Spikelets mostly 2-fld, disarticulating above the glumes and between the lemmas; rachilla-joint elongate; glumes unequal, obscurely nerved, the second erose at the top; lemmas strongly 3-veined, broadly truncate and ± erose at the scarious summit; palea resembling the lemma, strongly 2-veined; perennial aquatic grasses, prostrate and rooting at the lower nodes, with overlapping sheaths, flat soft blades, and open panicles. 7, mostly in n. Eurasia.