Plants submersed, with floating leaves. Stems short, erect; stolons often present, terete. Leaves basal, floating or submersed, submersed sessile phyllodia, floating long-petiolate; petioles terete, septate, with a sheathing base; blades orbicular to oblong-lanceolate, margin entire, apex mucronate to obtuse, base rounded to cordate. Inflorescences of few to numerous flowers, terminating a long septate scape, proliferating with leaves and stolons, scapes few to many; peduncles terete, septate; bracts elliptic to lanceolate, delicate, separate, shorter than pedicel subtended. Flowers long-pedicellate, pedicels cylindric, terete; sepals green, coriaceous, erect, elliptic, apex cucullate, sometimes with a midvein; petals yellow to white, delicate, oblong-obovate to orbicular, falling off soon, erect to spreading, longer than or shorter than sepals; stamens 6-many, in 1-several series, outer often sterile, filaments linear or narrowly elliptic, flattened, anthers linear; carpels 5-8, terete, linear-elliptic, basally scarcely cohering, attenuate into style, styles curved inward, papillose at apex. Fruits more or less terete, linear-elliptic, membranous, without dorsal furrows, dehiscing along inner margins; seeds numerous, sparsely glandular pubescent.
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Emergent aquatic, perennial or annual, stoloniferous, the juveniles usually submerged. Stems mostly floating, attached to substratum, rooting at nodes. Leaves radicalor in clusters along stem; petiole much longer than blade, with transverse septa; blade mostly floating, ovate to suborbicular, obtuse. Inflorescence of axillary clusters, umbels, or flowers solitary. Petals usually yellow. Stamens 6–numerous; staminodes usually present. Ovary superior; carpels usually 3 or 6 (–8), free or fused at base. Fruiting carpels linear-lanceolate, c. 15 mm long, united at base; style beak-like, persistent. Seeds small, curved.
Glabrous, lactiferous aquatic herbs. Stems rooting at nodes. Leaves floating. Flowers solitary, occasionally crowded; sepals 3, persistent; petals 3, delicate yellow, deciduous. Stamens many, outer staminodia. Carpels 3-6-(8), ± connate at base; style short. Follicles free, membranous. Spp. 4, of tropical S. America. Adventive sp. 1.