Description from Flora of China
Herbs, annual or perennial, mycotrophic, semi-mycotrophic, or autotrophic, sometimes rhizomatous. Stems simple, rarely branched. Basal leaves in a distinct rosette; cauline leaves bractlike, small. Flowers solitary or in terminal cymes. Perianth tube actinomorphic, cylindric or trigonous, with 3 lateral wings or sometimes wings absent, without annulus at tube mouth; tepals generally 6, apically distinct; outer tepals larger than inner, unlobed; inner tepals often minute, occasionally lacking. Stamens 3, sessile or subsessile on perianth tube; connective with 0-2 apical and 0 or 1 basal appendages. Ovary trigonous, 3-loculed, with axile placentation; stigmas 2-labiate to funnel-shaped. Fruit capsular, with persistent perianth, dehiscence generally irregular.
About 57 species: tropical and subtropical regions; ten species (one endemic) in China.