Description from Flora of China
Herbs epiphytic or epilithic. Stems and branches fleshy, usually climbing by adventitious roots, sometimes also twining, or hanging. Leaves opposite or partly in whorls of 3 or 4, fleshy [sometimes leafless]. Inflorescences extra-axillary, small; rachis thick, often branched, eventually elongated, producing a series of often umbel-like groups of flowers. Flowers mostly very small. Calyx with 5 basal glands. Corolla white, red, or violet, ovoid to urceolate, with a narrow mouth, fleshy; lobes valvate in bud, short, often hairy. Corona lobes 5, slender, inserted on gynostegium, erect or ascending, apex entire, notched, 2-cleft, or with recurved arms. Anthers erect, with apical membrane overlying stigma head; pollinia 2 per pollinarium, margin translucent, caudicles enlarged at apex, erect. Follicles lanceolate or cylindric.
About 80 species: tropical and subtropical Asia and Oceania, five in China.