Perennials, Aquatic, growing in or on water, Aquatic, leaves floating on surface, Aquatic, fresh water, Terrestrial, not aquatic, Stolons or runners present, Stems trailing, spreading or prostrate, Stems nodes swollen or brittle, Stems geniculate, decumbent, or lax, sometimes rooting at nodes, Stems terete, round in cross section, or polygonal, Stem nodes bearded or hairy, Stem internodes solid or spongy, Stems with inflorescence 1-2 m tall, Stems, culms, or scapes exceeding basal leaves, Leaves mostly cauline, Leaves conspicuously 2-ranked, distichous, Leaves sheathing at base, Leaf sheath mostly open, or loose, Leaf sheath smooth, glabrous, Leaf sheath and blade differentiated, Leaf blades linear, Leaf blades 1-2 cm wide, Leaf blades 2 or more cm wide, Leaf blades mostly flat, Leaf blades mostly glabrous, Leaf blades scabrous, roughened, or wrinkled, Ligule present, Ligule an unfringed eciliate membrane, Ligule elongated, 1-3 cm, Inflorescence terminal, Inflorescence an open panicle, openly paniculate, branches spreading, Inflorescence solitary, with 1 spike, fascicle, glomerule, head, or cluster per stem or culm, Inflorescence curved, twisted or nodding, Inflorescence branches more than 10 to numerous, Lower panicle branches whorled, Flowers unisexual, Plants monoecious, Spikelets pedicellate, Spike lets laterally compressed, Spikelet less than 3 mm wide, Spikelets with 1 fertile floret, Spikelets solitary at rachis nodes, Spikelets unisexual, Spikelets falling with parts of disarticulating rachis or pedicel, Rachilla or pedicel glabrous, Monoecious - staminate and pistillate spikelets on same inflorescence, Glumes completely absent or reduced to cuplike structure, Lemmas thin, chartaceous, hyaline, cartilaginous, or membranous, Lemma 3 nerved, Lemma glabrous, Lemma apex acute or acuminate, Lemma distinctly awned, more than 2-3 mm, Lemma with 1 awn, Lemma awn 1-2 cm long, Lemma awned from tip, Lemma straight, Palea present, well developed, Palea about equal to lemma, Stamens 6, Styles 2-fid, deeply 2-branched, Stigmas 2, Fruit - caryopsis, Caryopsis ellipsoid, longitudinally grooved, hilum long-linear.