Description from Flora of China
Annuals or perennials. Leaf blades linear to convolute; ligule membranous. Inflorescence a narrowly cylindrical, densely spikelike panicle. Spikelets asymmetrical, lanceolate-oblong to ovate, usually laterally or rarely dorsally compressed, plump, florets 2; glumes prominently ribbed, lower glume 1/4–3/4 spikelet length, broad, loose and slightly inflated, upper glume equaling spikelet, deeply concave and gibbous on the back; lower lemma resembling upper glume but less gibbous, staminate or neuter, its palea often much reduced; upper floret readily deciduous, the lemma dorsally compressed, often much shorter than spikelet, thinly coriaceous to cartilaginous, smooth, shiny, margins inrolled or flat but never hyaline. x = 9.
This is a genus of aquatic and marshland grasses, recognized by the spikelike panicle of asymmetrical, ribbed spikelets.
About 30 species: tropics, predominantly in Africa; three species in China.
(Authors: Chen Shouliang (陈守良); Sylvia M. Phillips)