Annuals or perennials, often aquatic, with culms often geniculate at base. Ligule reduced to a ciliate rim. Leaf-blade usually closely and prominently ribbed adaxially. Inflorescence a loose or open panicle, or contracted, with small or minute pedicelled spikelets borne singly along the branches. Spikelets dorsiventrally compressed, 2-flowered, florets awnless separated by well-developed rachilla; disarticulation above glumes and usually between florets; lower floret ☿ or ♂, upper floret ♀ or ☿. Glumes ± equal, from c. ⅔ to ≈ spikelet, membranous, glabrous or hairy; lower 3-9-nerved, upper 5-9-nerved. Lower floret: lemma = spikelet or < glumes, membranous, chartaceous or finely coriaceous, glabrous or minutely hairy, obscurely 5-7-nerved; palea = lemma, 2-nerved. Upper floret: lemma of similar size and texture to lemma of lower floret, or somewhat smaller and firmer, often hairy; palea similar to lemma with 2 well-separated nerves; lodicules 2, minute, cuneate, fleshy, glabrous; stamens 3; ovary apex glabrous, styles free, terminal; caryopsis dorsiventrally compressed, embryo large, ⅓ length of caryopsis, hilum basal, > ½ length of caryopsis. Fig. 23.