Herbs, perennial, not cespitose, stoloniferous, aquatic. Culms many-stemmed (branched), with stems in successive false whorls, terete; whorls terminating in clusters of leaves essentially indistinguishale from stems. Leaves sheaths, tubular, transparent, or scalelike when subtending stems; ligules absent; blades absent. Inflorescences terminal; spikelets 1; involucral bracts absent. Spikelets borne singly on branches arising from among leaves; scales 2, distichous, proximal empty, distal subtending flower. Flowers bisexual; perianth bristles 6-11, straight or curved, slightly longer than achene, retrorsely spinulose; stamens 3; styles persistent, linear, 2-fid, base slightly enlarged. Achenes biconvex.