Plants annual [perennial], of fresh waters. Rhizomes absent [present]; stolons present. Erect stems rooted in substrate, unbranched short. Leaves basal, submersed, sessile; blade of uniform color from margin to margin, with continuous intercellular spaces, linear, base grading into sheath, apex acute; midvein without rows of lacunae along sides, uniform in color throughout from margin to margin, with continuous intercellular spaces; abaxial surfacely without prickles or aerenchyma; intravaginal squamules entire. Inflorescences 1-flowered, flowers rarely paired [cymose], long-pedunculate; spathe not winged. Flowers bisexual [unisexual, staminate and pistillate on different plants], emersed, pedicellate; petals white to reddish; filaments distinct; anthers fusiform; pollen in monads; ovary 1-locular; styles 1, not 2-fid. Fruits cylindric, ridged, dehiscing irregularly. Seeds ellipsoid or fusiform, echinate [without spines and with or without ridges or wings].
Introduced; North America, Asia, Africa, Australia.
Species 9 (1 in flora).