Family Cornaceae
Cornaceae Dum.Excluding Aucubaceae, Curtisiaceae, Davidiaceae, Griseliniaceae, Helwingiaceae, Mastixiaceae, Melanophyllaceae, Nyssaceae, Toricelliaceae Habit and leaf form. Trees and shrubs, or herbs (rarely); non-laticiferous and without coloured juice. Plants non-succulent; autotrophic. The herbs perennial; rhizomatous. Leptocaul. Mesophytic. Leaves evergreen, or deciduous; opposite (nearly always), or alternate (rarely spiral, e.g. C. alternifolia); ‘herbaceous’, or leathery; usually petiolate; almost connate, or not connate; non-sheathing; gland-dotted, or not gland-dotted; simple; epulvinate. Lamina entire (usually), or dissected (rarely); pinnately veined; cross-venulate. Leaves exstipulate. Vegetative buds scaly, or not scaly. Leaves without a persistent basal meristem. Domatia occurring in the family (from 4 genera); manifested as pockets (mostly), or hair tufts. General anatomy. Plants with ‘crystal sand’, or without ‘crystal sand’. Leaf anatomy. Stomata present; usually anomocytic. Hairs present (commonly unicellular and equally 2–armed). Unicellular hairs branched. Adaxial hypodermis absent. Lamina dorsiventral. Minor leaf veins without phloem transfer cells. Stem anatomy. Cork cambium present; initially superficial. Nodes tri-lacunar. Secondary thickening developing from a conventional cambial ring. Xylem with tracheids; with fibre tracheids; with libriform fibres; with vessels. Vessel end-walls scalariform. Vessels without vestured pits. Wood parenchyma apotracheal. Reproductive type, pollination. Plants hermaphrodite (usually), or dioecious (e.g. C. volkensii). Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in cymes, in heads, in corymbs, and in umbels. The ultimate inflorescence unit cymose. Inflorescences terminal, or axillary; usually in cymes, cymose corymbs, panicles or umbels, in racemes of panicles, or even in heads; with involucral bracts (sometimes), or without involucral bracts; pseudanthial (sometimes), or not pseudanthial. Flowers bracteate; small to medium-sized; regular; 4–5 merous; cyclic; tricyclic, or tetracyclic. Free hypanthium absent. Perianth with distinct calyx and corolla, or sepaline; 4–5, or 8–10; 1 whorled, or 2 whorled; isomerous (usually), or anisomerous. Calyx when resolvable 4–5(–7); 1 whorled; gamosepalous (sepals free as no more than small teeth); entire, or lobulate, or blunt-lobed, or toothed; regular; valvate, or open in bud. Corolla when present, 4–5; 1 whorled; when present, polypetalous; valvate; regular; not fleshy. Androecium 4–5. Androecial members free of the perianth; all equal; free of one another; 1 whorled. Androecium exclusively of fertile stamens. Stamens 4, or 5; isomerous with the perianth; oppositisepalous; alternating with the corolla members. Anthers dehiscing via longitudinal slits; introrse; tetrasporangiate. Microsporogenesis simultaneous. Pollen shed in aggregates (occasionally), or shed as single grains; when aggregated, in tetrads. Pollen grains aperturate; 3 aperturate; colporate; 2-celled. Gynoecium 2(–4) carpelled. Carpels reduced in number relative to the perianth. The pistil 1–4 celled. Gynoecium syncarpous (but occasionally pseudomonomerous); synovarious to eu-syncarpous; inferior. Ovary 1 locular (occasionally, pseudomonomerous), or 2–3(–4) locular. Epigynous disk present. Gynoecium stylate. Styles 1, or 2–4; free, or partially joined; apical. Stigmas dry type; non-papillate; Group II type. Placentation when unilocular parietal; usually axile, or apical. Ovules in the single cavity when unilocular, 1; 1 per locule; pendulous; apotropous; with dorsal raphe, or with lateral raphe (subsequently); non-arillate; anatropous; unitegmic; tenuinucellate to crassinucellate. Endothelium differentiated. Embryo-sac development Polygonum-type, or Fritillaria-type. Polar nuclei fusing prior to fertilization. Antipodal cells formed; 3; not proliferating; ephemeral. Synergids pear-shaped. Hypostase present, or absent. Endosperm formation cellular. Fruit fleshy to non-fleshy; indehiscent; a drupe (usually), or a berry (less often). The drupes with separable pyrenes (with two stones), or with one stone (four-locular). Seeds endospermic. Endosperm oily. Cotyledons 2. Embryo chlorophyllous (3/4). Seedling. Germination phanerocotylar. Physiology, biochemistry. Not cyanogenic. Alkaloids present (commonly), or absent. Iridoids detected (often aucubin); ‘Route I’ type (normal and seco). Verbascosides not detected. Cornoside detected. Proanthocyanidins present, or absent (mostly); when present, cyanidin. Flavonols present; quercetin, or kaempferol and quercetin. Ellagic acid present (Cornus, Macrocarpium). Arbutin absent. Ursolic acid present. Saponins/sapogenins present (rarely), or absent. Aluminium accumulation demonstrated. Inulin recorded. C3. C3 physiology recorded directly in Cornus. Geography, cytology. Temperate (mainly), or sub-tropical to tropical (in mountains). North and South temperate, and tropical mountains, few in Australia. X = 11. Taxonomy. Subclass Dicotyledonae; Tenuinucelli. Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Cornales. APG 3 core angiosperms; core eudicot; Superorder Asteranae; Order Cornales. Species about 60 (?). Genera 1–6 (depending on recognition of segregate genera); Cornus (including Afrocrania, Benthamidia, Chamaepericlymenum, Cynoxylon, Swida, Yinquania etc.). Diplopanax (removed from Cornaceae sensu lato) has yet to be referred to a segregate genus. See Eyde (1988) for a wide-ranging taxonomic discussion. The various sensu lato versions of Cornaceae exemplify the well known difficulties in distributing certain families between Dahlgren’s Araliiflorae and Corniflorae. It is equally hard to assign them with confidence to the higher level groupings Crassinucelli and Tenuinucelli. This is interesting, given that the latter evidently represent a major divergence in the Dicot line of descent (cf.Young and Watson 1970, Chase et al. 1993). Economic uses, etc. Good edible berries from several species, especially Cornus mas. Illustrations. |
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