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The families of flowering plants

L. Watson and M.J. Dallwitz

Davidiaceae Takht.

~ Cornaceae, Nyssaceae.

Habit and leaf form. Trees. Leaves deciduous; alternate; simple. Lamina entire; broadly ovate; pinnately veined; cross-venulate; cordate. Leaves exstipulate. Lamina margins dentate.

General anatomy. Plants without ‘crystal sand’.

Leaf anatomy. The leaf lamina dorsiventral. Hairs present; exclusively glandular (and no 2-armed hairs present). The mesophyll containing crystals. The crystals exclusively solitary-prismatic (only in the spongy mesophyll). Main veins embedded. Minor leaf veins without phloem transfer cells.

Axial (stem, wood) anatomy. Cork cambium present; initially superficial. Internal phloem absent. Secondary thickening developing from a conventional cambial ring.

The vessel end-walls scalariform. The parenchyma apotracheal. ‘Included’ phloem absent.

Reproductive type, pollination. Plants andromonoecious. Female flowers with staminodes (‘the female-fertile flowers with few to many small staminodes inserted halway up the ovary’ (Airy Shaw 1973)). Gynoecium of male flowers absent.

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in heads. Inflorescences terminal; dense, terminal, pedunculate, globular capitula, each with many scarcely distinct male flowers and a single, obliquely terminal hermaphrodite (or female?) one; with involucral bracts (each capitulum subtended by a pair of large, unequal, drooping, white, petaloid bracts); pseudanthial.

Perianth vestigial (perhaps, in the hermaphrodite flowers), or absent (the male flowers consisting of stamens only, the female more or less limited to an ovary and stamens (plus staminodes?)).

Androecium in male flowers, 5–6. Androecial members free of one another. Androecium exclusively of fertile stamens (in male flowers), or including staminodes (in the terminal, hermaphrodite flower, according to Airy Shaw). Stamens 5–6; filantherous (the filaments long). Anthers dehiscing via longitudinal slits; tetrasporangiate; unappendaged. Pollen grains aperturate; 3 aperturate; colporate.

Gynoecium 6–10 carpelled. The pistil 6–9 celled. Gynoecium syncarpous; synovarious to synstylovarious; inferior. Ovary 6–9 locular. Epigynous disk absent. Gynoecium stylate. Styles 1 (columnar, exceeding the androecium). Stigmas 6–10 (‘the style with 6–10 branches’); dry type; non-papillate; Group II type. Placentation axile. Ovules 1 per locule; pendulous; epitropous; with ventral raphe; anatropous; unitegmic; more or less crassinucellate. Endothelium differentiated. Endosperm formation cellular.

Fruit fleshy; indehiscent; a drupe (pear-shaped, about 3.5 cm long, with granular mesocarp). The drupes with one stone (endocarp bony, longitudinally sulcate, 3–5 locular). Seeds endospermic. Endosperm oily. Embryo well differentiated (rather large). Cotyledons 2. Embryo straight.

Seedling. Germination phanerocotylar.

Physiology, phytochemistry. Not cyanogenic. Verbascosides not detected. Arbutin absent. Iridoids detected; ‘Route I’ type (+seco). Saponins/sapogenins present and absent. Proanthocyanidins absent. Flavonols present; kaempferol and quercetin. Ellagic acid present.

Geography, cytology. Holarctic. Temperate. China. N = 21.

Taxonomy. Subclass Dicotyledonae; Tenuinucelli (?). Dahlgren’s Superorder Corniflorae; Cornales. Cronquist’s Subclass Rosidae; Cornales. APG III core angiosperms; core eudicot; Superorder Asteranae. APG IV Order Cornales (as a synonym of Cornaceae).

Species 1 (Davidia involucrata). Genera 1; only genus, Davidia.

General remarks. See Eyde (1988). Differing from Cornaceae sensu stricto (q.v.) in numerous characters involving perianth, gynoecium, ovules and seed, Davidia exemplifies the well known difficulties in distributing certain Dicot families between Dahlgren’s Araliiflorae and Corniflorae. It is equally hard to assign them with confidence to the higher level groupings Crassinucelli and Tenuinucelli, although the latter evidently represent a major divergence in the Dicot line of descent (cf.Young and Watson 1970, Chase et al. 1993).

Illustrations. • Davidia involucrata: Hook. Ic. Pl. Pl. 20 (1891). • Davidia involucrata (Chittenden). • Davidia involucrata (Hutchinson).

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: 5th March 2018.’.