EMBRYOPSIDA Pirani & Prado
Gametophyte dominant, independent, multicellular, initially ±globular, not motile, branched; showing gravitropism; glycolate oxidase +, glycolate metabolism in leaf peroxisomes [glyoxysomes], acquisition of phenylalanine lysase* [PAL], flavonoid synthesis*, microbial terpene synthase-like genes +, triterpenoids produced by CYP716 enzymes, CYP73 and phenylpropanoid metabolism [development of phenolic network], xyloglucans in primary cell wall, side chains charged; plant poikilohydrous [protoplasm dessication tolerant], ectohydrous [free water outside plant physiologically important]; thalloid, leafy, with single-celled apical meristem, tissues little differentiated, rhizoids +, unicellular; chloroplasts several per cell, pyrenoids 0; centrioles/centrosomes in vegetative cells 0, microtubules with γ-tubulin along their lengths [?here], interphase microtubules form hoop-like system; metaphase spindle anastral, predictive preprophase band + [with microtubules and F-actin; where new cell wall will form], phragmoplast + [cell wall deposition centrifugal, from around the anaphase spindle], plasmodesmata +; antheridia and archegonia +, jacketed*, surficial; blepharoplast +, centrioles develop de novo, bicentriole pair coaxial, separate at midpoint, centrioles rotate, associated with basal bodies of cilia, multilayered structure + [4 layers: L1, L4, tubules; L2, L3, short vertical lamellae] (0), 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, asymmetrical; oogamy; sporophyte +*, multicellular, growth 3-dimensional*, cuticle +*, plane of first cell division transverse [with respect to long axis of archegonium/embryo sac], sporangium and upper part of seta developing from epibasal cell [towards the archegonial neck, exoscopic], with at least transient apical cell [?level], initially surrounded by and dependent on gametophyte, placental transfer cells +, in both sporophyte and gametophyte, wall ingrowths develop early; suspensor/foot +, cells at foot tip somewhat haustorial; sporangium +, single, terminal, dehiscence longitudinal; meiosis sporic, monoplastidic, MTOC [= MicroTubule Organizing Centre] associated with plastid, sporocytes 4-lobed, cytokinesis simultaneous, preceding nuclear division, quadripolar microtubule system +; wall development both centripetal and centrifugal, 1000 spores/sporangium, sporopollenin in the spore wall* laid down in association with trilamellar layers [white-line centred lamellae; tripartite lamellae]; plastid transmission maternal; nuclear genome [1C] <1.4 pg, main telomere sequence motif TTTAGGG, KNOX1 and KNOX2 [duplication] and LEAFY genes present, ethylene involved in cell elongation; chloroplast genome with close association between trnLUAA and trnFGAA genes [precursors for starch synthesis], tufA, minD, minE genes moved to nucleus; mitochondrial trnS(gcu) and trnN(guu) genes +.
Many of the bolded characters in the characterization above are apomorphies of more or less inclusive clades 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.
Sporophyte well developed, branched, branching dichotomous, potentially indeterminate; hydroids +; stomata on stem; sporangia several, terminal; spore walls not multilamellate [?here].
II. TRACHEOPHYTA / VASCULAR PLANTS
Sporophyte long lived, cells polyplastidic, photosynthetic red light response, stomata open in response to blue light; plant homoiohydrous [water content of protoplasm relatively stable]; control of leaf hydration passive; plant endohydrous [physiologically important free water inside plant]; PIN[auxin efflux facilitators]-mediated polar auxin transport; (condensed or nonhydrolyzable tannins/proanthocyanidins +); borate cross-linked rhamnogalactan II, xyloglucans with side chains uncharged [?level], in secondary walls of vascular and mechanical tissue; lignins +; roots +, often ≤1 mm across, root hairs and root cap +; stem apex multicellular [several apical initials, no tunica], with cytohistochemical zonation, plasmodesmata formation based on cell lineage; vascular development acropetal, tracheids +, in both protoxylem and metaxylem, G- and S-types; sieve cells + [nucleus degenerating]; endodermis +; stomata numerous, involved in gas exchange; leaves +, vascularized, spirally arranged, blades with mean venation density ca 1.8 mm/mm2 [to 5 mm/mm2], all epidermal cells with chloroplasts; sporangia in strobili, sporangia adaxial, columella 0; tapetum glandular; sporophyte-gametophyte junction lacking dead gametophytic cells, mucilage, ?position of transfer cells; MTOCs not associated with plastids, basal body 350-550 nm long, stellate array in transition region initially joining microtubule triplets; archegonia embedded/sunken [only neck protruding]; embryo suspensor +, shoot apex developing away from micropyle/archegonial neck [from hypobasal cell, endoscopic], root lateral with respect to the longitudinal axis of the embryo [plant homorhizic].[MONILOPHYTA + LIGNOPHYTA]
Sporophyte growth ± monopodial, branching spiral; roots endomycorrhizal [with Glomeromycota], lateral roots +, endogenous; G-type tracheids +, with scalariform-bordered pits; leaves with apical/marginal growth, venation development basipetal, growth determinate; sporangium dehiscence by a single longitudinal slit; cells polyplastidic, MTOCs diffuse, perinuclear, migratory; blepharoplasts +, paired, with electron-dense material, centrioles on periphery, male gametes multiciliate; nuclear genome [1C] 7.6-10 pg [mode]; chloroplast long single copy ca 30kb inversion [from psbM to ycf2]; mitochondrion with loss of 4 genes, absence of numerous group II introns; LITTLE ZIPPER proteins.
Sporophyte woody; stem branching axillary, buds exogenous; lateral root origin from the pericycle; cork cambium + [producing cork abaxially], vascular cambium bifacial [producing phloem abaxially and xylem adaxially].
SEED PLANTS† / SPERMATOPHYTA†
Growth of plant bipolar [plumule/stem and radicle/root independent, roots positively geotropic]; plants heterosporous; megasporangium surrounded by cupule [i.e. = unitegmic ovule, cupule = integument]; pollen lands on ovule; megaspore germination endosporic, female gametophyte initially retained on the plant, free-nuclear/syncytial to start with, walls then coming to surround the individual nuclei, process proceeding centripetally.
EXTANT SEED PLANTS
Plant evergreen; nicotinic acid metabolised to trigonelline, (cyanogenesis via tyrosine pathway); microbial terpene synthase-like genes 0; primary cell walls rich in xyloglucans and/or glucomannans, 25-30% pectin [Type I walls]; lignin chains started by monolignol dimerization [resinols common], particularly with guaiacyl and p-hydroxyphenyl [G + H] units [sinapyl units uncommon, no Maüle reaction]; roots often ≥1 mm across, stele diarch to pentarch, xylem and phloem originating on alternating radii, cork cambium deep seated, gravitropism response fast; stem apical meristem complex [with quiescent centre, etc.], plasmodesma density in SAM 1.6-6.2[mean]/μm2 [interface-specific plasmodesmatal network]; eustele +, protoxylem endarch, endodermis 0; 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; leaf nodes 1:1, a single trace leaving the vascular sympodium; leaf vascular bundles amphicribral; guard cells the only epidermal cells with chloroplasts, stomatal pore with active opening in response to leaf hydration, control by abscisic acid, metabolic regulation of water use efficiency, etc.; branching by axillary buds, exogenous; prophylls two, lateral; leaves with petiole and lamina, development basipetal, lamina simple; sporangia borne on sporophylls; spores not dormant; microsporophylls aggregated in indeterminate cones/strobili; grains monosulcate, aperture in ana- position [distal], primexine + [involved in exine pattern formation with deposition of sporopollenin from tapetum there], exine and intine homogeneous, exine alveolar/honeycomb; ovules with parietal tissue [= crassinucellate], megaspore tetrad linear, functional megaspore single, chalazal, sporopollenin 0; gametophyte ± wholly dependent on sporophyte, development initially endosporic [apical cell 0, rhizoids 0, etc.]; male gametophyte with tube developing from distal end of grain, male gametes two, developing after pollination, with cell walls; embryo cellular ab initio, suspensor short-minute, embryonic axis straight [shoot and root at opposite ends], primary root/radicle produces taproot [= allorhizic], cotyledons 2; embryo ± dormant; chloroplast ycf2 gene in inverted repeat, trans splicing of five mitochondrial group II introns, rpl6 gene absent; ??whole nuclear genome duplication [ζ/zeta duplication event], 2C genome size (0.71-)1.99(-5.49) pg, two copies of LEAFY gene, PHY gene duplications [three - [BP [A/N + C/O]] - copies], 5.8S and 5S rDNA in separate clusters.
IID. ANGIOSPERMAE / MAGNOLIOPHYTA
Lignans, O-methyl flavonols, dihydroflavonols, triterpenoid oleanane, apigenin and/or luteolin scattered, [cyanogenesis in ANA 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 cap meristem closed (open); pith relatively inconspicuous, lateral roots initiated immediately to the side of [when diarch] or opposite xylem poles; epidermis probably originating 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; starch grains simple; primary cell wall mostly with pectic polysaccharides, poor in mannans; tracheid:tracheid [end wall] plates with scalariform pitting, multiseriate rays +, wood parenchyma +; sieve tubes enucleate, sieve plates with pores (0.1-)0.5-10< µm across, cytoplasm with P-proteins, not occluding pores of plate, companion cell and sieve tube from same mother cell; ?phloem loading/sugar transport; nodes 1:?; dark reversal Pfr → Pr; protoplasm dessication tolerant [plant poikilohydric]; stomata randomly oriented, brachyparacytic [ends of subsidiary cells ± level with ends of guard cells], outer stomatal ledges producing vestibule, reduction in stomatal conductance with increasing CO2 concentration; lamina formed from the primordial leaf apex, margins toothed, development of venation acropetal, overall growth ± diffuse, secondary veins pinnate, fine venation hierarchical-reticulate, (1.7-)4.1(-5.7) mm/mm2, vein endings free; flowers perfect, pedicellate, ± haplomorphic, protogynous; parts free, numbers variable, development centripetal; P = T, petal-like, 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], each theca dehiscing longitudinally by a common slit, ± embedded in the filament, walls with at least outer secondary parietal cells dividing, endothecium +, cells elongated at right angles to long axis of anther; tapetal cells binucleate; microspore mother cells in a block, microsporogenesis successive, walls developing by centripetal furrowing; pollen subspherical, tectum continuous or microperforate, ektexine columellate, endexine restricted to the apertural regions, thin, compact, intine in apertural areas thick, orbicules +, pollenkitt +; nectary 0; carpels present, superior, free, several, spiral, ascidiate [postgenital occlusion by secretion], stylulus at most short [shorter than ovary], hollow, cavity not lined by distinct epidermal layer, stigma ± decurrent, carinal, dry; suprastylar 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, nucellar cap?; megasporocyte single, hypodermal, functional megaspore lacking cuticle; female gametophyte lacking chlorophyll, four-celled [one module, egg and polar nuclei sisters]; ovule not increasing in size between pollination and fertilization; pollen grains bicellular at dispersal, germinating in less than 3 hours, siphonogamy, pollen tube unbranched, growing towards the ovule, between cells, growth rate (ca 10-)80-20,000 µm h-1, tube 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 gametophytes tricellular, gametes 2, lacking cell walls, ciliae 0, double fertilization +, ovules aborting unless fertilized; fruit indehiscent, P deciduous; mature seed much larger than fertilized ovule, small [<5 mm long], dry [no sarcotesta], exotestal; endosperm +, ?diploid [one polar nucleus + male gamete], cellular, development heteropolar [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 short [<¼ length of seed]; plastid and mitochondrial transmission maternal; Arabidopsis-type telomeres [(TTTAGGG)n]; nuclear genome [2C] (0.57-)1.45(-3.71) [1 pg = 109 base pairs], ??whole nuclear genome duplication [ε/epsilon event]; 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, palaeo AP3 and PI genes [paralogous B-class genes] +, with "DEAER" motif, SEP3/LOFSEP and three copies of the PHY gene, [PHYB [PHYA + PHYC]]; chloroplast IR expansions, chlB, -L, -N, trnP-GGG genes 0.
[NYMPHAEALES [AUSTROBAILEYALES [MONOCOTS [[CHLORANTHALES + MAGNOLIIDS] [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 [MONOCOTS [[CHLORANTHALES + MAGNOLIIDS] [CERATOPHYLLALES + EUDICOTS]]]]: phloem loading passive, via symplast, plasmodesmata numerous; vessel elements with scalariform perforation plates in primary xylem; essential oils in specialized cells [lamina and P ± pellucid-punctate]; tension wood + [reaction wood: with gelatinous fibres, G-fibres, on adaxial side of branch/stem junction]; anther wall with outer secondary parietal cell layer dividing; tectum reticulate; nucellar cap + [character lost where in eudicots?]; 12BP [4 amino acids] deletion in P1 gene.
[MONOCOTS [[CHLORANTHALES + MAGNOLIIDS] [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 [?here]; pollen tube growth intra-gynoecial; extragynoecial compitum 0; carpels plicate [?here]; embryo sac monosporic [spore chalazal], 8-celled, bipolar [Polygonum type], antipodal cells persisting; endosperm triploid.
[CERATOPHYLLALES + EUDICOTS]: ethereal oils 0 [or next node up]; fruit dry [very labile].
EUDICOTS: (Myricetin +), 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 ?, 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], short [<2 x length of ovary]; seed coat?; palaeotetraploidy event.
[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]: mitochondrial rps11 gene lost.
CORE EUDICOTS / GUNNERIDAE: (ellagic and gallic acids +); leaf margins serrate; compitum + [one position]; micropyle?; γ genome duplication [allopolyploidy, 4x x 2x], x = 3 x 7 = 21, 2C genome size (0.79-)1.05(-1.41) pg, 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 = K + C, K enclosing the flower in bud, with three or more traces, C with single trace; A = 2x K/C, in two whorls, internal/adaxial to C, alternating, (numerous, but then usually fasciculate and/or centrifugal); pollen tricolporate; G [(3, 4) 5], whorled, placentation axile, style +, stigma not decurrent, compitum + [another position]; endosperm nuclear/coenocytic; fruit dry, dehiscent, loculicidal [when a capsule]; floral nectaries with CRABSCLAW expression.
[SANTALALES [BERBERIDOPSIDALES [CARYOPHYLLALES + ASTERIDAE]]] / ASTERIDS ET AL. / SUPERASTERIDS : ?
[BERBERIDOPSIDALES [CARYOPHYLLALES + ASTERIDAE]]: ?
[CARYOPHYLLALES + ASTERIDAE]: seed exotestal; embryo long.
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?; if nectary +, gynoecial; G , style single, long; ovules unitegmic, integument thick [5-8 cells across], 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 [LAMIIDAE/ASTERID I + CAMPANULIDAE/ASTERID II]]: ovules lacking parietal tissue [= tenuinucellate] (present).
[LAMIIDAE/ASTERID I + CAMPANULIDAE/ASTERID II] / CORE ASTERIDS / EUASTERIDS / GENTIANIDAE: plants woody, evergreen; ellagic acid 0, non-hydrolysable tannins not common; vessel elements long, with scalariform perforation plates; sugar transport in phloem active; inflorescence usu. basically cymose; flowers rather small [<8 mm across]; C free or basally connate, valvate, often with median adaxial ridge and inflexed apex ["hooded"]; A = and opposite K/P, free to basally adnate to C; G [#?]; ovules 2/carpel, apical, pendulous; fruit a drupe, [stone ± flattened, surface ornamented]; ="apo">seed single; duplication of the PI gene.
ASTERID I / LAMIIDAE: ?
[METTENIUSALES [GARRYALES [GENTIANALES, VAHLIALES, SOLANALES, BORAGINALES, LAMIALES]]: ?
[GARRYALES [GENTIANALES, VAHLIALES, SOLANALES, BORAGINALES, LAMIALES]]: G , superposed; loss of introns 18-23 in RPB2 d copy
Age. The age of this node is estimated to be (121-)112(-103) Ma (Janssens et al. 2009), (80-)76(-71) Ma (Moore et al. 2010: 95% HPD), 124 Ma (Z. Wu et al. 2014), or ca 104.5 Ma (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 + [trans-1,4-polyisoprene]; 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.
Includes Eucommiaceae, Garryaceae.
Note: In all node characterizations, boldface denotes a possible apomorphy, (....) denotes a feature the exact status of which in the clade is uncertain, [....] includes explanatory material; other text lists features found pretty much throughout the clade. Note that the precise node to which many characters, particularly the more cryptic ones, should be assigned is unclear. This is partly because homoplasy is very common, in addition, basic information for all too many characters 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 are the not-so-trivial issues of how character states are delimited and ancestral states are reconstructed (see above).
Age. Lemaire et al. (2011b) date crown-group Garryales to (91-)63(-31) Ma, Bell et al. (96-)77, 70(-51) Ma, while Wikström et al. (2001) estimated it at (89-)84, 80(-75) Ma and Naumann et al. (2013) at ca 65.9 My; 67.9 Ma is the estimate in Nylinder et al. (2012: suppl.) but about 43.5 Ma in Magallón et al. (2015).
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 of Garryales, see the euasterids.
Synonymy: Aucubales Takhtajan, Eucommiales Cronquist
GARRYACEAE Lindley, nom. cons. - Back to Garryales
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; flowers 4-merous; staminate flowers: A not adnate to C, pistillode +; carpelate flowers: staminodes 0; ovary inferior; large placental obturator +; fruit a berry; testa thick; 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 Ma, Wikström et al. (2001) date them to (57-)52, 42(-37) Ma, Janssens et al. (2009) to 20±8.6 Ma and Bell et al. (2010) to (58-)38, 36(-17) Ma.
1. Garrya Lindley
Diterpenoid alkaloids +; fibres with helical thickening; lamina cartilaginous, margins ± entire; inflorescences axillary, catkinate, bracts ± connate; staminate flowers: P [?= bracteoles] valvate, connate apically; A alternating with P; (pollen colporate[?], partly tectate); nectary 0; pistillode +; carpelate 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?, flavonols, kaempferol +; vascular tracheids present; pericyclic fibres 0; lamina margins serrate; inflorescence terminal; K minute or 0, C with early tube formation, valvate, apex incurved; staminate flowers: pollen surface pilate-capitate; carpelate 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).
Age. Fossils of Aucuba are reported in Eocene deposits ca 50 Ma from the Okanogan Highlands in W. North America (Wehr & Hopkins 1994).
Synonymy: Aucubaceae Berchtold & J. Presl
Evolution: Divergence & Distribution. Fossil leaves of Aucuba are reported from the Eocene of Washington (Wehr & Hopkins 1994).
Pollination Biology. Although Garrya is wind pollinated, it has recently become clear that the little flowers of Aucuba are pollinated by fungus gnats (Mochizuki & Kawakita 2017).
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 carpelate flower. The calyx is reported to be much reduced in staminate flowers, but the corolla is more reduced than the calyx in carpelate 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 nodal anatomy, see Balfour and Philipson (1962: Garrya), for inflorescence morphology, esp. of Garrya, see Jahnke (1986), for some floral morphology of Aucuba, see Reidt and Leins (1994), for pollen, see Ferguson (1977: Aucuba), 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
Trees, deciduous; O-methylated flavonols, little oxalate accumulation, lignans, 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; inflorescences ± fasciculate, axillary; bracteoles 0; P 0; staminate flowers: A 4-12, filaments short, connective prolonged; endothecium biseriate; tapetal cells 2-6-nucleate; pistillode 0; carpelate 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).
Age. The distinctive fossils of Eucommia (distinctive fruits, and the latex canals can be recognized) are well known from Middle and Late Eocene deposits from W. and S.E. U.S.A., Oligocene Europe and younger deposits in Mexico, etc. (Call & Dilcher 1997; Manchester et al. 2009). The oldest fossils are ca 48.6 Ma (Martínez-Millán 2010), but Wuyun et al. (2017) suggest that a Cretaceous age might be appropriate.
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. Sogo and Tobe (2006c) noted that fertilization in Eucommiawas quite a lengthy process. Pollen tubes spent some time growing in the thickened apices of the integument, some of them branching, and ultimately a tube - sometimes more than one - proceeded down the lengthy micropyle. Eckardt (1963) had recorded occasional chalazogamy.
Genes & Genomes. Wuyun et al. (2017) looked at the nuclear genome of Eucommia, i.a. noting the number and high level of expression of genes involved in stress responses, and clarifying the synthesis of gutta.
The plastome of Eucommia had three rearrangements in the large single copy region when compared with that of Aucuba, and the boundary between the inverted repeat and the small single copy region had moved to include the ycf1 gene in the former (L. Wang et al. 2016).
Chemistry, Morphology, etc.. The vessel elements in the primary xylem have scalariform perforation plates (Carlquist 2018b). 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 general information, see L.-B. Zhang (2016), and for embryology, etc., see Z.-Y. 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.