Stems slender, up to 3 dm. or more long in water, sparingly branched; shorter on mud. Lowest lvs about linear to narrow-lanceolate, ± retuse. Mid-lvs on short petioles; lamina thin, ± 4-10 × 2-4 mm., about spathulate, rounded to emarginate. Uppermost lvs c. 5-15 × 2-5 mm. or more, forming floating rosettes, obovate- to spathulate-oblong, on petioles c. 3 mm. long. ♂ in upper, ♀ in lower axils; bracts falcate, persistent. Fr. suborbicular, c. 1·5-1·6 mm. diam., pale; wing distinctly narrower than cell; commissural groove deep; seeds pale.

Amphibious monoecious herb. Aquatic stems to c. 1 m long, often forming dense mats in water or on mud. Submerged lvs not markedly different from rosette or floating lvs, 4-10-(25) × 2-4-(6) mm, linear-spathulate, spathulate or obovate, but never linear, 3-, 5-, or 7-nerved; free veins 0; apex rounded or slightly emarginate; rosette lvs to 10 × 6 mm, broad-elliptic to suborbicular, entire; terrestrial lvs usually smaller and rarely > 5 × 3 mm. Fls in axils of rosette lvs, solitary or 1 ♂ and 1 ♀ together. Bracteoles white, falcate, persistent. Filaments c. 2 mm long; anthers c. 0.2 mm long. Styles 2-3.5 mm long, persistent and recurving at fruiting. Fr. subsessile, 1.2-1.7 mm diam., orbicular, pale; mericarp faces ± flat; wing rather narrow, usually extending round the mericarp; commissural groove wide, deep, tapering towards the top.