The families of flowering plants

L. Watson and M.J. Dallwitz

Hymenocardiaceae Airy Shaw

~ Euphorbiaceae.

Habit and leaf form. Trees, or shrubs; non-laticiferous, without coloured juice. Leaves deciduous; alternate; spiral; shortly petiolate; densely red gland-dotted (beneath); simple. Lamina entire; pinnately veined, or palmately veined (sometimes three nerved at the base). Leaves stipulate. Lamina margins entire.

General anatomy. Plants without laticifers.

Axial (stem, wood) anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. Primary medullary rays narrow.

The vessel end-walls scalariform and simple. ‘Included’ phloem absent.

Reproductive type, pollination. Fertile flowers functionally male, or functionally female. Plants dioecious. Gynoecium of male flowers pistillodial (the pistillode small).

Inflorescence, floral, fruit and seed morphology. Flowers aggregated in ‘inflorescences’; in racemes, or in spikes, or in catkins. The ultimate inflorescence units racemose. Inflorescences axillary (more or less precocious); rather short, catkinlike spikes or racemes. Flowers regular; 4–6 merous; cyclic. Free hypanthium absent. Hypogynous disk absent.

Perianth sepaline; 4–6; 1 whorled. Calyx 4–6; 1 whorled; polysepalous (the sepals narrow, in the female flowers), or partially gamosepalous to gamosepalous (sometimes irregularly gamosepalous in the male flowers); imbricate.

Androecium 4–6. Androecial members free of the perianth; free of one another, or coherent; 1 whorled. Androecium of male flowers exclusively of fertile stamens. Stamens 4–6; isomerous with the perianth; oppositisepalous; filantherous (the filaments short and spreading). Anthers dehiscing via longitudinal slits; extrorse (and often bearing a dorsal gland). Pollen shed as single grains. Pollen grains resembling those of Celtis.

Gynoecium 2 carpelled. Carpels reduced in number relative to the perianth. The pistil 2 celled. Gynoecium syncarpous; synovarious; superior. Ovary 2 locular (compressed at right angles to the plane of the septum). Gynoecium stylate. Styles 2; long, free. Placentation apical. Ovules 2 per locule; pendulous; anatropous.

Fruit non-fleshy; a schizocarp. Mericarps 2; samaroid (in the form of two winged or winglike cocci, separating from the persistent central axis). Seeds sparsely endospermic; flat.

Geography, cytology. Paleotropical and Cape. Sub-tropical to tropical. Tropical and South Africa, Southeast Asia, Malay Peninsula, Sumatra.

Taxonomy. Subclass Dicotyledonae; Crassinucelli. Dahlgren’s Superorder Malviflorae; Urticales. Cronquist’s Subclass Rosidae; Euphorbiales. APG III core angiosperms; core eudicot; Superorder Rosanae; fabid. APG IV Order Malpighiales (as a synonym of Euphorbiaceae).

Species 5. Genera 1; only genus, Hymenocardia.

General remarks. In terms of this inadequate description, dubiously disinguishable from Euphorbiaceae only by the leaves red gland-dotted beneath, racemose inflorescences, bilocular, 2-styled gynoecium and samaroid mericarps.

Illustrations. • Hymenocardia ulmoides: Hook. Ic. Pl. 12 (1876).

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: 15th April 2018.’.