LIGNOPHYTA

True roots +; lateral meristems: cork cambium producing cork abaxially, vascular cambium producing phloem abaxially and xylem adaxially.

EXTANT SEED PLANTS/SPERMATOPHYTA

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 derived from (some) sinapyl and particularly coniferyl alcohols, thus containing p-hydroxyphenyl and guaiacyl lignin units, (lignins derived from p-coumaryl alcohol, i.e. S [syringyl] lignin units); true roots present, apex multicellular, xylem exarch, and 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 and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, plastids with starch grains; phloem fibres +; stem cork cambium superficial, root cork cambium deep seated; leaves with single trace from sympodium ["nodes 1:1"]; stomata ?; leaf vascular bundles collateral; leaves megaphyllous [determinancy evolved first, then ad/abaxial symmetry], spiral, simple, lamina with vein density up to 5 mm/mm² [mean for all non-angiosperms 1.8]; axillary buds associated with at most some leaves; prophylls [including bracteoles] two, lateral; 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, developing after pollination, 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 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.

MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, non-hydrolysable tannins, quercetin and/or kaempferol +, 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; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, with gelatinous fibres; 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 cells from same mother cell that gave rise to the sieve tube; sugar transport in phloem passive; nodes unilacunar [1:?]; stomata with ends of guard cells level with pore, paracytic, outer stomatal ledges producing vestibule; leaves petiolate, lamina [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; most/all leaves with axillary buds; flowers perfect, pedicellate, polysymmetric, parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P not sharply differentiated, with a single trace, outer members not enclosing the rest of the bud, often smaller than inner members; 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 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, 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, stylulus short, hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, 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, megaspore tetrad linear, functional megaspore chalazal, lacking sporopollenin and cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; P deciduous in fruit; seed exotestal; pollen binucleate at dispersal, trinucleate eventually, germinating in less than 3 hours, pollination siphonogamous, tube elongated, growing at 80-600 µm/hour, with pectic outer wall, callose inner wall and callose plugs, growing between cells, penetration of ovules via micropyle [porogamous] within ca 18 hours, distance to first ovule 1.1.-2.1 mm, tube moves between nucellar cells; double fertilisation +, endosperm diploid, cellular [micropylar and chalazal domains develop diffently, 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 cellular ab initio, minute; germination hypogeal, seedlings/young plants sympodial; Arabidopsis-type telomeres [(TTTAGGG)_n]; whole genome duplication, 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]].

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. This is because some taxa basal to the [magnoliid + monocot + eudicot] group have been surprisingly little studied, there is considerable homoplasy as well as variation within and between families of the ANITA grade 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... For other features such as details of sugar transport in the phloem, their placement on the tree is frankly speculative. Finally, for features such as parietal tissue/a nucellus only one (Nymphaeales) to three cells thick above the embryo sac and a stylar canal lacking an epidermal layer, although plesiomorphous for basal grade angiosperms (Williams 2009), I am unsure where on the tree a thicker nucellus and a stylar epidermal layer are acquired.

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

[HUERTEALES [MALVALES + BRASSICALES]]: ?

Evolution.

Evolution. Divergence & Distribution. The age of the stem of this clade was estimated as (102-)96(-90) and (80-)76(-72) million years (two penalized likelihood dates); Bayesian relaxed clock estimates were similar to the first estimate (Wang et al. 2009), while Magallón and Castillo (2009) estimated ages of ca 98.1 and 98.4 million years for relaxed and constrained penalized likelihood datings.

HUERTEALES Doweld  Main Tree, Synapomorphies.

Vessel elements with scalariform perforation plates; mucilage cells +; lamina margins toothed, stipules cauline; inflorescence cymose; flowers small, short hypanthium +, stamens = and opposite sepals; G [2], ovary unilocular; fruit a berry; exotegmen rather massive, of more or less strongly laterally-compressed fibres; endosperm +, embryo at most medium. - 4 families, 6 genera, 24 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, but I have tentatively suggested that exotegmic seeds are a synapomorphy for the clade, although seeds of taxa like Gerrardina (pers. obs.) and Petenaea need developmental studies. 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 that Huerteales (Perrottetia not included), Brassicales and Malvales formed a polytomy, 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 between the two genera, despite this they do not appear to be sister taxa (Worberg et al. 2009). Petenaea has recently been found to be rather weakly (bootstrap) associated with Gerrardina, and in general bootstrap values for relationships are low, even if posterior probabilities are higher (Christenhusz et al. 2010). Relationships within the order seem to be [[Gerrardinaceae + Petenaeaceae] [Tapisciaceae + Dipentodontaceae]], although Dipentodon is sister to Tapisciaceae in some analyses (Worberg et al. 2009).

Classification. Like Crossosomatales, Huerteales are accumulating several small families; when the clade is better known, rationalization (= reduction in number) may be in order - we hardly know enough so say whether or not the families are similar other than in gross phenetic terms.

Includes Dipentodontaceae, Gerrardinaceae, Petenaeaceae, Tapisciaceae.

Synonymy: Dipentodontales C. Y. Wu et al.

[Gerrardinaceae + Petenaeaceae]: ?

GERRARDINACEAE M. H. Alford  Back to Main Tree

Vessel elements with scalariform perforation plates; petiole bundle arcuate, or three in an arc; mucilage cells in epidermis; leaves spiral, lamina toothed, with vein proceeding to glandular tooth and with a branch to the vein above; C clawed, thin, small; stamens equal and opposite petals; nectary cupular; placentae apical, stigma?; seed with a fleshy outer layer, lignified laterally-compressed 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 from that source. Christenhusz et al. (2010) describe the wood anatomy of young stems. 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.

PETENAEACEAE Christenhusz, M. F. Fay & M. W. Chase   Back to Main Tree

Vessels in radial multiples; leaves spiral, lamina venation palmate, stipules +; P valvate, with adaxial moniliform hairs and basal glands; P +; A 8-12; nectary +; G [5], placentae pendent, style long; ovules many; berry lobed, with a persistent style; n = ?

1/1: Petenaea cordata. Central America (map: from Christenhusz et al. 2010).

• Petenaea is a distinctive plant with its spirally-arranged and palmately-nerved closely serrate leaves; its flowers are borne in branched inflorescences and the adaxial surface of the single perianth whorl is densely covered by pink, beaded hairs.

Chemistry, Morphology, etc. For the wood anatomy of Petenaea, see also Kukachka (1962). The genus is described as having minute stipules (Bayer 2002). For some general information, see Christenhusz et al. (2010).

Previous Relationships. Petenaea has previously been linked with Tiliaceae and Elaeaocarpaceae (Mabberley 2009), Bayer et al. (1999, but sampling) had suggested on molecular data that it might be associated with Malvales, being tentatively associated with Muntingiaceae (see also A.P.G. 2003).

[Tapisciaceae + Dipentodontaceae]: wood parenchyma 0.

TAPISCIACEAE Takhtajan  Back to Main Tree

Wood fluorescing; fibres 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, style hollow, apically branched or styles ± separate, stigma?; ovule 1/carpel, basal, apotropous, hypostase +; (fruit a drupe); testa thin-walled, (mesotesta sclerotic), chalaza ballooning into endosperm; endosperm ?type, embryo medium, coyledons flat; 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. Divergence & Distribution. 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. 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 Corner (1976: seed anatomy), Carlquist and Hoekman (1985: wood anatomy), Dickison (1986a: 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 (but see Corner 1976 for differences in seed coat and 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 in fruit.

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, ovules borne on top of placenta, with a free-central prolongation, stigma punctate; ?ovule morphology; fruit eventlaterally-compressedually ?septicidally dehiscent from the base upwards, ?funicle much enlarged; seed single; coat with obliquely-lying lignified ribbon cells, collapsed polygonal cells underneath; 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 (anisocytic); leaves distichous (spiral); inflorescence thyrsoid; (flowers 4-8-merous); ovary septate, style short, single; ovules basal, erect, epi-apotropous; seed arillate [Yang et al.]; testa thin-walled, ± fleshy, inner tangential walls of endotesta with rod-like structures, exotegmen 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 in each.

For general information on Perrottetia, see Ding Hou (1962), for seed coat, see Corner (1976), for floral morphology, etc., see Matthews and Endress (2005b: also mucilage cells!), for mostly stomatal morphology, see den Hartog and Baas (1978), 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).

Previous relationships. Dipentodontaceae were included in Santalales by Cronquist (1981) because of apparent similarities in gynoecial structure, but the toothed lamina margin and large, lobed stipules suggested that this was incorrect. They 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).