Flora of Thailand
Kongkanda Chayamarit & Peter C. van Welzen
Herbs, shrubs or trees, seldom climbers; monoecious or dioecious; stems sometimes spiny or succulent and cactus-like; with or without coloured or white latex. Indumentum absent or of simple, urticating (stinging), stellate and/or lepidote hairs especially on the lower leaf surface and in the inflorescences. Stipules usually present, free, rarely connate, persistent or usually caducous, sometimes glandular. Leaves alternate or opposite (or pseudo-whorled), simple or seldom trifoliolate, sometimes reduced to scales, usually petiolate, base often with two glands, margin entire to variously crenate, dentate or serrate, teeth often glandular, sometimes palmately lobed; venation pinnate or basally palmate. Inflorescences cauliflorous, to usually axillary or terminal, cymose-derived, but very variable in form: spikes, racemes, cymes, thyrses, panicles, solitary flowers, faciculate flowers or pseudo-flowers (cyathia in Euphorbia and Pedilanthus), unisexual or bisexual, the bisexual usually with the pistillate flowers proximal and the more numerous staminate flowers distal; bracts present, often basally glandular, with a single (usually pistillate) or several (usually staminate) flowers; bracteoles absent or indistinct to 2 inside the bract to several. Flowers unisexual (seldom bisexual), usually actinomorphic, pedicellate or sessile; sepals usually 3 or 5, seldom absent, free or partly connate, valvate or imbricate; petals usually absent (especially in pistillate flowers) or usually 5, smaller or longer than sepals; disc usually present, annular or of separate lobes, usually outside the stamens or ovary. Staminate flowers: stamens 1 to usually many, filaments free to variously united; anthers with 2-4 thecae, opening with longitudinal slits; pistillode present or absent. Pistillate flowers: staminodes seldom present; ovary superior, 1- to many-locular, usually 3-locular; ovules 1 or 2 in each locule, apically attached to the central column; style absent or present; stigmas usually as many as locules, lobed (or disciform), apically often partly to completely split, often with long (branched) papillae on upper surface. Fruits usually capsules (schizocarps or rhegmas), sometimes indehiscent drupes or berries (transitions exist: tardily splitting fleshy capsules), dehiscense usually septicidally and loculicidally, sometimes one fruit only partly so, leaving bivalved segments, columella persistent. Seeds usually 3 or 6, often not all developing, smooth (to warty), naked or with an apical fleshy caruncle or partly to completely covered by an aril; endosperm usually copious and oily.
The family occurs worldwide except in the polar and subpolar regions, the great majority of species in tropical and subtropical regions, with ca. 300 genera and ca. 5,000 species.
Eighty-seven genera and ca. 425 species in Thailand.