Description from Flora of China
Shrubs or woody lianas, villous or rusty tomentose, rarely glabrous. Cymes axillary, umbel-like. Sepals small, sometimes with minute basal glands. Corolla usually yellow or yellowish, rotate or rarely campanulate; tube very short; lobes patent-reflexed, overlapping to left, rarely to right. Corona lobes 5, inserted at back of gynostegium, dorsally compressed, slightly exceeding stamens. Anthers small, retuse, sometimes with minute apical appendages appressed to stigma head; pollinia 4 on each pollinarium, erect or horizontal. Styles short; stigma head exserted beyond anthers, beaked or swollen. Follicles divaricate, terete, usually villous. Seeds flat, beaked; coma white.
About 40 species: tropical Asia, Africa, and Pacific Islands; ten species in China.
The separation of Toxocarpus from Secamone seems to be somewhat arbitrary, and some authorities favor combining them. Goniostemma and Genianthus are also closely related and also sometimes included (see Forster & Harold, Austrobaileya 3: 69-78. 1989).