Description from Flora of China
Herbs, annual or occasionally perennial, tenuous, with thin fibers. Leaves cauline, sheathing, without a ligule, regularly spaced along stem; leaf blade linear, short. Inflorescence a capitate cyme, condensed, exserted from leaf sheath. Spikelets unisexual. Male spikelets basal on inflorescence; glumes usually 3, usually thin and narrow, each with 1 or 2 male flowers. Female spikelets apical on inflorescence; glumes 2, opposite, equal in size, veined, each with 1 female flower, apex 3-lobed or not. Male flowers: anthers 1-3. Female flowers: stigmas 3. Disk present. Nutlet small, globose, with vertical ribs or reticulate, sometimes apically hairy, tightly enclosed in 2 subtending glumes and shed with them.
About six species: tropics into warm temperate regions of both hemispheres; two species in China.
(Authors: Zhang Shuren (张树仁); Gordon C. Tucker, Jeremy J. Bruhl)