EMBRYOPSIDA Pirani & Prado

Gametophyte dominant, independent, multicellular, thalloid, with single-celled apical meristem, showing gravitropism; rhizoids +, unicellular; flavonoids + [absorbtion of UV radiation]; protoplasm dessication tolerant [plant poikilohydric]; cuticle +; cell walls with (1->4)-ß-D-glucans [xyloglucans], lignin +; several chloroplasts per cell; glycolate metabolism in leaf peroxisomes [glyoxysomes]; centrioles in vegetative cells 0, metaphase spindle anastral, predictive preprophase band of microtubules, phragmoplast + [cell wall deposition spreading from around the spindle fibres], plasmodesmata +; antheridia and archegonia jacketed, stalked; spermatogenous cells monoplastidic, centrioles develop de novo, associated with basal bodies of flagellae, multilayered structure +, proximal end of basal bodies lacking symmetry, stellate pattern associated with doublet tubules of transition zone; spermatozoids with a left-handed coil; male gametes with 2 lateral flagellae; oogamy; diploid embryo initially surrounded by haploid gametophytic tissue, plane of first division horizontal [with respect to long axis of archegonium/embryo sac], suspensor/foot +, cell walls with nacreous thickenings; sporophyte multicellular, sporangium +, single, with polar transport of auxin, dehiscence longitudinal; meiosis sporic, monoplastidic, microtubule organizing centre associated with plastid, cytokinesis simultaneous, preceding nuclear division, sporocytes 4-lobed, with a quadripolar microtubule system; spores in tetrads, sporopollenin in the spore wall, wall with several trilamellar layers [white-line centred layers, i.e. walls multilamellate]; close association between the trnLUAA and trnFGAA genes on the chloroplast genome.

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 common ancestor of the group.

STOMATOPHYTES

Abscisic acid, ?D-methionine +; sporangium with seta, seta developing from basal meristem [between epibasal and hypobasal cells], sporangial columella + [developing from endothecial cells]; stomata +, anomocytic, cell lineage that produces them with symmetric divisions [perigenous]; underlying similarities in the development of conducting tissue and in rhizoids/root hairs; spores trilete; polar transport of auxins and class 1 KNOX genes expressed in the sporangium alone; MIKC, MI*K*C* and class 1 and 2 KNOX genes, post-transcriptional editing of chloroplast genes; gain of three group II mitochondrial introns.

[Anthocerophyta + Polysporangiophyta]: archegonia embedded/sunken in the gametophyte; sporophyte long-lived, chlorophyllous, nutritionally largely independent of the gametophyte; sporophyte-gametophyte junction interdigitate, sporophyte cells showing rhizoid-like behaviour.

POLYSPORANGIOPHYTA†

Sporophyte well developed, branched, free living, sporangia several; spore walls not multilamellate [?here]; apical meristem +.

EXTANT TRACHEOPHYTA / VASCULAR PLANTS

Photosynthetic red light response; water content of protoplasm relatively stable [plant homoiohydric]; control of leaf hydration passive; (condensed or nonhydrolyzable tannins/proanthocyanidins +); vascular tissue +, sieve cells + [nucleus degenerating], tracheids +, in both protoxylem and metaxylem; endodermis +; root xylem exarch [development centripetal]; stem with an apical cell; branching dichotomous; leaves spirally arranged, blades with mean venation density 1.8 mm/mm2 [to 5 mm/mm2]; sporangia adaxial on the sporophyll, derived from periclinal divisions of several epidermal cells, wall multilayered [eusporangium]; columella 0; tapetum glandular; gametophytes exosporic, green, photosynthetic; stellate pattern split between doublet and triplet regions of transition zone; placenta with single layer of transfer cells in both sporophytic and gametophytic generations, embryonic axis not straight [root lateral with respect to the longitudinal axis; plant homorhizic].

[MONILOPHYTA + LIGNOPHYTA]

Branching ± monopodial; lateral roots +, endogenous, root apex multicellular, root cap +; tracheids with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangia borne in pairs and grouped in terminal trusses, dehiscence longitudinal, a single slit; cells polyplastidic, microtubule organizing centres not associated with plastids, diffuse, perinuclear; male gametes multiflagellate, basal bodies staggered, blepharoplasts paired; chloroplast long single copy ca 30kb inversion [from psbM to ycf2].

LIGNOPHYTA†

Plant woody; lateral root origin from the pericycle; branching lateral, meristems axillary; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].

EXTANT SEED PLANTS / SPERMATOPHYTA

Plant evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins derived from (some) sinapyl and particularly coniferyl alcohols [hence with p-hydroxyphenyl and guaiacyl lignin units, so no Maüle reaction]; root with xylem and phloem originating on alternate radii, vascular tissue not medullated, cork cambium deep seated; arbuscular mycorrhizae +; shoot apical meristem interface specific plasmodesmatal network; stem with vascular cylinder around central pith [eustele], phloem abaxial [ectophloic], endodermis 0, xylem endarch [development centrifugal]; 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 +; stem cork cambium superficial; branches exogenous; leaves with single trace from vascular sympodium [nodes 1:1]; stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; leaves with petiole and lamina, development basipetal, blade simple; axillary buds +, (not associated with all leaves); prophylls two, lateral; plant heterosporous, sporangia borne on sporophylls; microsporophylls aggregated in indeterminate cones/strobili; true pollen +, grains mono[ana]sulcate, exine and intine homogeneous; ovules unitegmic, parietal tissue 2+ cells across, megaspore tetrad linear, functional megaspore single, chalazal, lacking sporopollenin, megasporangium indehiscent; pollen grains landing on ovule; male gametophyte development initially endosporic, lacking chlorophyll, tube developing from distal end of grain, gametes two, developing after pollination, with cell walls; female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large" [ca 8 mm3], but not much bigger than ovule, with morphological dormancy; embryo cellular ab initio, endoscopic, plane of first cleavage of zygote transverse, suspensor +, short-minute, embryonic axis straight [shoot and root at opposite ends; plant allorhizic], white, cotyledons 2; plastid transmission maternal; ycf2 gene in inverted repeat, whole nuclear genome duplication [zeta duplication], two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], nrDNA with 5.8S and 5S rDNA in separate clusters; mitochondrial nad1 intron 2 and coxIIi3 intron and trans-spliced introns present.

ANGIOSPERMAE / MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], S [syringyl] lignin units common [positive Maüle reaction - syringyl:guaiacyl ratio more than 2-2.5:1], and hemicelluloses as xyloglucans; root apical meristem intermediate-open; root vascular tissue oligarch [di- to pentarch], lateral roots arise opposite or immediately to the side of [when diarch] xylem poles; origin of epidermis with no clear pattern [probably from inner layer of root cap], trichoblasts [differentiated root hair-forming cells] 0, exodermis +; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, associated gelatinous fibres [g-fibres] with innermost layer of secondary cell wall rich in cellulose and poor in lignin; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, wood parenchyma +; sieve tubes enucleate, sieve plate with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, cytoplasm not occluding pores of sieve plate, companion cell and sieve tube from same mother cell; sugar transport in phloem passive; nodes 1:?; stomata brachyparacytic [ends of subsidiary cells level with ends of pore], outer stomatal ledges producing vestibule, reduction in stomatal conductance to increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, venation hierarchical-reticulate, secondary veins pinnate, veins (1.7-)4.1(-5.7) mm/mm2, endings free; most/all leaves with axillary buds; flowers perfect, pedicellate, ± haplomorphic, parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P +, 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], ± embedded in the filament, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally, endothecium +, endothecial cells elongated at right angles to long axis of anther; (tapetum glandular), cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine +, thin, compact, lamellate only in the apertural regions; nectary 0; carpels present, superior, free, several, ascidiate, with postgenital occlusion by secretion, stylulus short, hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, dry [not secretory]; ovules few [?1]/carpel, marginal, anatropous, bitegmic, micropyle endostomal, outer integument 2-3 cells across, often largely subdermal in origin, inner integument 2-3 cells across, often dermal in origin, parietal tissue 1-3 cells across [crassinucellate], nucellar cap?; megasporocyte single, hypodermal, functional megaspore, chalazal, lacking cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; supra-stylar extra-gynoecial compitum +; ovule not increasing in size between pollination and fertilization; pollen grains landing on stigma, bicellular at dispersal, mature male gametophyte tricellular, germinating in less than 3 hours, pollination siphonogamous, tube elongated, 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, flagellae 0, double fertilization +, ovules aborting unless fertilized; P deciduous in fruit; seed exotestal, much larger than ovule at time of fertilization; endosperm diploid, cellular, heteropolar [micropylar and chalazal domains develop differently, 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; dark reversal Pfr -> Pr; Arabidopsis-type telomeres [(TTTAGGG)n]; 2C genome size 1-8.2 pg [1 pg = 109 base pairs], whole nuclear genome duplication [epsilon duplication]; protoplasm dessication tolerant [plant poikilohydric]; ndhB gene 21 codons enlarged at the 5' end, single copy of LEAFY and RPB2 gene, knox genes extensively duplicated [A1-A4], AP1/FUL gene, paleo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]].

[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]]]]: vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood +; tectum reticulate; anther wall with outer secondary parietal cell layer dividing; carpels plicate; 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 [possible position]; pollen tube growth intra-gynoecial; 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; K/outer P members with three traces, ("C" +, with a single trace); A few, (polyandry widespread, initial primordia 5, 10, or ring, ± centrifugal), 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]: ?

CORE EUDICOTS / GUNNERIDAE: (ellagic and gallic acids +); leaf margins serrate; compitum + [one place]; micropyle?; 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, compitum +, placentation axile, style +, stigma not decurrent; endosperm nuclear; fruit dry, dehiscent, loculicidal [when a capsule]; RNase-based gametophytic incompatibility system present; floral nectaries with CRABSCLAW expression.

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

[SAXIFRAGALES [VITALES + ROSIDS]] / ROSANAE Takhtajan / SUPERROSIDAE: ??

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

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

ROSID II / MALVIDAE / [[GERANIALES + MYRTALES] [CROSSOSOMATALES [PICRAMNIALES [SAPINDALES [HUERTEALES [MALVALES + BRASSICALES]]]]]]: ?

[CROSSOSOMATALES [PICRAMNIALES [SAPINDALES [HUERTEALES [MALVALES + BRASSICALES]]]]]: ?

Age. A suggestion for the age of this node is (91-)85(-77) m.y. (N. Zhang et al. 2012); 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 Dilleniales and the Saxifragales pages for further discussions on the relationships of Crossosomatales.

CROSSOSOMATALES Reveal  Main Tree.

?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 diversification in this clade 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., with Bayesian relaxed clock estimates up to 100 m.y. by Hengchang Wang et al. (2009), and also (110-)92, 84(-61) m.y. (Bell et al. 2010).

Note: Possible apomorphies are in bold. However, the actual level at which many of these features, particularly the more cryptic ones, should be assigned is unclear. This is partly because many characters show considerable homoplasy, in addition, basic information for all too many 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 is the not-so-trivial issue of how 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 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). Some relationships within the group remain unclear and 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).

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) and (48-)37, 34(-14) m.y. (Bell et al. 2010).

STAPHYLEACEAE Martynov, nom. cons.   Back to Crossosomatales

Staphyleaceae

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 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 green, 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. The family has an extensive fossil record in the northern hemisphere from the Eocene onwards (Tiffney 1979 for a review).

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).

Taxonomy. The limits of the genera accepted until recently, based on fruit morphology, have turned out to be unsatisfactory (Simmons & Panero 2000); see Simmons (2006) for genera now recognized.

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 +.

GUAMATELACEAE S. Oh & D. Potter   Back to Crossosomatales

Guametalaceae

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 = ?

1/1: 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 (49-)44, 42(-373) m.y.a. (Wikström et al. 2001), 68.25±10.36 m.y.a. (Zhu et al. 2006) or (40-)26, 24(-12) m.y.a. (Bell et al. 2010).

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

Stachyuraceae

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

Crossosomataceae

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) or (86-)81(-76) m.y.a. (Wikström et al. 2001).

APHLOIACEAE Takhtajan   Back to Crossosomatales

Aphloiaceae

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 = ?

1/1 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 ± psilate; G synascidiate, not stipitate, alternate with P/K, with dorsal ribs, style long, towards tips twisted, postgenitally united, stigma punctiform; ovules two/carpel, collateral, pendant, epitropous; fruit a capsule, terminated by persistent style; hilum on seed large.

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

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

Geissolomataceae

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; G [4]; 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 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; 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; x = 25.

2/2. New Caledonia and New Zealand.

Ixerba

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 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.

Strasburgeria Baillon

Chemistry?; stem with cortical bundles; nodes also 5:5; 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, latrorse, connective thick, anther thecae attached their length to connective; nectary on G; G [4-7], adnate to central column, stigmas lobed; ovule 1/carpel; fruit indehiscent, rather dry, K persistent; outer testa of 5-12 layers of crystalliferous sclereids; endosperm moderate; n = 250.

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

Evolution. Divergence & Distribution. Tertiary 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.

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. The hilum is about the length of the seed. The vascular bundles in the receptacle are clustered.

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 (1981a, 2006) and Cameron (2001) for information, and Oginuma et al. (2006) for the remarkable chromosome count. For general information, see Cameron (2003), but 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).

Synonmy: Ixerbaceae Doweld & Reveal