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; shoot apical meristem complex; arbuscular mycorrhizae +; stem with ectophloic eustele, endodermis 0, xylem endarch; 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 ?; leaf vascular bundles collateral; leaves spiral, simple, axillary buds?, prophylls [including bracteoles] two, lateral; plant heterosporous, sporangia eusporangiate, on sporophylls, sporophylls aggregated in indeterminate cones/strobili; true pollen [microspores] +, mono[ana]sulcate, pollen exine and intine homogeneous, ovules unitegmic, crassinucellate, megaspore tetrad tetrahedral, only one megaspore develops, megasporangium indehiscent; male gametophyte development endo/exosporic, gametes two, with cell walls; 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, 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, numbers unstable, P not differentiated, outer members not enclosing the rest of the bud, A many, development centripetal, 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, endexine compact, lamellate only in the apertural regions, pollen tube elongated, with callose plugs, penetrating between cells, growth rate moderate, siphonogamy occuring, 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; pollen tectate-columellate, tectum reticulate [perforated]; 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.

EUDICOTS: Myricetin, delphinidin scattered, asarone 0 [unknown in some groups, + in some asterids]; root epidermis derived from root cap [?Buxaceae, etc.]; nodes 3:3; stomata anomocytic; flowers (dimerous), cyclic, K/outer P members with three traces, "C" with a single trace, few, (polyandry widespread), filaments fairly slender, anthers basifixed, pollen with endexine, tricolpate, G with complete postgenital fusion, style solid [?here]; seed coat?

THIS LOT (but getting fewer and fewer) UNPLACED  Main Tree, Synapomorphies.

Includes Brachynema, Haptanthaceae, Hoplestigmataceae, Medusandraceae.

Brachynema   Back to Unplaced

Evergreen tree; vessel elements with scalriform perforation plates; nodes ?5:5; cristarque cells +; sclereids and sclereid nests +, pericyclic fibers +; pith [and in petiole] with diaphragms; petiole bundle annular; stomata anisocytic, cyclocytic, etc.; hairs unicellular; leaves spiral, margin with glandular teeth, stipules 0; inflorescence ± fasciculate, bracts and bracteoles 0?; flowers 5-merous, K connate, C long-tubular, valvate, A adnate to base of C, connective produced, pollen porate, nectary 0, G [3-5], 1 apical pendulous ?epitropous ovule/loculus, style 0; fruit subdrupaceous, K accrescent; ?testa undistinguished; endosperm with some starch and a yellowish sticky substance, embryo small, apical; n = ?

1/2: Peru, Venezuela, Brasil; Amazonia. [Photo - Flower.]

• Brachynema has spirally-arranged leaves that are very unequal in size - particularly in petiole length, which varies from being about 20 cm to almost absent - in the one innovation and have glandular teeth, the petiole is pulvinate at both ends. The flowers are distinctive: the narrowly tubular corolla has valvate lobes and five stamens inserted at the base, and the spherical ovary has a sessile stigma. The connate calyx is accrescent in fruit, forming a cup under the single-seeded fruit; the seed is vertically channeled, vascular bundles running down the channels.

Baas et al. (1982: they examined Brachynema ramiflorum) recorded only infrequent and thin-walled sclereids. However, in the material examined there were numerous sclereid nests in the cortex, indeed, they sometimes formed an almost a continuous layer outside the pericycle, and stem, petiole, and also, judging from the way young leaves had dried, even the midrib had strongly sclerified diaphragms; the inside of the xylem cylinder was strongly fluted. Sleumer (1984) described the inflorescences as being ebracteate corymbs. The single, large seed is vertically channeled, with vascular bundles running down the channels; I presume these vascular bundles are pericarpial in nature. The seed coat is almost obliterated, and it is difficult to make out details of cell walls, etc. Sleumer (1984) described the endosperm as having amylum and fatty substances. The endosperm stains rather weakly for starch, and the cells contain yellowish globules, the "fatty" and "sticky" substances above.

Brachynema has recently often been associated with Olacaceae s.l. (Santalales), thus Lobreau-Callen (1980) placed it in Anacoloseae and Baas et al. (1982) placed it with Scorodocarpus in particular. It has also been linked with Ebenaceae (Ericales), as by Reed (1955) and others, while in a recent morphological phylogenetic analysis it appears close to Symplocaceae (Ericales; Malécot 2002). The stamens appear to alternate with the corolla members (see Sleumer 1984), rather unusual for Santalales, and indeed Brachynema has none of the more distinctive anatomical features of Santalales. Integument number - and indeed most details of embryology, development, and chemistry - are unknown.

For vegetative anatomy, see Baas et al. (1982), and for general information, see Sleumer (1984). Brachynema axillare: floral morphology, Rimachi Y. 4465, frout and vegetative anatomy, Lisener 16136.

HOPLESTIGMATACEAE Engler & Gilg   Back to Unplaced

Deciduous trees; cork superficial; vessel elements with simple perforations; nodes ?3:3; cuticle wax crystalloids 0?; stomata ?; buds perulate; leaves spiral, 2ndary veins pinnate, margins entire; inflorescences terminal, cymes scorpioid, bracts and bracteoles 0; K connate, splitting irregularly, C 11-14, basally connate, A 20-35, adnate to base of C, pollen colporate, nectary ?, G [2], placentation intrusive parietal, 2 pendulous unitegmic ovules/carpel, style short, branches long, bent outwards and then inwards, stigmas U-shaped, expanded; fruit a drupe, K persisting; seed coat ?; endosperm slight; n = ?

1[list]/2. W. Africa.

Hoplestigma perhaps belongs near Boraginaceae because of its scorpioid cymose inflorescence, absence of bracts, pollen with pseudocolpi (as in Bourreria and Ehretia - Nowicke & Miller 1989), and gynoecium - two carpels with parietal placentation, as in Hydrophyllaceae (see also Takhtajan 1997). Increase in number of floral parts - although not the gynoecium - in Boraginaceae s.l. is known from both Cordiodeae and Lennooideae as well as in Codon. Hoplestigmataceae were included in the Violales by Cronquist (1981), perhaps because of their parietal placentation. The embryology, etc., of the family are largely unknown. Both the petals and stamens are described as being in several series (Goldberg 1986).

MEDUSANDRACEAE Brenan, nom. cons.   Back to Unplaced

Tree; chemistry?; secretory canals +; cork superfifical; vessel elements with scalariform perforations; nodes ?; petiole bundle annular, including annular bundle; stomata anomocytic; hairs unicellular, lignified; leaves spiral, margins toothed, 2ndary veins palmate, 2 sides of the base meeting on top of the swollen petiole, stipules cauline; inflorescences racemose, flowers small, K open, C free, A = and opposite C, pollen ca 9 µm long, staminodes very long, opposite K, densely hairy, disc 0, G [(3) 4], placentation central, 6-8 apical epitropous ovules in total, styles separate, short, stigmas barely enlarged; fruit a capsule, K much enlarged; seed single, large, slightly ruminate, coat?; endosperm copious, embryo small; n = ?

1[list]/2. Tropical W. Africa.

• Medusandraceae are trees whose stipulate leaves have long petioles that are swollen at the apex and weakly serrate blades with strong veins arising from at or near the base. The axillary inflorescences are almost catkin-like, the flowers having long and conspicuous staminodes borne opposite the sepals. The fruit is single seeded and capsular, and the sepals are much accrescent, becoming strongly recurved.

Vascular pitting is scalariform, and the pits are bordered. Note that the leaves of Medusandra are probably simple, not unifoliate (cf. Brenan 1952; Hutchinson 1973); the rather swollen apex of the petiole is like that of many Euphorbiaceae, Hydnocarpus, Octoknema, etc., which are not usually described as being possibly unifoliolate. Petiole anatomy in the region of the pulvinus is complex.

For Soyauxia, mentioned here in previous versions, see Peridiscaceae (Saxifragales). Medusandraceae are associated with Passifloraceae by Soltis et al. (2005a), certainly, the serrate leaf blades and the cauline stipules suggest relationships other than to Santalales or Santalanae (cf. Cronquist 1981; Takhtajan 1997; Thorne 2007).

Details of anatomy are taken from Metcalfe (1952).

Synonymy: Medusandrales Brenan