Description from Flora of China
Herbs or shrubs. Stem pubescent, lanose, or glabrous. Leaves opposite, petiolate. Flowers perfect, arranged in terminal or axillary heads or spikes, flower solitary in axil of a bract, subtended by 2 bracteoles. Tepals 5, erect, membranous, becoming rigid or not after anthesis. Stamens 5; filaments unequal, united to a short cup at base, pseudostaminodes absent or very small; anthers 2-loculed. Ovary ellipsoid or globose; ovule 1, pendulous; style slender; stigma capitate or 2-lobed. Utricles enclosed in perianth, ellipsoid, indehiscent. Seed erect, lenticular, smooth.
About 14 species: Africa, SE Asia; three species (one endemic) in China.