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The families of flowering plants

L. Watson and M. J. Dallwitz

Cornaceae Dum.

Excluding Aucubaceae, Curtisiaceae, Davidiaceae, Griseliniaceae, Helwingiaceae, Mastixiaceae, Melanophyllaceae, Nyssaceae, Toricelliaceae.

Habit and leaf form. Trees and shrubs, or herbs (rarely). 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. Leaf development not ‘graminaceous’. Domatia occurring in the family (known from 4 of the segregate genera); manifested as pockets (mostly), or hair tufts.

General anatomy. Plants with ‘crystal sand’, or without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral. Stomata present; usually anomocytic. Hairs present (commonly unicellular and equally 2–armed, usually lime-encrusted). Unicellular hairs branched. Adaxial hypodermis absent. Minor leaf veins without phloem transfer cells.

Axial (stem, wood) anatomy. Secretory cavities absent. Cork cambium present; initially superficial. Nodes tri-lacunar. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls scalariform. The vessels without vestured pits. The axial xylem with tracheids; with fibre tracheids; with libriform fibres. The 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 units 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.

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, phytochemistry. C3. C3 physiology recorded directly in Cornus. Inulin recorded. Not cyanogenic. Alkaloids present (commonly), or absent. Verbascosides not detected. Cornoside detected. Arbutin absent. Iridoids detected (often aucubin); ‘Route I’ type (normal and seco). Saponins/sapogenins present (rarely), or absent. Proanthocyanidins present, or absent (mostly); when present, cyanidin. Flavonols present; quercetin, or kaempferol and quercetin. Ellagic acid present (Cornus, Macrocarpium). Ursolic acid present. Aluminium accumulation demonstrated.

Geography, cytology. Temperate (mainly), 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.

General remarks. 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; and 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). Assuming that this attempt at a sensu stricto version of Cornaceae is error free and does not under-estimate significant variation, comparisons of the descriptions compiled here provide reasonable grounds for retaining the numerous small segregates (see above) as separate families.

Economic uses, etc. Good edible berries from several species, especially Cornus mas.

Illustrations. • Technical details: Cornus sanguinea. • Technical details: Dendrobenthamia (Lindley). • Cornus sanguinea (B. Ent., 1834). • Two-armed foliar trichomes of Cornus nuttallii, with leaf anatomical details of Alangiaceae, Argophyllaceae and Nyssaceae: Solereder, 1908.

We advise against extracting comparative information from the descriptions. This is much more easily achieved using the DELTA data files or the interactive key, which allows access to the character list, illustrations, full and partial descriptions, diagnostic descriptions, differences and similarities between taxa, lists of taxa exhibiting or lacking specified attributes, distributions of character states within any set of taxa, geographical distribution, genera included in each family, and classifications (Dahlgren; Dahlgren, Clifford, and Yeo; Cronquist; APG). See also Guidelines for using data taken from Web publications.

Cite this publication as: ‘Watson, L., and Dallwitz, M.J. 1992 onwards. The families of flowering plants: descriptions, illustrations, identification, and information retrieval. Version: 19th October 2016.’.