Monoec. herbs with milky acrid sap. Lvs us. alt., stipulate. Fls nude, in compound cymes, subumbellately arranged, grouped within a cyathium; the small teeth alternating with conspicuous glands. ♂ ∞, of solitary stamens; ♀ a pedicelled 3-celled ovary; styles 3, stigmas often bifid; ovules 1 per cell. Fr. a 3-valved capsule. Subcosmopolitan genus of about 2000 spp., as us. understood. The N.Z. sp. also occurs in Norfolk Id.

Usually monoecious, rarely dioecious annual or perennial herbs, shrubs or trees, sometimes succulent, with milky sap. Lvs present or O, stipulate or not, alternate or opposite, usually entire or serrate, rarely lobed. Cyathia solitary, clustered or umbellate; umbels or clusters axillary or terminal, simple or compound and often forming many times compound dichasia; rays and cyathia usually subtended by lvs. Fls lacking a perianth, grouped in cyathia consisting of a cup-shaped involucre with usually 4-5 petal-like glands; glands serrate, entire, or with 2 horns; cyathium usually with several ♂ fls each consisting of a single stamen jointed to a pedicel and often separated from each other by small bracteoles, and a single usually longer-pedicellate (rarely sessile) ♀ fl.; ovary usually 3-celled with a single ovule in each cell; styles usually 3, often 2-fid at tips. Fr. usually a 3-celled capsule separating at maturity from the persistent axis; seeds smooth or variously sculptured.