Description from Flora of China
Shrubs, climbing. Hairs simple or stellate. Stems lenticellate when young. Leaves opposite, short petiolate, margin entire. Inflorescences capitate cymes, 3-7-flowered, subtended by a whorl of 5 or 6 prominent involucral bracts. Calyx funnelform, 5-dentate, sometimes enlarged or inflated in fruit. Corolla tube short cylindric; lobes 5 (or 6), narrowly lanceolate to ovate-oblong. Stamens 5(-7); anthers ovate. Ovary imperfectly 2-locular; ovules 2 per locule, pendulous from apex of a placenta bearing axis. Stigma 2-cleft. Fruit indehiscent, small, obovoid to globose, included or nearly included in calyx, 1- (or 2)-seeded.
About 16 species: mainly in tropical and subtropical Asia, four species in China.