POACEAE  

Aquatic annuals; culms branched from base and geniculate or prostrate-ascendent with culms and false petioles containing air canals. Leaves: lamina floating; lower leaves on long false petioles; upper surface raised into sinuous longitudinal lamellae; ligule membranous. Inflorescence a slender spiciform panicle, sometimes reduced to a unilateral raceme with paired spikelets. Spikelets dorsally compressed; lower glume half as long as spikelet, hyaline, truncate; upper glume equalling spikelet and gibbous; upper lemma cartilaginous with flat margins. Lodicules 2, minute. Stamens 3; anthers oblong. Ovary glabrous; style free, terminal.

Caespitose perennials; culms 1

Trailing, mat-forming annuals in swamps or shallow water; culms up to 0.3 m high, base decumbent and rooting at nodes. Leaves up to

Tough, stoloniferous perennials; stolons rooting to form dense tussocks; culms rigid, woody, branching to form fascicles at nodes. Leaf blades narrowly linear to setaceous, flat or involute, stiff, glaucous. Inflorescence of short racemes scattered along and appressed to an elongated central axis. Spikelets several-flowered, shortly pedicelled, laterally compressed, disarticulating above glumes and between florets; callus conspicuously barbate with hairs

Herbaceous perennials with creeping rhizomes and with culms either bearing leaves and inflorescences on same culm, or culms either sterile and bearing leaves mainly in upper part, or fertile and leafless except for leaf sheaths near base. Leaves: sheaths strongly striate; blades ovate-lanceolate to oblong-elliptic, narrowing abruptly near base into a pseudopetiole. Inflorescence terminal, racemose or paniculate. Spikelets linear, bearing up to 25 florets, the lower 1