Description from Flora of China
Herbs perennial, small, usually with stolons, bulbs, or bulbils. Leaves alternate or opposite, petiolate, exstipulate, simple. Inflorescence a cyme surrounded by bracteal leaves, rarely flower solitary. Hypanthium ± adnate to ovary. Sepals 4(or 5), imbricate in bud. Petals absent. Disc absent, obscure, or distinctly (4 or)8-lobed, sometimes surrounded by brown papillae. Stamens 4 or 8(or 10); filaments subulate; anthers 2-loculed, laterally dehiscent; pollen grains minute, 3-colporoidate, with fine reticulum. Carpels 2, usually connate proximally; ovary subsuperior, semi-inferior, or subinferior, 1-loculed; placentas 2, parietal; ovules many; styles 2, free; stigmas punctate. Fruit a capsule, with 2 subequal or distinctly unequal carpels. Seeds many, ovoid to ellipsoid, smooth, papillose, tuberculate, puberulous, sulcate, or other texture.
About 65 species: Africa, America, Asia, Europe; 35 species (20 endemic) in China.
(Authors: Pan Jintang; Hideaki Ohba)