Description from Flora of China
Costantina Bullock; Pilostigma Costantin 1912, not Van Tieghem 1894.
Herbs perennial, twining. Inflorescences extra-axillary and sometimes terminal, lax cymose. Buds truncate. Calyx glands absent(?). Corolla small, campanulate; tube much shorter than lobes; lobes inflexed in bud, overlapping to right, narrowly oblong-falcate, revolute, apex rounded. Corona lobes inserted on backs of anthers, oblong-ovate, dorsiventrally flattened, as high as gynostegium. Anthers short, appendages appressed to stigma head; pollinia 2 per pollinarium, obliquely oblong-falcate, erect to horizontal. Stigma head depressed or exserted and short 2-lobed. Follicles ellipsoid-ovoid, small.
About 3(-6) species: China, Myanmar, Thailand, Vietnam; one species in China.