Description from Flora of China
Herbs perennial or rarely annual. Leaves equitant; leaf sheath sometimes with a short ligule; leaf blade linear to ensiform, smooth, papillose, rugose, or scaberulose. Peduncle scapelike, terete to compressed, sometimes winged or ribbed. Spikes few to many flowered; bracts brownish yellow to blackish brown, dull or shining, conchiform, rigid, abaxially minutely papillose toward apex when young, midvein conspicuous, margin scarious, entire, ciliate, fimbriate, or lacerate, apex emarginate, rounded, or acute. Sepals 3; lateral sepals with keel entire, dentate, or ciliate, wings membranous; median (anterior) sepal enclosing corolla or sometimes ± reduced or obsolete, thin and membranous, 1--3(--5)-veined. Petals 3, free; limb obovate; claw long and narrow. Stamens usually 3; filaments flattened; anthers basifixed, extrorse, dehiscing by vertical slits. Staminodes 3 or rarely absent, alternate with petals, often clawed, 2-cleft or 2-brachiate and branches with penicillate hairs. Ovary usually sessile, 1- or 3-loculed or imperfectly 3-loculed. Style filiform, apex 3-branched; stigmas usually U-shaped. Seeds obovoid to ellipsoid, longitudinally striate, apex usually apiculate.
About 280 species: mainly in tropical and subtropical America, some species in Africa, Asia, and Australia; six species (one endemic) in China.