Description from Flora of China
Herbs perennial, aquatic or along water margins, glabrous throughout. Roots fascicled, fusiform or fibrous. Stem solitary, striate, branched, rooting at lower nodes. Basal leaves petiolate, sheathing; leaf blade 1-pinnate; pinnae sessile, remote. Umbels compound, terminal and lateral; bracts and bracteoles present, usually recurved; rays spreading-ascending. Calyx teeth conspicuous or minute, often unequal. Petals white, obovate or subround, base cuneate, apex notched with small incurved lobule, outer petals in umbellule sometimes enlarged (radiant). Stylopodium short-conic; styles divergent or reflexed. Fruit ovoid or ellipsoid, slightly compressed laterally, glabrous; ribs prominent, corky-thickened or obscure; vittae 1–3 in each furrow, 2–6 on commissure. Seed face plane. Carpophore 2-cleft to base.
About ten species: Africa, Asia, Europe, North America; five species (one endemic) in China.
(Authors: Pu Fading (溥发鼎 Pu Fa-ting); Mark F. Watson)