Description from Flora of China
Subshrubs or vines, perennial. Roots tufted, tuberous, fusiform, fleshy. Stems erect or climbing. Leaves whorled, opposite, or alternate, shining. Inflorescences axillary, sometimes borne on petiole or leaf midvein. Perianth segments subequal, lanceolate, many veined. Stamens erect, inserted at base of perianth segments; filaments free or basally ± connate; anthers basifixed, apex often adaxially appendaged; connective extended into a perianthlike, linear-lanceolate, long appendage. Ovary superior; ovules basally attached to placenta. Capsule ovoid to oblong. Seeds erect, oblong, longitudinally ribbed; funicle bearded.
About 27 species: Asia, Australia; seven species (five endemic) in China.