EMBRYOPSIDA Pirani & Prado

Gametophyte dominant, independent, multicellular, thalloid, with single-celled apical meristem, showing gravitropism; rhizoids +, unicellular; acquisition of phenylalanine lysase [PAL], phenylpropanoid metabolism [lignans +, flavonoids + (absorbtion of UV radiation)], xyloglucans +; plant [protoplasm dessication tolerant], ectohydrous [free water outside plant physiologically important]; cuticle +; cell wall also with (1->3),(1->4)-ß-D-MLGs [Mixed-Linkage Glucans]; chloroplasts per cell, lacking pyrenoids; glycolate metabolism in leaf peroxisomes [glyoxysomes]; centrioles in vegetative cells 0, metaphase spindle anastral, predictive preprophase band of microtubules, phragmoplast + [cell wall deposition spreading from around the spindle fibres], plasmodesmata +; antheridia and archegonia jacketed, stalked; spermatogenous cells monoplastidic; blepharoplast, bicentriole pair develops de novo in spermatogenous cell, associated with basal bodies of cilia [= flagellum], multilayered structure [4 layers: L1, L4, tubules; L2, L3, short vertical lamellae] + spline [tubules from L1 encircling spermatid], basal body 200-250 nm long, associated with amorphous electron-dense material, microtubules in basal end lacking symmetry, stellate array of filaments in transition zone extended, axonemal cap 0 [microtubules disorganized at apex of cilium]; male gametes [spermatozoids] with a left-handed coil, cilia 2, lateral; oogamy; sporophyte dependent on gametophyte, embryo initially surrounded by haploid gametophytic tissue, plane of first division horizontal [with respect to long axis of archegonium/embryo sac], suspensor/foot +, cell walls with nacreous thickenings; sporophyte multicellular, with at least transient apical cell [?level], sporangium +, single, dehiscence longitudinal; meiosis sporic, monoplastidic, microtubule organizing centre associated with plastid, cytokinesis simultaneous, preceding nuclear division, sporocytes 4-lobed, with a quadripolar microtubule system; spores in tetrads, sporopollenin in the spore wall, initially laid down in association with several trilamellar layers [white-line centred layers, i.e. walls multilamellate]; nuclear genome size <1.4 pg, LEAFY gene present, ethylene involved in cell elongation; chloroplast genome with close association between trnLUAA and trnFGAA genes.

Many of the bolded characters in the characterization above are apomorphies of subsets of streptophytes along the lineage leading to the embryophytes, not apomorphies of crown-group embryophytes per se.

All groups below are crown groups, nearly all are extant. Characters mentioned are those of the immediate common ancestor of the group, [] contains explanatory material, () features common in clade, exact status unclear.

STOMATOPHYTES

Abscisic acid, ?D-methionine +; sporangium with tapetal layer, columella + [developing from endothecial cells], seta developing from basal meristem [between epibasal and hypobasal cells; stomata +, anomocytic, cell lineage that produces them with symmetric divisions [perigenous]; underlying similarities in the development of conducting tissue and in rhizoids/root hairs; spores trilete; polar transport of auxins and class 1 KNOX genes expressed in the sporangium alone; shoot meristem patterning gene families expressed; MIKC, MI*K*C* and class 1 and 2 KNOX genes, post-transcriptional editing of chloroplast genes; gain of three group II mitochondrial introns.

[Anthocerophyta + Polysporangiophyta]: archegonia embedded/sunken in the gametophyte; sporophyte long-lived, chlorophyllous; sporophyte-gametophyte junction interdigitate, sporophyte cells showing rhizoid-like behaviour.

POLYSPORANGIOPHYTA†

Sporophyte branched, branching apical, dichotomous; sporangia several, each opening independently; spore walls not multilamellate [?here].

EXTANT TRACHEOPHYTA / VASCULAR PLANTS

Photosynthetic red light response; plant homoiohydrous [water content of protoplasm relatively stable]; control of leaf hydration passive; (condensed or nonhydrolyzable tannins/proanthocyanidins +); sporophyte soon independent, dominant, with basipetal polar auxin transport; lignins +; vascular tissue +sieve cells + [nucleus degenerating], tracheids +, in both protoxylem and metaxylem, plant endohydrous [physiologically important free water inside plant]; endodermis +; stem with an apical cell; branching dichotomous; leaves spirally arranged, blades with mean venation density 1.8 mm/mm2 [to 5 mm/mm2]; sporangia adaxial on the sporophyll, derived from periclinal divisions of several epidermal cells, wall multilayered [eusporangium]; columella 0; tapetum glandular; gametophytes exosporic, green, photosynthetic; basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; placenta with single layer of transfer cells in both sporophytic and gametophytic generations, root lateral with respect to the longitudinal axis of the embryo [plant homorhizic].

[MONILOPHYTA + LIGNOPHYTA]

Sporophyte branching ± indeterminate; root apex multicellular, root cap +, lateral roots +, endogenous; endomycorrhizal associations + [with Glomeromycota]; G-type tracheids +, with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangia borne in pairs and grouped in terminal trusses, dehiscence longitudinal, a single slit; cells polyplastidic, microtubule organizing centres not associated with plastids, diffuse, perinuclear; blepharoplasts +, paired, with electron-dense material, centrioles on periphery, male gametes multiciliate; chloroplast long single copy ca 30kb inversion [from psbM to ycf2]; LITTLE ZIPPER proteins.

LIGNOPHYTA†

Sporophyte woody; lateral root origin from the pericycle; branching lateral, meristems axillary; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].

SEED PLANTS†

Plants heterosporous; megasporangium surrounded by cupule [i.e. ovule +, cupule = integument]; pollen lands on ovule; megaspore germination endosporic [female gametophyte initially retained on the plant].

EXTANT SEED PLANTS / SPERMATOPHYTA

Plant 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 particularly with guaiacyl and p-hydroxyphenyl [G + H] units [sinapyl units uncommon, no Maüle reaction]; root stele with xylem and phloem originating on alternate radii, cork cambium deep seated; shoot apical meristem interface specific plasmodesmatal network; stem with vascular cylinder around central pith [eustele], phloem abaxial [ectophloic], endodermis 0, xylem endarch [development centrifugal]; wood homoxylous, tracheids and rays alone, tracheid/tracheid pits circular, bordered; mature sieve tube/cell lacking functioning nucleus, sieve tube plastids with starch grains; phloem fibres +; cork cambium superficial; leaves with single trace from vascular sympodium [nodes 1:1]; stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; axillary buds exogenous, (none; not associated with all leaves); prophylls two, lateral; leaves with petiole and lamina, development basipetal, blade simple; plant heterosporous, sporangia borne on sporophylls, sporophylls spiral; microsporophylls aggregated in indeterminate cones/strobili; grains monosulcate, aperture in ana- position [distal], primexine + [involved in exine pattern formation and deposition of sporopollenin from tapetum], exine and intine homogeneous; megasporangium indehiscent; ovules unitegmic, parietal tissue 2+ cells across, megaspore tetrad linear, functional megaspore single, chalazal, sporopollenin 0; gametophytes dependent on sporophyte, apical cell 0, rhizoids 0; male gametophyte development initially endosporic, tube developing from distal end of grain, gametes two, developing after pollination, with cell walls; female gametophyte initially syncytial, walls then surrounding individual nuclei; embryo cellular ab initio, endoscopic, plane of first cleavage of zygote transverse, suspensor +, short-minute, embryonic axis straight [shoot and root at opposite ends; plant allorhizic], cotyledons 2; plastid transmission maternal; ycf2 gene in inverted repeat, whole nuclear genome duplication [zeta duplication], 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.

ANGIOSPERMAE / MAGNOLIOPHYTA

Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANITA grade?], lignin also with syringyl units common [G + S lignin, positive Maüle reaction - syringyl:guaiacyl ratio more than 2-2.5:1], 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, hypodermis suberised and with Casparian strip [= exodermis +]; shoot apex with tunica-corpus construction, tunica 2-layered; reaction wood ?, associated gelatinous fibres [g-fibres] with innermost layer of secondary cell wall rich in cellulose and poor in lignin; 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 cell and sieve tube from same mother cell; sugar transport in phloem passive; nodes 1:?; stomata brachyparacytic [ends of subsidiary cells level with ends of pore], outer stomatal ledges producing vestibule, reduction in stomatal conductance to increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, venation hierarchical-reticulate, secondary veins pinnate, veins (1.7-)4.1(-5.7) mm/mm2, endings free; most/all leaves with axillary buds; flowers perfect, pedicellate, ± haplomorphic; protogynous; parts spiral [esp. the A], free, numbers unstable, development in general centripetal; P +, members each with a single trace, outer members not sharply differentiated from the others, not enclosing the floral bud; A many, filament not sharply distinguished from anther, stout, broad, with a single trace, anther introrse, tetrasporangiate, sporangia in two groups of two [dithecal], sporangium pairs dehiscing longitudinally by a common slit, ± embedded in the filament, walls with at least outer secondary parietal cells dividing, endothecium +, endothecial cells elongated at right angles to long axis of anther; (tapetum glandular), cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine lamellate only in the apertural regions, thin, compact; nectary 0; carpels present, superior, free, several, ascidiate, with postgenital occlusion by secretion, stylulus at most short [shorter than ovary], hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, stigma wet, extragynoecial compitum +; 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, functional megaspore, chalazal, lacking cuticle; female gametophyte four-celled [one module, nucleus of egg cell sister to one of the polar nuclei]; ovule not increasing in size between pollination and fertilization; pollen grains land on stigma, bicellular at dispersal, mature male gametophyte tricellular, germinating in less than 3 hours, pollen tube elongated, unbranched, growing between cells, growth rate (20-)80-20,000 µm/hour, apex of pectins, wall with callose, lumen with callose plugs, penetration of ovules via micropyle [porogamous], whole process takes ca 18 hours, distance to first ovule 1.1-2.1 mm; male gametes lacking cell walls, cilia 0, siphonogamy; double fertilization +, ovules aborting unless fertilized; P deciduous in fruit; mature seed much larger than ovule when fertilized, small [], dry [no sarcotesta], exotestal; endosperm diploid, cellular, heteropolar [micropylar and chalazal domains develop differently, 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; dark reversal Pfr → Pr; Arabidopsis-type telomeres [(TTTAGGG)n]; nuclear genome size <1.4 pg [1 pg = 109 base pairs], whole nuclear genome duplication [epsilon duplication]; protoplasm dessication tolerant [plant poikilohydric]; 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]].

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

[AUSTROBAILEYALES [[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]]]: vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood +; tectum reticulate; anther wall with outer secondary parietal cell layer dividing; carpels plicate; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.

[[CHLORANTHALES + MAGNOLIIDS] [MONOCOTS [CERATOPHYLLALES + EUDICOTS]]] / MESANGIOSPERMAE: benzylisoquinoline alkaloids +; sesquiterpene synthase subfamily a [TPS-a] [?level], polyacetate derived anthraquinones + [?level]; outer epidermal walls of root elongation zone with cellulose fibrils oriented transverse to root axis; P more or less whorled, 3-merous [possible position]; pollen tube growth intra-gynoecial [extragynoecial compitum 0]; embryo sac bipolar, 8 nucleate, antipodal cells persisting; endosperm triploid.

[MONOCOTS [CERATOPHYLLALES + EUDICOTS]]: (extra-floral nectaries +); (veins in lamina often 7-17 mm/mm2 or more [mean for eudicots 8.0]); (stamens opposite [two whorls of] P); (pollen tube growth fast).

[CERATOPHYLLALES + EUDICOTS]: ethereal oils 0.

EUDICOTS: (Myricetin, delphinidin +), asarone 0 [unknown in some groups, + in some asterids]; root epidermis derived from root cap [?Buxaceae, etc.]; (vessel elements with simple perforation plates in primary xylem); nodes 3:3; stomata anomocytic; flowers (dimerous), cyclic; protandry common; K/outer P members with three traces, ("C" +, with a single trace); A few, (polyandry widespread, initial primordia 5, 10, or ring, ± centrifugal), filaments fairly slender, anthers basifixed; microsporogenesis simultaneous, pollen tricolpate, apertures in pairs at six points of the young tetrad [Fischer's rule], cleavage centripetal, wall with endexine; G with complete postgenital fusion, stylulus/style solid [?here]; seed coat?

[PROTEALES [TROCHODENDRALES [BUXALES + CORE EUDICOTS]]]: (axial/receptacular nectary +).

[TROCHODENDRALES [BUXALES + CORE EUDICOTS]]: benzylisoquinoline alkaloids 0; euAP3 + TM6 genes [duplication of paleoAP3 gene: B class], mitochondrial rps2 gene lost.

[BUXALES + CORE EUDICOTS]: ?

CORE EUDICOTS / GUNNERIDAE: (ellagic and gallic acids +); leaf margins serrate; compitum + [one place]; micropyle?; whole nuclear genome duplication [palaeohexaploidy, gamma triplication], PI-dB motif +, small deletion in the 18S ribosomal DNA common.

[ROSIDS ET AL. + ASTERIDS ET AL.] / PENTAPETALAE: root apical meristem closed; (cyanogenesis also via [iso]leucine, valine and phenylalanine pathways); flowers rather stereotyped: 5-merous, parts whorled; P = calyx + corolla, the calyx enclosing the flower in bud, sepals with three or more traces, petals with a single trace; stamens = 2x K/C, in two whorls, internal/adaxial to the corolla whorl, alternating, (numerous, but then usually fasciculate and/or centrifugal); pollen tricolporate; G [5], G [3] also common, when [G 2], carpels superposed, compitum +, placentation axile, style +, stigma not decurrent; endosperm nuclear; fruit dry, dehiscent, loculicidal [when a capsule]; RNase-based gametophytic incompatibility system present; floral nectaries with CRABSCLAW expression; (monosymmetric flowers with adaxial/dorsal CYC expression).

[SANTALALES [BERBERIDOPSIDALES [CARYOPHYLLALES + ASTERIDS]]] / ASTERIDS ET AL. / SUPERASTERIDS : ?

[BERBERIDOPSIDALES [CARYOPHYLLALES + ASTERIDS]]: ?

[CARYOPHYLLALES + ASTERIDS]: seed exotestal; embryo long.

ASTERIDS / ASTERIDAE / ASTERANAE Takhtajan: nicotinic acid metabolised to its arabinosides; (iridoids +); tension wood decidedly uncommon; C enclosing A and G in bud, (connate [sometimes evident only early in development, petals then appearing to be free]); anthers dorsifixed?; (nectary gynoecial); G [2], style single, long; ovules unitegmic, integument thick, endothelium +, nucellar epidermis does not persist; exotestal [!: even when a single integument] cells lignified, esp. on anticlinal and/or inner periclinal walls; endosperm cellular.

[ERICALES [ASTERID I + ASTERID II]]: (ovules lacking parietal tissue) [tenuinucellate].

[ASTERID I + ASTERID II] / CORE ASTERIDS / EUASTERIDS: plants woody; ellagic acid 0, non-hydrolysable tannins not common; vessel elements with scalariform perforation plates; sugar transport in phloem active; inflorescence basically cymose; flowers rather small; C free, valvate, apex inflexed; A free, (if numerous, usu. associated with increased numbers of C or G), introrse; (pollen with orbicules); G [2], ?superposed, style short[?]; ovules 2/carpel, apical; fruit a drupe; seed single; duplication of the PI gene.

ASTERID I / LAMIIDAE: loss of introns 18-23 in d copy of RPB2 gene.

[METTENIUSALES [GARRYALES [GENTIANALES [[VAHLIACEAE + SOLANALES] [BORAGINALES + LAMIALES]]]]: ?

[GARRYALES [GENTIANALES [[VAHLIACEAE + SOLANALES] [BORAGINALES + LAMIALES]]]]: G [2], superposed; loss of introns 18-23 in RPB2 d copy

Age. The age of this node is estimated to be (121-)112(-103) m.y. (Janssens et al. 2009), (80-)76(-71) m.y. (Moore et al. 2010: 95% HPD), 124 m.y. (Z. Wu et al. 2014), or ca 104.5 m.y. (Nylinder et al. 2012: suppl.).

Phylogeny. For the relationships of Garryales, see the lamiid clade.

GARRYALES Martius   Main Tree.

Woody; route II decarboxylated iridoids [inc. aucubin], gutta +; vessel elements with helical thickenings; fibres with bordered pits; petiole bundles arcuate; sclereids +; stomata?; hairs unicellular; plants dioecious; flowers small; C free; anthers basifixed; pollen ± atectate; ovary 1-celled, styles branched to the base, spreading, stigmatic much of their length; ovule 1/carpel, apotropous, parietal tissue 3< cells across, endothelium 0; fertilization delayed; loss of RPB2 I copyy. - 2 families, 3 genera, 18 species.

Age. Lemaire et al. (2011b) date crown-group Garryales to (91-)63(-31) m.y., Bell et al. (96-)77, 70(-51) m.y., while Wikström et al. (2001) estimated it at (89-)84, 80(-75) m.y. and Naumann et al. (2013) at ca 65.9 m.y.; 67.9 m.y. is the estimate in Nylinder et al. (2012: suppl.) but about 43.5 m.y. in Magallón et al. (2015).

Note: (....) denotes a feature common in the clade, exact status uncertain, [....] includes explanatory material. Possible apomorphies are in bold. However, the actual level at which many of these features, particularly the more cryptic ones, should be assigned is unclear. This is partly because many characters show considerable homoplasy, in addition, basic information for all too many is very incomplete, frequently coming from taxa well embedded in the clade of interest and so making the position of any putative apomorphy uncertain. Then there is the not-so-trivial issue of how ancestral states are reconstructed (see above).

Evolution. Pollination Biology & Seed Dispersal. In all three genera there is a lengthy period (11 days to four weeks) between pollination and fertilization (Sogo & Tobe 2006); it would be interesting to examine Metteniusaceae and Icacinaceae from this point of view.

Chemistry, Morphology, etc. Although the iridoid aucubin is found in both families, it is not unique to them; neither family can synthesize catalpol (Grayer et al. 1999). For a summary of some anatomical variation in the family, see Lens et al. (2008a); the vessel elements are fairly short whether they have simple or scalariform plates.

The nucellus on the sides of the embryo sac is not very thick, even if the ovules have parietal tissue 3-8 cells across at the apex.

Much work is needed on basic embryology, etc., in Garryales.

Phylogeny. For the circumscription and relationships of Garryales, see the euasterids.

Includes Eucommiaceae, Garryaceae.

Synonymy: Aucubales Takhtajan, Eucommiales Cronquist

GARRYACEAE Lindley, nom. cons.   Back to Garryales

Garryaceae

Evergreen shrubs or trees; tannins 0, petroselenic and chlorogenic acids +; vessel elements with scalariform perforation plates; rays at least 10 cells wide, with square or upright cells; also crystal sand +; cuticle waxes as tubules (and platelets); stomata paracytic; hairs with counter-clockwise ridges; leaves opposite, ± connate basally, lamina vernation conduplicate; inflorescence terminal; flowers 4-merous; staminate flowers: A not adnate to C, pistillode +; carpellate flowers: staminodes 0; ovary inferior; ovule 1/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, the Greater Antilles and East Asia.

Age. Magallón and Castillo (2009) suggest that crown-group Garryaceae are some 49.8 m.y.o., Wikström et al. (2001) date them to (57-)52, 42(-37) m.y., Janssens et al. (2009) to 20±8.6 m.y. and Bell et al. (2010) to (58-)38, 36(-17) m.y. ago.

1. Garrya Lindley

Diterpenoid alkaloids +; fibres with helical thickening; lamina cartilaginous, margins ± entire; inflorescences catkinate, bracts ± connate; staminate flowers: P [?= bracteoles] valvate, connate apically; A alternating with P; (pollen colporate, partly tectate); nectary 0; pistillode +; carpellate flowers: P [?= K] 2, minute, or 0; [G (3)]; ovules epitropous, integument 12-30 cells across, endothelium 0, parietal tissue 4-5 cells thick, (nucellar cap 2 cells across), hypostase +, funicle quite long, with "collar" below the ovule; antipodals persistent or not; seeds 2, not flattened, testa multiplicative, exotestal cells large, palisade, fleshy, most of testa not persistent; suspensor very long, endosperm ?green, starchy; n = 11.

1/13. W. North America, Central America and the Greater Antilles (see map above: New World, from Dahling 1978). [Photo - Fruit.]

2. Aucuba Thunberg

Gutta percha ?, flavonols, kaempferol +; vascular tracheids present; pericyclic fibres 0; lamina margins serrate; K minute or 0, C with early tube formation, valvate, apex incurved; staminate flowers: pollen?; carpellate flowers: G 1 (2), stylulus +, stigma capitate to shortly decurrent, bilobed; nectary on top of G; integument "thick", parietal tissue ca 8 cells across, (nucellar cap 2 cells across), endothelium?; (megaspore mother cells several); ?seed coat; n = 8.

1/4. Sikkim to N. Burma, China and Taiwan to Japan (see map above: Asia).

Synonymy: Aucubaceae Berchtold & J. Presl

Evolution. Divergence & Distribution. Fossil leaves of Aucuba are reported from the Eocene of Washington (Wehr & Hopkins 1994).

Chemistry, Biology, etc. For discussion of the flowers of Garrya, in which both calyx and corolla 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 carpellate flower. The calyx is reported to be 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 then appear to be sepals. Liston (2003) thought that the staminate flowers had a vestigial disc, rather than a superior ovary, as had been suggested. More work on floral development is needed.

There seems to be disagreement over details of the embryology of Garrya. Thus Eyde (1964) described the ovules as being tenuinucellate, while Hallock (1930) and Kapil and Mohana Rao 1967) described and illustrated them as having a very thick parietal layer. For some details of the ovule of Aucuba, see Palm and Rutgers (1917); they noted (p. 121) that the parietal tissue kept on dividing, forming a "mighty cap on the embryosac". There are sometimes two ovules (Horne 1914) - does this imply that there are two carpels?

For additional general information, see Dahling (1978: Garrya), for chemical information, see Iwashina et al. (1997), for wood anatomy, see Moseley and Beeks (1955: Garrya) and Noshiro and Baas (1998: both genera), for inflorescence morphology, esp. of Garrya, see Jahnke (1986), for some floral morphology of Aucuba, see Reidt and Leins (1994), and for some general floral information, see Horne (1914).

Classification. The apparent dissimilarity of Garrya and Aucuba masks extensive similarities, and the two can be intergrafted quite readily (Horne 1914). The two families are combined (see A.P.G. 2009).

Previous Relationships. The relationships of Garrya in particular have been a bit of an enigma: Moseley and Beeks (1955) compared its wood anatomy with that of taxa that are here placed in 12 separate orders, mostly rosids. Aucuba was placed in Cornaceae by Cronquist (1981), Garryaceae were separate, but near by, while Takhtajan (1997) placed Garryaceae and Aucubaceae in separate, but adjacent, orders.

EUCOMMIACEAE Engler, nom. cons.   Back to Garryales

Eucommiaceae

Trees, deciduous; O-methylated flavonols, little oxalate accumulation, inulin +, tanniniferous; laticifers +, articulated; vessel elements with simple perforation plates; true tracheids and rays alone, tracheid/tracheid pits circular, bordered; phloem fibres +; nodes 1:1; hairs micropapillate; cuticle wax crystalloids 0; stomata anomocytic; buds perulate; leaves spiral, lamina vernation supervolute-curved, margins toothed; flowers axillary, bracteoles 0; P 0; staminate flowers: A 4-12, filaments short, connective prolonged; endothecium biseriate; tapetal cells 2-6-nucleate; pistillode 0; carpellate flowers: staminodes 0; one carpel aborts; ovule integument 5-9 cells across, micropyle long [700-1000 µm long], parietal tissue 3-5 cells across, nucellar cap ca 3 cells across; archesporium multicellular; fruit a samara, seed 1, flattened; testa thin; endosperm copious, embryo long; n = 17; chloroplast ORF184 lost.

1[list]/1: Eucommia ulmoides. Central China (map: from Guo 2000; Wang et al. 2003; green crosses are fossil distribution, approximate only, mostly from Ferguson et al. 1997).

Evolution. Divergence & Distribution. Eucommia fossils occur widely in the North Temperate region from the Palaeocene onwards, being found as far south as central Mexico (Call & Dilcher 1997; Y.-F. Wang et al. 2003; Manchester et al. 2009).

Pollination Biology & Seed Dispersal. Whether chalazogamy occurs in Eucommia is unclear. Sogo and Tobe (2006c) noted that some pollen tubes grew towards the chalaza and more than one tube could proceed down the lengthy micropyle, but Eckardt (1963) did record chalazogamy; the pollen tube is also sometimes branched.

Chemistry, Morphology, etc. The teeth of the lamina have glandular apices, and associated veins approach them (Hickey & Wolfe 1975). Cullen (1978) described the leaf vernation as being involute. The lateral nucellar tissue is thin, ca 2 cells across, and the tissue above the embryo sac is relatively much more prominent (Eckardt 1963).

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

Previous Relationships. Eucommia has often been associated with Euptelea (see Ranunculales), as in Cronquist (1981), but the chemistry and ovule of the former are consistent with a position in the asterids.