Description from Flora of China
Centrostemma Decaisne; Otostemma Blume.
Subshrubs or lianas, epiphytic or epilithic, often twining or climbing by adventitious roots. Leaves opposite, fleshy, papery, or membranous. Inflorescences extra-axillary or sometimes terminal, umbel-like, producing a succession of globose or flat-top-ped clusters; old rachis thick, with contiguous pedicel scars. Calyx small, with basal glands. Corolla fleshy, rotate, reflexed, [or campanulate]; lobes valvate, often densely hairy or scurfy inside. Corona lobes 5, depressed patent or adnate vertically to gynostegium, fleshy, glossy when dried, inner angle a tooth incumbent on anthers, outer angle rounded or acute; margin revolute, longitudinally grooved basally. Stamens short connate, apical membrane of anthers appressed against stigma head; pollinia 2 per pollinarium, oblong, erect, with raised, translucent margin. Stigma head discoid, rounded or subapiculate. Follicles often solitary, cylindric-fusiform.
At least 100 species: SE Asia to Oceania; 32 species in China.