EXTANT SEED PLANTS

Plant woody, evergreen; nicotinic acid metabolised to trigonelline; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignins rich in guaiacyl units; true roots present, xylem exarch, branching endogenous; arbuscular mycorrhizae +; shoot apical meristem complex; stem with ectophloic eustele, endodermis 0, xylem endarch, branching exogenous; vascular tissue in t.s. discontinuous by interfascicular regions; vascular cambium + [xylem ("wood") differentiating internally, phloem externally]; wood homoxylous, tracheids +; tracheid/tracheid pits circular, bordered; sieve tube/cell plastids with starch grains; phloem fibers +; stem cork cambium superficial, root cork cambium deep seated; nodes ?; stomata ?; leaf vascular bundles collateral; leaves spiral, simple, axillary buds?, prophylls [including bracteoles] two, lateral, veins -5(-8) mm/mm²; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores] +, grains mono[ana]sulcate, exine and intine homogeneous, ovules unitegmic, crassinucellate, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development first endo- then exosporic, tube developing from distal end of grain, to ca 2 mm from receptive surface to egg, gametes two, with cell walls, with many flagellae; female gametophyte endosporic, initially syncytial, walls then surrounding individual nuclei; seeds "large", first cell wall of zygote transverse, embryo straight, endoscopic [suspensor +], short-minute, with morphological dormancy, white, cotyledons 2; plastid transmission maternal; two copies of LEAFY gene, PHY gene duplication, mitochondrial nad1 intron 2 and coxIIi3 intron present.

MAGNOLIOPHYTA

Plant woody, evergreen; lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, apigenin and/or luteolin scattered, cyanogenesis via tyrosine pathway [ANITA grade?], lignins derived from both coniferyl and sinapyl alcohols, containing syringaldehyde [in positive Maüle reaction, syringyl:guaiacyl ratio less 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; stem with 2-layered tunica-corpus construction; wood fibers and wood parenchyma +; reaction wood ?, with gelatinous fibres; starch grains simple; primary cell wall mostly with pectic polysaccharides; tracheids +; sieve tubes eunucleate, with sieve plate, companion cells from same mother cell that gave rise to the tube, the sieve tube with P-proteins; nodes unilacunar; stomata with ends of guard cells level with aperture, paracytic; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, vein endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, development in general centripetal, numbers unstable, P not differentiated, outer members not enclosing the rest of the bud, A many, with a single trace, introrse, filaments stout, anther ± embedded in the filament, tetrasporangiate, dithecal, with at least outer secondary parietal cells dividing, each theca dehiscing longitudinally by action of hypodermal endothecium, endothecial cells elongated at right angles to long axis of anther, tapetum glandular, binucleate, microspore mother cells in a block, microsporogenesis successive, pollen subspherical, binucleate at dispersal, trinucleate eventually, tectum continuous or microperforate, exine columellar, endexine thin, compact, lamellate only in the apertural regions, pollen germinating in less than 3 hours, tube elongated, growing at 80-600 µm/hour, with callose plugs and callose-based walls, penetrating between cells, siphonogamy, penetration of ovules within ca 18 hours , nectary 0, G free, several, ascidiate, with postgenital occlusion by secretion, few [?1] ovules/carpel, ovules marginal, anatropous, bitegmic, micropyle endostomal, integuments 2-3 cells thick, megasporocyte single, megaspore lacking sporopollenin and cuticle, chalazal, female gametophyte ?type, stylulus short, stigma ± decurrent, wet [secretory]; P deciduous in fruit; seed exotestal; double fertilisation +, endosperm ?diploid, cellular [first division oblique, micropylar end initially with a single large cell, chalazal end more actively dividing], copious, oily and/or proteinaceous, embryo cellular ab initio; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, 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 PHYA/PHYC gene pairs.

Possible apomorphies are in bold. Note that the actual level to which many of these features, particularly the more cryptic ones, should be assigned is unclear, because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied. Furthermore, details of relationships among gymnosperms will affect the level at which some of these characters are pegged.

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with scalariform perforation plates; nucleus of egg cell sister to one of the polar nuclei; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

ROSID II  Back to Main Tree

Flavonols +; (cambium storied); petiole bundle(s) annular; ca 2 ovules/carpel, style +; endosperm scanty.

Huerteales [Brassicales + Malvales]: ?

HUERTEALES Doweld  Main Tree, Synapomorphies.

Vessel elements with scalariform perforations; leaf margins toothed, stipules cauline; flowers small, C no bigger than K, stamens = and opposite sepals; endosperm +, embryo at most medium. - 3 families, 5 genera, 23 species.

For the association of the Tapisciaceae and Dipentodontaceae, see Peng et al. (2003), also James Horn (pers. comm.). None of the three genera in these two families is at all well known. Nor is Perrottetia, previously in Celastraceae, if only rather uneasily so; molecular data suggest that it is to be placed near Tapiscia (M. Simmons, in Matthews & Endress 2005b), a placement with which its morphology is in general agreement. Alford, when describing his Gerrardinaceae, found it formed a polychotomy with Huerteales (Perrottetia not included), Brassicales and Malvales, the combined group being rather poorly supported as sister to Sapindales. Given the possibly superficial but still striking similarity of Gerrardina eylesiana in particular to Perrottetia, and perhaps a similarity in seed coat anatomy of the two genera, and the rather similar flowers of other Huerteales and Gerrardinaceae (but not in androecial position!), the latter are included here for the time being, however, both the morphology, anatomy, and secondary chemistry of the whole group are badly in need of detailed investigation; the mechanical (lignified) layer of the seed may differ in its origin within the order.

Includes Dipentodontaceae, Gerrardinaceae, Perrottetia, Tapisciaceae.

Synonymy: Dipentodontales C. Y. Wu - Huerteanae Thorne & Reveal

TAPISCIACEAE Takhtajan  Back to Main Tree

Wood fluorescing; fibers with simple pits; nodes also 5:5; petiole bundle annular; mucilage cells +; stomata paracytic; leaves spiral, odd-pinnately compound or trifoliolate, glands or stipels at point of articulation; K connate or not, anthers extrorse[?], pollen colpate, disc +, not vascularized/0, G [2], septate or not, 1 basal erect ovule/carpel, style +, hollow, apically branched or styles ± separate, stigma?; fruit a drupe or berry; testa thin-walled, (mesotesta sclerotic), exotegmen rather massive, fibrous, with cross layer, chalaza ballooning into endosperm; endosperm ?type, embryo medium; n = 13.

2[list]/5. China (Tapiscia sinensis), West Indies and N. South America (Map: from Ying et al. 1993). [Photo - Fruit]

• Tapisciaceae can be recognised by their spirally arranged, stipulate, odd-pinnately compound or trifoliolate leaves with serrate margins and glands or even foliaceous stipels at the point of articulation of the petiolule with the rhachis; the rhachis collapses at the nodes when the leaf dries. The flowers are small.

Axial parenchyma is absent. The pollen of Tapisciaceae is smaller than that of Staphyleaceae, being only some 13-18 µm long (Jin & Wei 2002). There is quite a prominent disc in Huertea, but it is not vascularized (Dickison 1986; Danilova 1996). The embryo is up to about half the length of the seed, and is embedded in copious endosperm. In Tapiscia sinensis, at least, the fruit takes about eighteen months to develop (Liu et al. 2008).

The two genera that make up the family were long included in Staphyleaceae (see Dickison 1987b for a table of differences separating them from the rest of Staphyleaceae) and placed in Sapindales by Cronquist (1981), while a segregated Tapisciaceae were still included in Sapindales by Takhtajan (1997).

See Dickison (1986: floral morphology, 1987a: pollen morphology, 1987b: vegetative anatomy) and Wei et al. (2002: the pollen of Tapiscia), and for general information, see Kubitzki (2002d).

Synonymy: Huerteaceae Doweld

GERRARDINACEAE Alford  Back to Main Tree

Vessels?; petiole bundle arcuate, or three in an arc; mucilage cells in epidermis; leaves spiral, vein proceeding to glandular tooth, with a branch to the vein above; hypanthium +, C thin, small, stamens equal and opposite petals, disc +, G [2], unilocular, placentae apical, 2 ovules/carpel, style +, stigma?; fruit a berry, K persistent; seed with a fleshy outer layer, lignified ribbon-like cells inside; endosperm ?type, embryo minute; n = ?

1/2. Eastern Africa.

See Alford (2006) for what little is known about the family, description of venation modified. In addition, see G. eylesiana: stem anatomy, J. D. & E. G. Chapman 9242; leaf anatomy, Brass 16641; seed anatomy, Iversen et al. 85748; G. foliosa: stem and seed anatomy, Strey 11052; leaf anatomy, Hilliard & Burtt 6751.

Perrottetia   Back to Main Tree

Paratracheal parenchyma +; sclereids +; petiole bundle depressed annular with an adaxial inverted bundle and wing bundles, stomata ?anomocytic; leaves distichous (spiral); inflorescence thyrsoid; (flowers 4-8-merous), C small, disc +, G [2], 2 basal erect epi-apotropous intermediate ovules/carpel, micropyle endostomal, style short, single; fruit a berry, K + C persistent; testa thin-walled, ± fleshy, rodlike structures on inner tangential walls of endotesta, exotegmen palisade in T.S. [fibrous], ridged; endosperm ?type, embryo medium; n = ?

1/ca 15. China to Malesia and N.E. Australia, Mexico to Peru (Map: from Ding Hou 1962, New World rather approximate).

The flowers may be imperfect. There are idioblasts in the sepals with thickened inner tangential walls. The seeds lack an aril (Corner 1976; cf. Ding Hou 1962).

For general information, see Ding Hou (1962), for floral morphology, etc., see Matthews and Endress (2005b), for vegetative anatomy, see P. sessiliflora - Cogollo et al. 7294.

DIPENTODONTACEAE Merrill, nom. cons.   Back to Main Tree

Trees; petiole bundle arcuate; ?stomata; hairs uniseriate; leaves two-ranked, 2ndary veins pinnate, stipules lobed; inflorescence umbellate; flowers 5(-7)-merous; hypanthium short, spreading, K and C similar, valvate, basally connate, staminodial nectaries opposite petals, G [3], placentation axile basally, 2 [?kind] ovules/carpel borne on top of placenta, with a free central prolongation, style +, stigma punctate; fruit eventually ?septicidally dehiscent, K and C persistent; seed single, coat with palisade tissue [obliquely lying ribbon cells] underneath collapsed polygonal cells; endosperm ?type, embryo ?very short; n = ?

1[list]/1: Dipentodon sinicus. S. China and adjacent Burma, India and Vietnam (Map: from Yuan et al. 2008).

• Dipentodontaceae can be recognised by their two-ranked, serrate leaves and lobed stipules that are borne on the stem adjacent to the leaves. The simply umbellate inflorescences with small flowers and fruits that have almost indistinguishable and persistent sepals and petals are distinctive.

Mabberley (1997) described the leaves as being spiral. In the two flowers that I examined I could find only a single well-developed ovule.

Dipentodontaceae were included in Santalales by Cronquist (1981) because of apparent similarities in gynoecial structure, but the toothed leaf margin and large, lobed stipules suggested that this was incorrect. Dipentodonaceae were placed by Takhtajan (1997) in his Violales (= Malpighiales), while Wu et al. (2002, 2003) recognised a Dipentodontales C. Y. Wu et al. in Dilleniidae, where it was placed between Passiflorales (which included Caricaceae) and Violales (Cucurbitales were next).

For general information, see Merrill (1941), for pollen, see Lobreau-Callen (1982), and for floral morphology and a comparison with putatively related taxa, see Liu and Cheng (1991)..