Aquatic or semi-aquatic perennials. Culms decumbent to stoloniferous, many-noded, rooting at lower nodes or floating. Leaf sheaths compressed; leaf blades linear to lanceolate; ligule membranous or ciliate. Inflorescence open or contracted, composed of racemes on all sides of a common axis; racemes solitary or grouped, rachis slender, bearing 1 to several alternate shortly pedicelled spikelets, terminating in a bristle. Spikelets lanceolate, terete or slightly dorsally compressed, florets 2; lower glume very small, veinless; upper glume equaling the spikelet, firmly herbaceous, scabrous to setose, long-acuminate or briefly awned; lower lemma resembling upper glume but usually slightly shorter, enclosing a shorter hyaline palea; upper floret 1/2 as long, shortly stipitate, membranous, smooth, shiny. Caryopsis eventually much larger than upper floret and filling spikelet when mature. x = 7, 9.
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