Hymenocardiaceae Airy Shaw
Habit and leaf form. Trees, or shrubs. Leaves deciduous; alternate; 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.
Stem anatomy. Internal phloem absent. Secondary thickening developing from a conventional cambial ring. ‘Included’ phloem absent. Vessel end-walls scalariform and simple. Primary medullary rays narrow.
Reproductive type, pollination. 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 unit 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 3 core angiosperms; core eudicot; Superorder Rosanae; fabid; Order Malpighiales (as a synonym of Euphorbiaceae).
Species 5. Genera 1; only genus, Hymenocardia.