been added to Crossosomatales (Oh & Potter 2006: three genes); it has strong support as sister to [Stachyuraceae + Crossosomataceae], although the position of Stachyuraceae was not stable in the analyses of Oh (2009, but see Oh 2010). M. Sun et al. (2016) also recovered the relationships followed here.

In an analysis of mitochondrial genes, Qiu et al. (2010) found that Zygophyllales were embedded in Crossosomatales, but with only moderate support (sister to Aphloia! - long branch attraction?); the combined clade was poorly supported. Does Gumillea (ex Cunoniaceae) belong here? It has no characters suggesting a particular position anywhere...

Classification. This is a remarkably heterogeneous group, as Oh and Potter (2006) mentioned as they rather reluctantly decided to place Guamatela in a monotypic family.

Crossosomatales tree

Includes Aphloiaceae, Crossosomataceae, Geissolomataceae, Guamatelaceae, Stachyuraceae, Staphyleaceae, Strasburgeriaceae.

Synonymy: Crossosomatinae Reveal, Geissolomatinae Reveal - Geissolomatales Reveal, Staphyleales Martius - Crossosomatanae Doweld

[Staphyleaceae [Guamatelaceae [Stachyuraceae + Crossosomataceae]]]: leaves or leaflets involute; inflorescence terminal; stigma ± expanded.

Age. The age of Crossosomatales, crown group, at 47-40 m.y., properly refers to this clade (Anderson et al. 2005). Other estimated ages for this node include (68-)62, 56(-50) m.y. (Wikström et al. 2001), ca 76.3 m.y. (Magallón & Castillo 2009), (48-)37, 34(-14) m.y. (Bell et al. 2010), as much as ca 106.8 m.y. (Tank et al. 2015: Table S1 - older than stem age of Crossosomatales...; 49.5 m.y. Table S2) and as little as around 31.3 m.y. (Magallón et al. 2015).

STAPHYLEACEAE Martynov, nom. cons.   Back to Crossosomatales


Evergreen to deciduous shrubs to trees; ellagic acid 0; wood often fluorescing; fibres with bordered pits; nodes 3:3, 5:5; petiole bundles (interrupted) annular; mucilage cells +; stomata anisocytic; cuticle waxes as (parallel) platelets; leaves opposite, odd-pinnately compound (uni-, trifoliolate), "glands" or stipels at articulations, stipules interpetiolar or not; K ± petal-like, stamens = and opposite sepals, filaments flattened, anthers sagittate; pollen microreticulate; G connate, [2-3(4)], odd member adaxial; (1-)6-12 ovules/carpel, (basal), orientation variable, outer integument ca 6 cells across, inner integument 3-4 cells across, parietal tissue 3-5 cells across, (nucellar cap +); fruit indehiscent, a berry, or dry, inflated, K persistent or not; seeds few, hilum well developed, with 3-several scars of vascular strands in a horseshoe (not); testa multiplicative, (vascularized), many cells across, exotesta palisade (spongy - "Euscaphis"), mesotesta thick-walled, endotesta slightly thick-walled, unlignified, tegmen multiplicative, ca 10 cells across, crushed; embryo chlorophyllous, cotyledons large; n = (11-)13(-14).

2[?][list]/45: Staphylea (23), Dalrympelea (20-25). North temperate, tropics in America (to Bolivia) and Malesia (map: see van der Linden 1960; Meusel et al. 1978; Tiffney 1979). [Photo - Fruit, Staphylea Flower, Fruits.]

Evolution: Divergence & Distribution. Turpinia has an extensive fossil record in the northern hemisphere from the Eocene onwards (Tiffney 1979 for a review); for fossils of Staphylea, which are Oligocene or younger, see Y.-J. Huang et al. (2015).

Chemistry, Morphology, etc. Dickison (1987b) noted the distinctive nodal anatomy of the family, with small accessory traces from the central bundle going to the leaves. The pollen is binucleate according to Kimoto and Tokuoka (1999).

See Hegnauer (1973, 1990: chemistry), Lobreau-Callen (1977: pollen), Carlquist and Hoekman (1985: wood anatomy), Dickison (1986a: floral morphology, 1987a: pollen morphology, 1987b: vegetative anatomy), Ramp (1987: gynoecium), Guérin (1901) and Riddle (1905), ovules, Guérin (1901), Tiffney (1979), and Danilova (1996), all seed structure, and Simmons (2006: general).

Phylogeny. Simmons and Panero (2000: abstract) thought that genera in Staphyleaceae were polyphyletic. Other work suggests that relationships in the family are [Euscaphis [Staphylea + Turpinia]] (Wen et al. in Huang et al. 2015); a full phylogeny of the family is needed!

Taxonomy. The limits of the genera accepted until recently, based on fruit morphology, are thought to be unsatisfactory (Simmons & Panero 2000); Simmons (2006) realigned the genera, but see above.

Previous Relationships. Staphyleaceae were placed in Sapindales by Cronquist (1981) and Takhtajan (1997). Tapiscia and Huertea have long been recognised as being rather different from other Staphyleaceae, i.a. having spirally-arranged leaves (see Dickison 1987 for a convenient table of differences). Molecular data suggest that they are not at all closely related, and here they are included in Huerteales.

Synonymy: Ochranthaceae A. Jussieu

[Guamatelaceae [Stachyuraceae + Crossosomataceae]]: funicular aril +.

Age. The age of this node is about 26 m.y. (Magallón et al. 2015).

GUAMATELACEAE S. Oh & D. Potter   Back to Crossosomatales


Sprawling evergreen shrub; ellagic acid ?; nodes 3:3; petiole bundles annular; stomata ?; leaves opposite, lamina ?vernation, venation palmate, lower surface tomentose; ?inflorescence; K coloured, C spathulate; A 10, anthers sagittate; pollen membranes protruding through apertures, surface microreticulate; G 3; ovules many/carpel, biseriate; fruit a follicle, K persistent; seeds many; endosperm scanty; n = ?

1[list]/1: Guamatela tuerckheimii. Mexico, Guatemala, and Honduras (map: approximate only).

Chemistry, Morphology, etc. Anatomy, embryology, and chemistry are largely unknown.

Previous Relationships. Guamatela used to be included in Rosaceae (Oh & Potter 2002; Potter 2003), and it does indeed look faintly Rubus-like.

[Stachyuraceae + Crossosomataceae]: crystals/druses absent from flowers, anthers X-shaped; whole testa sclerotic.

Age. Stachyuraceae and Crossosomataceae may have diverged (40-)26, 24(-12) m.y.a. (Bell et al. 2010), ca 44 m.y.a. (Tank et al. 2015: Table S2), (49-)44, 42(-373) m.y.a. (Wikström et al. 2001), 68.25±10.36 m.y.a. (Zhu et al. 2006), or as little as 23.4 m.y.a. (Magallón et al. 2015).

STACHYURACEAE J. Agardh, nom. cons.   Back to Crossosomatales


Evergreen or deciduous shrubs or small trees; ellagic acid +; true tracheids +; petiole bundle(s) arcuate; hairs eglandular, (cuticle waxes as tubes); stomata paracytic; leaves spiral; inflorescences long-racemose, axillary; flowers 4-merous, hypanthium 0; K decussate; A 2x K; pollen grains (tricellular), psilate; nectary at base of G; G [4], opposite sepals, placentation intrusive apical-parietal, style +, compitum +, scapitate-peltate; ovules many/carpel, biseriate, parietal tissue ca 3 cells across, obturator +; megaspore mother cells several, antipodal cells degenerate; fruit a berry, K deciduous; seeds many, coat multiplicative, tegmen obliterated; embryo moderate, cotyledons large; n = (11) 12.

1[list]/5. South East Asia (map: from Li 1943; Chen 1981). [Photo - Habit/Fruits, Inflorescence]

Chemistry, Morphology, etc. The leaves have veins running to opaque, deciduous teeth. The stomata are reported as being anomocytic (Beauvisage 1920; Schneider 2006). Although the flowers appear to be perfect, Schneider (2006) suggests that cryptic dioecy may be the norm. For pollen, see Jin and Wei (2002); they described the surface as being foveate and the grains as being 18-28µm in size, larger than those of Tapiscia (see Tapisciaceae, Huerteales) but smaller than the finely reticulate grains of Staphyleaceae (28-40µm). The micropyle is zig-zag and there is a massive nucellus.

Details of the flower are taken from Hooker (1882) and of embryology from Mauritzon (1936b), Mathew and Chaphekar (1977) and Kimoto and Tokuoka (1999); see Beauvisage (1920) for some anatomy, Hegnauer (1973, 1990) for chemistry, Chen (1981) for a revision of most of the species, Schneider (2006) for general information, and Zhu et al. (2006) for a phylogeny.

Previous Relationships. Stachyuraceae were included in Theales by Takhtajan (1997).

CROSSOSOMATACEAE Engler, nom. cons.   Back to Crossosomatales


Deciduous shrubs; inulin, ellagic acid +; vessel elements with simple perforation plates; nodes also 1:1; yellow acicular crystals common; leaves spiral or opposite, "small", (margins entire), stipules minute, petiolar or 0; (plant polygamo-monoecious); flowers often axillary, solitary; flowers (3-)4-5(-6)-merous, (nectary 0); A 4-many, opposite sepals or from 10 trunk bundles; tapetal cells polyploid; pollen microreticulate; G 1-5(-9), odd member adaxial, styluli short, stigma also decurrent; ovules (1-)2-many/carpel, pleurotropous, amphi- or campylotropous, outer integument ca 7 cells across, inner integument ca 4 cells across, parietal tissue 4-7(?<) cells across, (nucellar cap +); megaspore mother cells several; fruit a follicle; seed with fimbriate aril, endotegmen fibrous; n = 6.

4[list]/12. W. North America (map: from Hannon 2002). [Photo - Crossosoma Collection]

Chemistry, Morphology, etc. Velascoa has a long hypanthial tube, but it apparently lacks a nectary.

Information is taken from Hegnauer (1964, 1989: chemistry), P. E. Richardson (1968: general), Mauritzon (1939a) and Kapil (1970), both embryology, etc., DeBuhr (1978: wood anatomy), Tatsuno and Scogin (1978: chemistry), Thorne and Scogin (1978: inclusion of Forsellesia), Rzedowski and Rzedowski (1997: new genus), Hannon (2002: review), and Sosa (2006: general summary).

Phylogeny. For relationships within the family, see Sosa and Chase (2003); Crossosoma may be sister to the rest.

Previous Relationships. Crossosomataceae were included in Rosales by Cronquist (1981) and were sister taxon to Geraniaceae in some early molecular studies (e.g. Price & Palmer 1993); Takhtajan (1997) included a monofamilial Crossosomatales in his Rosidae.

[Aphloiaceae [Geissolomataceae + Strasburgeriaceae]]: conspicuous protrusions from pollen apertures ["pollen buds"].

Age. The age of this node is around (101-)82, 75(-53) m.y. (Bell et al. 2010), (86-)81(-76) m.y.a. (Wikström et al. 2001), about 69.7 m.y. (Magallón et al. 2015) or about 93.9 m.y. (Tank et al. 2015: Table S1, S2).

APHLOIACEAE Takhtajan   Back to Crossosomatales


Evergreen shrubs or trees; cork pericyclic; tracheids dimorphic; rays of two different widths; vasicentric or apotracheal parenchyma; petiole bundles arcuate; stomata anisocytic; plant glabrous; leaves two-ranked; inflorescence fasciculate, axillary; P +, ?spiral, ca 7; A many; pollen striate; G 1, style 0, stigma annular-peltate-bilobed; ovules ca 10/carpel, micropyle endostomal; fruit a berry, P and A persistent; testa with outer 3-5 cell layers much thickened, then small unthickened cells, then 2-3 layers of elongated unthickened cells; endosperm development?; embryo curved, terete; n = ?

1[list]/1 or more: Aphloia theiformis. E. Africa, Madagascar, the Mascarenes and Seychelles (map: from Trop. Afr. Fl. Pl. Ecol. Distr. 1. 2003). [Photo - Fruit]

Chemistry, Morphology, etc. The hypanthial region is broad and spreading and its surface may be nectariferous. The ovules are possibly campylotropous and are not simply anatropous.

Details of the seed coat are in part taken from Takhtajan (1992), for wood anatomy, see Miller (1975), while Hegnauer (1989, as Flacourtiaceae) gives a few details of plant chemistry; see Kubitzki (2006b) for a summary.

Classification. Oh (2010) suggested that there is considerable sequence variation in Aphloia; detailed study of the variation pattern within this genus are needed, and there is probably more than a single species.

Previous Relationships. Aphloia used to be included in Flacourtiaceae, although it is different anatomically (Miller 1975); it was included as a separate family in Violales by Takhtajan (1997).

[Geissolomataceae + Strasburgeriaceae]: hairs single-celled, lignified and T-shaped; pollen ± smooth; G synascidiate, not stipitate, alternate with P/K, abaxially ridged, style long, towards tips twisted, postgenitally united at apex, stigma punctiform; ovules two/carpel, collateral, pendant; fruit a capsule, terminated by persistent style; hilum on seed large.

Age. This clade is about 51.6 m.y.o. (Magallón et al. 2015).

Evolution: Divergence & Distribution. Matthews and Endress (2006b) emphasize the synapomorphies of this clade.

GEISSOLOMATACEAE A.-L. de Candolle, nom. cons.   Back to Crossosomatales


Evergreen shrubs; plants Al-accumulators; cork cambium outer cortical; nodes 1:1; leaves opposite, lamina margins entire, apex mucronate, secondary veins palmate, paired projections [?stipules] on petioles; flowers single, axillary, with 3-4 pairs of basal bracts; flower 4-merous; P +, uniseriate, 4, petal-like, basally connate; A adnate to base of P, obdiplostemonous; G [4], alternate with P; ovules apotropous, micropyle exostomal, hypostase +; fruit a loculicidal capsule, surrounded by persistent K; seed with funicular caruncle; coat with thick-walled cells; endosperm development?, embryo ?small, cotyledons thin; n = ?

1[list]/1 (Geissoloma marginatum). Cape Province, South Africa (map: from Heywood 1978).

Chemistry, Morphology, etc. For information on nodal anatomy, R. A. Howard (pers. comm.); general information is taken from Baillon (1875), Dahlgren in Dahlgren and van Wyk (1988, "micropyle endostomal", but c.f. Stephens 1909a and Forest 2006); leaf anatomy from Carlquist (1990a), seed coat from Danilova (1996).

Previous Relationships. Geissolomataceae were included in Celastrales by Cronquist (1981), in Ericanae by Takhtajan (1997).

STRASBURGERIACEAE van Tieghem, nom. cons.   Back to Crossosomatales

Evergreen trees; vessel elements long, with scalariform [>27 bars] perforation plates; cells with thickened mucilaginous inner tangential walls; acicular crystals +; leaves spiral, lamina margins gland-toothed; flowers large; K spiral, C clawed; filaments flattened, anthers ³3mm long; style hollow; ovules sessile, ?epitropous; x = 25.


Age. Crown-group Strasburgeriaceae are about 23.5 m.y.o. (Magallón et al. 2015).


1. Ixerba Cunningham

Non-hydrolysable tannins 0; cork?; pits vestured; petiole bundles arcuate; stipules 0; inflorescence umbellate, terminal; stamens = and opposite sepals; pollen 4-5-colporate; nectary on G, obscurely lobed, lobes opposite petals; G [5], style strongly ridged and obviously spiral at apex; parietal tissue ca 8 cells across, chalazal tissue massive funicular obturator +; fruit loculicidal, carpels also splitting adaxially, valves woody, reflexed, K deciduous; seeds shiny, "aril" broad, exotestal and adjacent cells thickened; endosperm development?, cotyledons large; n = 25.

1/1: Ixerba brexioides. North Island, New Zealand.

Synonymy: Ixerbaceae Doweld & Reveal

2. Strasburgeria Baillon

Chemistry?; stem with cortical bundles [= lateral foliar bundles]; nodes also 5:5; petiole bundles ± C-shaped, arcuate; calcium oxalate as ± spheroidal masses [epiderms/hypodermis]; cuticle waxes almost thread-like scales; lamina teeth with a single vein and opaque deciduous cap, stipules intrapetiolar, connate basally; flowers single, axillary; hypanthium 0; K 8-10, spiral, C 5 (6); A 10, in a single whorl, obdiplostemonous, anthers latrorse, connective thick, anther thecae attached their length to connective; base of ovary surrounded by erect flange with ten short "spokes" cupping filament bases; G [4-7], adnate to central column, stigmas lobed; ovule 1/carpel, outer integument 7-8 cells across, parietal tissue 8-10 cells across; fruit indehiscent, rather dry, K persistent; outer testa of 5-12 layers of crystalliferous sclereids; endosperm moderate; n = 250.

1/1: Strasburgeria calliantha. New Caledonia, on ultrabasic rocks (map: fossil localities green, from Jarzen & Pocknall 1993). [Photo - Flower]

Evolution: Divergence & Distribution. Caenozoic pollen like that of extant Strasburgeria, although rather smaller, has been found from Australia, Tasmania, and New Zealand (see Blufopollis scabratus: Jarzen & Pocknall 1993; Lee et al. 2001), and also off Wilkes Land, Antarctica, in deposits of Early Eocene age ca 51.9 m.y.a. (Pross et al. 2012; Contreras et al. 2103). This suggests that the genus was once quite widely distributed in the Antipodean-Antarctic area - but the age of the fossils is rather greater than molecular estimates of the family crown-group age.

Chemistry, Morphology, etc. In Ixerba glands like those of lamina margin are in a cauline stipular position in seedlings. Strasburgeria, at least, has a mucilaginous epidermis, and in both genera mucilaginous cells are found in the flower.

The vascular supply to the carpel walls in Strasburgeria is complex (Dickison 1981a, q.v. for much other information). The exact function of the complex ?nectariferous flange+spoke structure at the base of the ovary is unclear.

Details of anatomy of Ixerba are taken from Gregory (1998: in Escalloniaceae) and Hils (1985) while Hegnauer (1973, as Saxifragaceae) gives some information on chemistry and Mauritzon (1933) a little information on embryology; see Schneider (2006) for a summary. For Strasburgeria, see also Beauvisage (1920) for some anatomy, Dickison (2006) and Cameron (2001, esp. 2003) for information, and Oginuma et al. (2006) for the remarkable chromosome number.

Little is known about the embryology, etc., of these taxa.

Previous Relationships. As Amaral (1991) suggested, Strasburgeria is to be excluded from Ochnaceae, where it was often included - i.a. it lacks cristarque cells and has crassinucellate ovules. Ixerba was placed in Grossulariaceae by Cronquist (1981), in Brexiaceae (now in Celastraceae) by Airy Shaw (1966: note the specific epithet), and as a family in Rosidae-Brexiales by Takhtajan (1997).