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, 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, 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, distance to first ovule 1.1.-2.1 mm, 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 ?type, stylulus short, hollow, 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.

ASTERIDS - Sympetalae redux?: Nicotinic acid metabolised to its arabinosides; (iridoids +); tension wood decidedly uncommon; C sympetalous, if evident only early in development, petals free, anthers dorsifixed?, (nectary gynoecial), ovules unitegmic, integument thick, endothelium +, nucellar epidermis does not persist, style +, long; endosperm cellular, embryo long.

ERICALES [ASTERID I + II]: ovules tenuinucellate.

ASTERID I + II   Back to Main Tree

Ellagic acid 0, proanthocyanidins not common; inflorescence cymose; C forming a distinct tube, A epipetalous, = and opposite sepals or P.

This whole clade is notably speciose (Magallón & Sanderson 2001), although Garryales and Aquifoliales in particular are less so, indeed, in both the asterid I and II clades small clades with rather small flowers are sister to the remainder. The asterid I clade includes many large and monosymmetric-flowered taxa that have fruits with many seeds (but cf. Convolvulaceae, Lamiaceae, Verbenaceae); the apices of the petals tend to be rounded (but cf. Acanthaceae). The asterid II clade has many taxa with small flowers that are aggregated into conspicuous inflorescences and the fruits have few seeds (but cf. Campanulaceae, Goodeniaceae, etc.); the apices of the petals tend to be pointed.

There are relatively few cases of polyandry in the asterids, and these seem to be associated with considerable increases in the numbers of perianth parts, and sometimes also carpels, which then occur in a single whorl. Examples are some species of Schefflera (Plerandra s. str.) and Plerandra (both Araliaceae), Lamiaceae-Symphorematoideae, and also Codon, Hoplestigma, and Lennoa and relatives (all Boraginaceae s.l., but not immediately related). In Plerandra, at least, fasciation seems to have occured, and there are about as many stamens as carpels (Sokoloff et al. 2007b). Dialypetalanthus (Rubiaceae) also has more numerous stamens that would be expected, but how the flowers are constructed here is unclear. Polyandry in other eudicots usually occurs independently of any changes in sepal, petal or carpel number (but cf. Crassulaceae: stamens = carpels; Actinidia: many carpels in a single whorl), so there may be a change in floral organisation/development within the asterids. There may also be a change in chemistry, ellagic acid being notably uncommon in the [asterid I + II] clade.

Albach et al. (2001a, see also Soltis et al. 2005b) assign possession of iridoids to the base of the asterid clade. However, this feature is placed higher up the tree here, partly because of topological uncertainties, but partly because in Lamiales (for example), the four clades that are successively sister to the remaining Lamiales either lack iridoids or have iridoids different from those found in the other members of the clade (whether or not Carlemanniaceae have iridoids is unknown).

ASTERID I   Back to Main Tree

G [2]; loss of introns 18-23 in d copy of RPB2 gene.

This clade is called the lamiids by B. Bremer et al. (2002).

Although Garryales seem to be sister to the rest of the asterid I group, the composition of the order is unclear. Oncothecaceae have been considered close, but neither they nor the other families or genus groups mentioned immediately below link strongly to Garryales (e.g. Kårehed 2001; for the position of Oncothecaceae, see also Cameron 2001, 2003; Olmstead et al. 2000; B. Bremer et al. 2002). Pyrenacantha, Chlamydocarya, Sarcostigma, Iodes, and Icacina (Icacinaceae s. str.) form a clade in the rbcL tree of Savolainen et al. (2000b), although there placed (but with very little support) at the base of the rosids; these genera belong to Icacinaceae group III of Bailey and Howard (1941) and are included below in Icacinaceae s. str. There was initially only weak support for Icacinaceae in this position (D. Soltis et al. 2000), but Kårehed (2001) has identified four ex-Icacinaceous groups associated with Garryales, Icacinaceae s. s.tr, and the Cassinopsis, Emmotum and Apodytes groups. However, groupings within a more widely circumscribed Garryales could still not be identified, nor did the larger Garryales have any strong support. Relationships in the four genera of this part of Icacinaceae included in the analysis of B. Bremer et al. (2002) are also consistent with the classification adopted here, while the Bayesian analysis of Soltis et al. (2007: .99 pp) recovered Icacina as sister to all other asterid I taxa included. (Other genera that used to be included in Icacinaceae are placed in the asterid II group, i.e. in Aquifoliales [as Cardiopteridaceae, Stemonuraceae] and Apiales [as Pennantiaceae: see Kårehed 2001, 2003]).

Studies on the duplication of the RPB2 gene show that the I copy persists in most of the asterid I clade almost alone in the whole rosid/asterid group (see also discussion under Trochodendrales and at the beginning of the rosid group [Berberidopsidales]), as well as in Ericales. Based on the same pattern of retention, as well as the loss of introns 18-23 in the d copy in this group, Aquifoliaceae (and all? Aquifoliales) may also belong in the asterid I clade (Oxelman et al. 2004b). Since both Garrya and Eucommia have only the d copy, perhaps this is a feature of Garryales in particular, or part of them - sampling needs to be improved, and optimisation of the persistence/loss of the I copy on the asterid tree will probably be difficult. In a parsimony analysis of combined molecular and morphological data Lens et al. (2008a) found [Oncothecaceae + unassigned ex-Icacinaceae] (72% bootstrap) to be sister to the asterid I clade, but with little support, while in a Bayesian analysis the first clade was joined by Garryales (but little support for the enlarged clade) as sister to other asterid I groups (1.0 p.p.).

For literature on Icacinaceae in the old sense, which may refer to any and all of these groups, see Bailey and Howard (1941: anatomy), Fagerlind (1945: embryology), Heintzelmann and Howard (1948), Padmanabhan (1961: embryology), Sleumer (1971a: general), van Staveren and Baas (1973: epidermis), Baas (1973: epidermis, 1974: stomata), Lobreau-Callen (1980: pollen), Kaplan et al. (1991: chemistry), and Teo and Haron (1999: anatomy). Kårehed (2001, 2002b) discusses the taxa in their current circumscriptions, while Lens et al. (2008a) provide a detailed anatomical survey in a phylogenetic context.

Unplaced: note, all have valvate corollas, 1-2 apical ovules/carpel and drupaceous fruits; morphologically, it would be easy to include them in an expanded Garryales.

Included: Icacinaceae, Metteniusaceae, Oncothecaceae, and assorted unassigned genera.   Back to Main Tree

Oncothecaceae + Metteniusaceae: nodes 5:5; petiole bundles arcuate, complex; A basifixed, G [5], 2 ovules/carpel; fruit a drupe; endosperm copious.

ONCOTHECACEAE Airy Shaw   Back to Unplaced

Tree; chemistry?; plant glabrous; cork cambium outer cortical; phloem stratified; vessel elements with scalariform perforation plates; nodes also 3:3; astrosclereids +; plant glabrous; leaf "convolute", margin with caducous glands, petiole short; inflorescences axillary, branched; flowers small, K ± free, C ?aestivation, A extrorse, anthers bisporangiate/monothecal, disc?, G opposite petals, ovules apical, campylotropous (1), funicle long, styles separate, conduplicate, stigma punctate; stone several-seeded, K persistent; seed coat ?; embryo terete, cotyledons short; n = 25.

1[list]/2. New Caledonia.

Oncothecaceae are embryologically unknown. The stomata, perhaps modified paracytic, are distinctive. Oncotheca macrocarpa, recently described (McPherson et al. 1991), has stamens quite unlike those of O. balansae; the incurved, pointed connective of stamens of the latter species is responsible for the generic name.

The family was included in Theales by Cronquist (1981) and Takhtajan (1997).

Some information is taken from Baas (1975), Carpenter (1975) and Carpenter and Dickison (1976); the latter described the stamens as being opposite the petals, but drew them as being opposite the sepals.

Synonymy: Oncothecales Doweld

METTENIUSACEAE Schnizlein   Back to Unplaced

Evergreen trees; cork?; vessel elements with simple perforation plates; nodes 5:5; petiole bundles several, arcuate, complex; stomata anomo-cyclocytic; mesophyll fibers +; hairs ± T-shaped; leaves ?, margins entire; inflorescence cymose/thyrsiform; K short, quincuncial, C valvate, late corolla tube formation, contorted, anthers moniliform, the 4 sporangial series [i.e. vertical rows of locellae] dehiscing individually, disc 0, 4 carpels very much reduced, barely evident, ovules pendulous, style long, stigma punctate; fruit 1-seeded, asymmetrically ridged; seed coat thin, vascularised; embryo curved; n = ?

1/7. Costa Rica, Panama and N.W. South America (Map: from Lozano C. & Lozano 1988). [Photo - Flower]

The flowers of Metteniusa suggest Cornales s. str., but its ovary is superior. In morphological analyses Metteniusa fits quite comfortably into Cardiopteridaceae, ex Icacinaceae (Kårehed 2001, Cornaceae were not included). However, molecular analyses suggest a position in this general area (asterid I), and petiole anatomy, carpel number, etc., are similar to Oncothecaceae in particular (González & Rudall 2007, which see for much information); I have summarized characters assuming this relationship.

For general information, see Lozano C. and Lozano (1988).

ICACINACEAE Miers, nom. cons.   Back to Unplaced

Trees or lianes (with non-axillary branch tendrils); (plants Al-accumulators); monoterpene indole alkaloid camptothecin +, iridoids ?; secondary thickening often atypical [included phloem often +, etc.]; vessel elements with simple perforation plates; banded and/or vasicentric axial parenchyma; (crystal sand in wood rays); phloem stratified; nodes 1:1; (medullary bundles + - Iodes), petiole bundles arcuate and wing or annular (and medullary); stomata cyclocytic (anomocytic), hairs unicellular, often adpressed and ± T-shaped, also globular; leaves spiral (opposite), conduplicate(-plicate), margins entire (toothed; palmately lobed; 2ndary veins palmate); plant dioecious[?], inflorescence branched, spicate or racemose, pedicels articulated; (flowers 4-merous); K connate (0 – Pyrenacantha; ± free - Phytocrene), (C free), valvate, (adaxially keeled), apices narrow and inflexed, disc 0 (+): staminate flowers: A dorsifixed (epipetalous), pollen also porate, echinate, pistillode +; carpellate flowers: staminodes +/0, G also 1?, 2 (apically bitegmic?) tenuinucellate ovules/carpel, funicular obturator +, style + and stigma punctate, or style 0 and stigma broad; fruit a 1-seeded drupe, flattened and/or ribbed or not, (endocarp cells papillate; endosperm ruminate), K persistent; seed coat?, no testa bundles; endosperm copious to 0, chalazal haustorium + [Notapodytes], starchy [only Merrilliodendron?], embryo usu. long, cotyledons foliaceous; n = 10, 12.

24(?25)[list of genera in Icacinaceae in the old sense]/149(150): Iodes (28). Pantropical, inc. W. Pacific, to China and Japan (Map: Sleumer 1971a; Utteridge & Brummitt 2007).

• Icacinaceae s. str. are undistinguished vegetatively, having exstipulate and usually entire leaves; a number are vines and these may have opposite leaves and branch tendrils that are not strictly axillary. The flowers are small, with a connate corolla and an at most rather short and slender style. Their single-seeded, drupaceous fruits are longer than broad and often flattened and/or ribbed.

Hoseia, with its long-petiolate leaves that have palmate venation and long-dentate margins, is particularly distinctive vegetatively. Note that the description above largely refers to the Icacina group (see Kårehed 2001). The family is very poorly known embryologically.

For other ex-Icacinaceae, apart from those mentioned immediately below, see the asterid II Aquifoliales (Cardiopteridaceae, Stemonuraceae) and Apiales (Pennantiaceae).

For the indole alkaloid camptothecin, see Lorence and Nessler (2004). It may be derived from secologanin.

For additional information, see Utteridge et al. (2005: general) and Rankin et al. (2008) and Pigg et al. (2008), both fruit anatomy, esp. of fossils.

Synonymy: Phytocrenaceae R. Brown, Pleurisanthaceae van Tieghem, Sarcostigmataceae van Tieghem - Icacinales van Tieghem - Icacinanae Doweld

Apodytes - 2/7: Old World tropics, to Australia (Queensland) (Map: from Sleumer 1971a)- vessel elements with simple [Rhaphiostylis] or scalariform perforation plates; bordered pits +; xylem parenchyma various; nodes 1:1, 3:3; stomata anomocytic (cyclocytic); leaves spiral or two-ranked; fruit very asymmetrical, ribbed, style thin, persistent; n = 20, ?22. For fruit morphology, see Potgeiter et al. (1994b).

Cassinopsis - 1/4: Africa and Madagascar – vessel elements with scalariform perforation plates; nodes 3:3; stomata cyclocytic; hairs not ± T-shaped; leaves opposite. For fruit morphology, see Potgeiter et al. (1994a).

Emmotum (Emmotaceae van Tieghem) - 4(?6)/21(32): Central and South America, West Indies, rarely Malesia (Map: from Sleumer 1971a) – vessel elements with scalariform perforation plates; bordered pits +; diffuse apotracheal parenchyma +; nodes 3:3; stomata cyclocytic(-anomocytic), (Platea; leaves ± conduplicate in bud) G [3], 2 ovules/carpel; fruit flattened and symmetrical. Perhaps includes Calatola – scalariform perforation plates; nodes 3:3; leaves toothed, conduplicate, Cordia growth pattern.

Synonymy: Emmotales Doweld

For other information, see Bailey and Howard (1941, their group II: anatomy), Fagerlind (1945: embryology), Heintzelmann and Howard (1948), Padmanabhan (1961: embryology), Sleumer (1971a: general), van Staveren and Baas (1973: epidermis), Baas (1973: epidermis, 1974: stomata), Lobreau-Callen (1980: pollen), Kaplan et al. (1991: chemistry), and Teo and Haron (1999: anatomy). Kårehed (2001, 2002c) discusses the taxa in their current circumscriptions. The wood occasionally fluoresces.

GARRYALES Lindley   Main Tree, Synapomorphies.

Woody; route II decarboxylated iridoids [inc. aucubin], gutta +; vessel elements with scalariform perforation plates; fibers with bordered pits; nodes?; petiole bundles arcuate; sclereids +; stomata?; hairs unicellular; plants dioecious; flowers small; C valvate, free, anthers basifixed, pollen ± atectate, ovary 1-celled, 1-2 apical crassinucellate apotropous ovules/carpel, style at most short; fertilization delayed; fruit indehiscent. - 2 families, 3 genera, 18 species.

The order is narrowly circumscribed (see above). In all three genera there is a lengthy period (11 days to four weeks) between pollination ands fertilization (Sogo & Tobe 2006); it would be interesting to examine Icacinaceae and related genera and Oncothecaceae from this point of view.

Much work is needed on basic embryology, etc.; Eucommiaceae may lack endothelium, but data are lacking for the other taxa. The nucellus is thin, even if the ovules are crassinucellate. Although the iridoid aucubin is found in both families, it is not unique to them; neither family can synthesize catalpol (Grayer et al. 1999).

Includes Eucommiaceae, Garryaceae.

Synonymy: Eucommiales Cronquist - Eucommianae Reveal

GARRYACEAE Lindley, nom. cons.   Back to Garryales

Evergreen shrubs or trees; tannins 0, petroselenic and chlorogenic acid +; rays at least 10 cells wide, with square or upright cells; nodes 3:3; crystal sand +; cuticle waxes as tubules (and platelets); stomata paracytic; hairs with counter-clockwise ridges; leaves opposite, ± connate basally, conduplicate; inflorescence terminal; flowers 4-merous; staminate flowers: A not epipetalous; carpellate flowers: G [(3)], inferior, 1 ovule/carpel, large placental obturator +; fruit a berry; testa thick, outer part sarcotestal, inner part with cells elongated tangentially; endosperm nuclear, with hemicellulose, embryo short.

2[list]/17. W. North America, Central America and the Greater Antilles (Garrya) and Sikkim to N. Burma, China and Taiwan to Japan (Aucuba) (Map: from Dahling 1978).[Photo - Fruit]

Garrya

Diterpenoid alkaloids +; fibers with helical thickening; leaf margins cartilaginous; inflorescences catkinate, main axis racemose, bracts ± connate; staminate flowers: P [?= C] valvate, connate apically, A alternate with P, (pollen colporate, partly tectate); carpellate flowers: P [= K] 2, minute, or 0, integument 20-25 cells thick, styles separate, spreading, stigmatic much of their length; testa multiplicative, exotestal cells large, palisade, fleshy; suspensor very long, endosperm green, starchy; n = 11.

1/13. W. North America, Antilles.

For discussion of the flowers of Garrya, in which both K or C may be absent when mature, see Baillon (1877), Hallock (1930) and Eyde (1964); Baillon provides perhaps the only report of minute sepals being visible in the very young flower. Liston (2003) has recently suggested that staminate flowers may have a vestigial disc (not a superior ovary, as has been suggested). Eyde (1964) described the ovules as being tenuinucellate, while others (e. g. Hallock 1930; Kapil & Mohana Rao 1967) describe and illustrate them as being crassinucellate. The calyx is much reduced in staminate flowers, but the corolla is more reduced than the calyx in carpellate flowers; in the latter, the bracteoles may be adnate to the ovary and appear to represent the calyx!

For additional information, see Liston (2006).

Aucuba

Gutta percha ?, flavonols, kaempferol +; vascular tracheids present; cauline pericyclic sheath 0; leaves serrate; K minute or 0; staminate flowers: pollen?; carpellate flowers: staminodes 0, nectary on top of G, (several megasporocytes), style +, stigma subcapitate, bilobed; n = 8.

1/4. East Asia.

Aucuba shows early corolla tube formation (Reidt & Leins 1994). Van Tieghem (1898) described the three outer layers of the integument as persisting in the fruit.

For chemical information, see Iwashina et al. (1997), for general information, see Horne (1914).

Synonymy: Aucubaceae J. Agardh

• Garryaceae are evergreen, woody plants that can be recognised by their exstipulate, opposite leaves that are basally connate, flowers with an inferior ovary and only one whorl of the perianth well developed, and baccate fruits.

The apparent dissimilarity of Garrya and Aucuba masks extensive similarity, and the two can be intergrafted quite readily (Horne 1914: note that Ilex and Buxus could also be intergrafted, but the graft did not really take - see also Pinaceae and Portulacaceae).

For wood anatomy, see Noshiro and Baas (1998).

EUCOMMIACEAE Engler, nom. cons.   Back to Garryales

Deciduous trees; O-methylated flavonols, little oxalate accumulation, inulin +, tanniniferous; hairs micropapillate; plant with articulated laticifers, producing gutta; vessel elements with simple perforations; true tracheids +; tracheid/tracheid pits circular, bordered; sieve tube/cell plastids with starch grains; phloem fibers +; nodes 1:1; cuticle wax crystalloids 0; stomata anomocytic; buds perulate; leaves spiral, supervolute-curved, margins toothed; flowers axillary, bracteoles 0, P 0; staminate flowers: A 5-12, filaments short, connective prolonged; carpellate flowers: one G aborts, 2 ovules/carpel, micropyle long [700-1000 µm long], nucellar cap +, stigmas spreading, decurrent; fruit a samara; seed 1, testa thin; endosperm copious, ?embryo; n = 17.

1[list]/1: Eucommia ulmoides. Central China (Map: from Fu & Hong 2000; Wang et al. 2003).

• The family can be recognised vegetatively by its strongly serrate, spirally arranged, exstipulate leaves; when the lamina is pulled apart, the two halves are held together by threads of gutta. The flowers, with their two, spreading, decurrent stigmas and the samara fruits, are rather like those of an elm (Ulmaceae), but there is no perianth.

Eucommia fossils are known to occur widely in the North Temperate region (Wang et al. 2003).

Although chalazogamy appears not to occur here, some pollen tubes may grow towards the chalaza; more than one tube may proceed down the lengthy micropyle (Sogo & Tobe 2006c).

The teeth have glandular apices, and associated veins approach them (Hickey & Wolfe 1975). Cullen (1978) described the leaf ptyxis as being involute.

Although Eucommia has often been associated with Euptelea (see Ranunculales), the chemistry and ovule of the former are consistent with a position in the asterids.

For embryology, etc., see Zhang et al. (1990).