EXTANT SEED PLANTS

Plant woody, 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 rich in guaiacyl units; true roots present, apex multicellular, xylem exarch, branching endogenous; arbuscular mycorrhizae +; shoot apical meristem multicellular, interface specific plasmodesmatal network; 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 mm/mm² [mean for all non-angiosperms 1.8]; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores, i.e. no distal pore for release of gametes] +, 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 [N/O//A/C and P//BE lines], 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 in 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 a sieve plate and cytoplasm with P-proteins, companion cells from same mother cell that gave rise to the sieve tube; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves with petiole and lamina [the latter formed from the primordial leaf apex], development of venation acropetal, 2ndary veins pinnate, fine venation reticulate, veins (1.7-)4.1(-5.7) mm/mm², endings free; flowers perfect, polysymmetric, parts spiral [esp. the A], free, development in general centripetal, numbers unstable; P not sharply differentiated, outer members not enclosing the rest of the bud, smaller than inner members; 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, walls developing by centripetal furrowing; pollen subspherical, binucleate at dispersal, trinucleate eventually, tectum continuous or microperforate, ektexine columellar, endexine thin, compact, lamellate only in the apertural regions; nectary 0; G free, several, ascidiate, with postgenital occlusion by secretion, few [?1] ovules/carpel, ovules marginal, anatropous, bitegmic, [outer integument often largely subdermal in origin, inner integument dermal], micropyle endostomal, integuments 2-3 cells thick, megasporocyte single, megaspore lacking sporopollenin and cuticle, chalazal, female gametophyte four-celled [one-modular, nucleus of egg cell sister to one of the polar nuclei], stylulus short, hollow, stigma ± decurrent, dry [not secretory]; P deciduous in fruit; seed exotestal; 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, distance to first ovule 1.1.-2.1 mm; 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, minute; 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 + C/PHYB + E gene pairs.

Evolution. Possible apomorphies for flowering plants 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, there is considerable variation between families in particular for several of these characters, and also because details of relationships among gymnosperms will affect the level at which some of these characters are pegged. For example, if reticulate-perforate pollen is optimized to the next node on the tree (see Friis et al. 2009 for a discussion), it effectively makes the pollen morphology of the common ancestor of all angiosperms ambiguous....

NYMPHAEALES [AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessels +, elements with scalariform perforation plates, axial parenchyma diffuse or diffuse-in-aggregate; tectum reticulate-perforate [here?]; ?genome duplication; "DEAER" motif in AP3 and PI genes lost, gaps in these genes.

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

ROSIDS: embryo long; genome duplication; chloroplast infA gene defunct, mitochondrial coxII.i3 intron 0.

MALVIDAE  Back to Main Tree

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

ROSIDS: embryo long; genome duplication; chloroplast infA gene defunct, mitochondrial coxII.i3 intron 0.

MALVIDAE = [[GERANIALES + MYRTALES] [CROSSOSOMATALES [PICRAMNIALES [SAPINDALES [HUERTEALES [MALVALES + BRASSICALES]]]]]]: ?

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

PICRAMNIALES [SAPINDALES [HUERTEALES [MALVALES + BRASSICALES]]]: 2 apical pendulous ovules/carpel.

SAPINDALES [HUERTEALES [MALVALES + BRASSICALES]]: flavonols +; vessel elements with simple perforation plates; (cambium storied); petiole bundle(s) annular; inner integument thicker than outer, style +; endosperm scanty.

HUERTEALES [MALVALES + BRASSICALES]: ?

HUERTEALES Doweld  Main Tree, Synapomorphies.

Vessel elements with scalariform perforation plates; mucilage cells +; leaf margins toothed, stipules cauline; inflorescence cymose; flowers small, short hypanthium +, stamens = and opposite sepals; G [2], ovary unilocular; endosperm +, embryo at most medium. - 3 families, 5 genera, 23 species.

Chemistry, Morphology, etc. The morphology, anatomy, and secondary chemistry of the whole group are badly in need of detailed investigation. Overall, the flowers of Huerteales seem to be rather similar, although there is variation in androecial position in particular. The mechanical (lignified) layer of the seed may differ in its origin within the order (pers. obs.). Worberg et al. (2009) summarize what is known about this group, and information in their summary is slightly emended below; see also Yang et al. (2009) for chromosome numbers.

Phylogeny. For the association of the Tapisciaceae and Dipentodontaceae, see Peng et al. (2003), also James Horn (pers. comm.). Perrottetia was 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 Huerteales (Perrottetia not included), Brassicales and Malvales formed a polychotomy, the combined group being rather poorly supported as sister to Sapindales. Gerrardina eylesiana shows a possibly superficial but still striking similarity to Perrottetia in particular, and perhaps there is a similarity in seed coat anatomy of the two genera, however, they do not appear to be sister taxa (Worberg et al. 2009). Relationships within the order seem to be [Gerrardinaceae [Tapisciaceae + Dipentodontaceae]], although Dipentodon is sister to Tapisciaceae in some analyses (Worberg et al. 2009).

Includes Dipentodontaceae, Gerrardinaceae, Tapisciaceae.

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

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; C clawed, thin, small, stamens equal and opposite petals, placentae apical, stigma?; fruit a berry, K persistent; seed with a fleshy outer layer, lignified ribbon-like cells inside; endosperm ?type, embryo minute; n = ?

1[list]/2. Eastern and southern Africa (map: data from GBIF, vii.2009).

Chemistry, Morphology, etc. Gerrardina foliosa appears to have clawed petals and three sepals larger than the others (ToL, vii.2009). See Alford (2006) for what little is known about the family; the description of the venation is 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.

Previous Relationships. Gerrardina has previously been included in Flacourtiaceae.

Tapisciaceae + Dipentodontaceae: wood parenchyma 0.

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, inflexed - Huertea), pollen colpate, (disc 0); G septate or not, 1 basal apotropous 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, 15.

2[list]/5. China (Tapiscia sinensis), West Indies and N. South America (map: from Ying et al. 1993; GBIF and TROPICOS vii.2009; fossils [blue] from Manchester 1988). [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.

Evolution. The distinctive fruits of Tapiscia are known from the Eocene onwards in Europe, and somewhat later in North America (Manchester 1988; Manchester et al. 2009 and references).

Chemistry, Morphology, etc. 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, the receptacle also becoming inflated and suberised (Liu et al. 2008; Teng & Liu 2009).

See Carlquist and Hoekman (1985: wood anatomy), 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).

Previous Relationships. 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).

Synonymy: Huerteaceae Doweld

DIPENTODONTACEAE Merrill, nom. cons.   Back to Main Tree

Trees; K and C similar, K ± valvate, micropyle endostomal [Perrottetia]; K + C persistent.

2/[list]16. Southeast Asia to Malesia, Mexico to Peru.

Dipentodon Dunn

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 valvate, basally connate; staminodial nectaries opposite petals; G [3], placentation axile basally, [?kind] ovules borne on top of placenta, with a free central prolongation, stigma punctate; fruit eventually ?septicidally dehiscent; seed single, coat with palisade tissue [obliquely lying ribbon cells] underneath collapsed polygonal cells; endosperm ?type, embryo ?very short; n = 17.

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

Perrottetia Kunth

(Vessel elements simple); 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); ovary septate, ovules basal, erect, style short, single; ovules epi-apotropous; fruit a berry; seed arillate [Yang et al.]; testa thin-walled, ± fleshy, rodlike structures on inner tangential walls of endotesta, exotegmen palisade in T.S. [fibrous], ridged; endosperm ?type, embryo medium; n = 10.

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

Chemistry, Morphology, etc. The flowers of Perrottetia may be imperfect. It has idioblasts in the sepals with thickened inner tangential walls, and the seeds lack an aril (Corner 1976; cf. Ding Hou 1962). Mabberley (1997) described the leaves of Dipentodon as being spiral. In the two flowers that I examined I could find only a single well-developed ovule.

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

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).