Syn. Pl. 1: 400. 1805
Plants annual or perennial, of fresh waters. Rhizomes and stolons absent [present]. Erect stems rooted in substrate, unbranched, short. Leaves basal, submersed [floating], petiolate; blade lanceolate to reniform [linear], base cuneate to cordate, apex rounded to acute; midvein without rows of lacunae along sides, blade uniform in color throughout; abaxial surface without prickles or aerenchyma, smooth; intravaginal squamules entire. Inflorescences scapose, long-pedunculate; spathes winged or ribbed. Flowers bisexual [unisexual, staminate and pistillate on different plants], sessile [staminate pedicellate], floating or occasionally opening under water; petals white to pink or light violet, often yellow at base; filaments distinct; pollen in monads; ovary 1-locular; styles 3–9, not 2-fid. Fruits oblong, ridged, dehiscing irregularly. Seeds fusiform, covered with hairs.
Introduced; North America, South America, Asia, Africa, Australia.
Species 21 (1 in flora).