Description from Flora of China
Annual or perennial. Culms robust, erect or decumbent, sometimes floating, usually solid. Leaves cauline; leaf blades large, usually broad, flat; ligule membranous. Inflorescences many, fascicled in the upper leaf axils, each subtended by a globose or elongated, bony or sometimes softer modified involucral spatheole ("utricle"); each inflorescence comprising 2 racemes, a female sessile raceme enclosed within the utricle, and a pedunculate male raceme subtended by a prophyll and exserted from the apical pore of the utricle. Female raceme of 1 sessile fertile spikelet accompanied by 2 free stout pedicels, sometimes bearing vestigial spikelets. Female spikelet: lower glume broad, infolding spikelet, membranous with cartilaginous beak; upper glume narrower, keeled; lower floret reduced to a broad hyaline lemma; upper floret with hyaline lemma and palea; lodicules absent; stigmas 2, elongate, exserted from utricle. Male raceme deciduous at maturity, composed of imbricate spikelets borne in pairs or triads, 1(–2) sessile and 1 pedicelled, pedicelled spikelet often reduced in triads. Male spikelets: glumes subequal, herbaceous; lower glume flat on back, margins keeled, keels winged upward, wings with obvious branching veins; upper glume boat-shaped; both florets staminate, lemma and palea hyaline. Caryopsis orbicular, ventrally furrowed, enclosed in utricle.
Four species: tropical Asia; two species in China.
(Authors: Chen Shouliang (陈守良); Sylvia M. Phillips)