Glabrous, often tall, aquatic perennials, with creeping and rooting bases or with creeping rhizomes. Leaf-sheath often closed. Ligule membranous. Leaf-blade flat. Culm robust or slender, erect, or often decumbent and ascending. Inflorescence a ± lax panicle; rachis trigonous. Spikelets ovate to linear, florets 3-many, often closely imbricate; disarticulation above glumes and between florets. Glumes unequal or subequal, persistent, usually hyaline, 1-(3)-nerved, < lowest lemma. Lemma 5-11-nerved, broad, rounded, usually obtuse, awnless, nerves parallel, usually prominent. Palea ≈ lemma. Lodicules 2, small, ± connate, fleshy, glabrous. Stamens 3. Ovary apex glabrous; styles free. Caryopsis dorsiventrally compressed, longitudinally grooved; embryo small; hilum ± linear. Fig. 8.