Annuals or perennials, rooting in mud or free-floating. Vegetative stem submersed and growing to surface, or emersed and short; flowering stem emersed and glabrous to glandular-pubescent. Sessile leaves forming a basal rosette or alternate on an elongate stem, acuminate at apex; petiolate leaves floating or emersed, cordate to oblong, acuminate to obtuse at apex. Inflorescence a panicle or spike, the inflorescence developing in one to several days, individual flowers open one day only; peduncle glabrous to glandular-pubescent, the subtending spathe folded with an acuminate to caudate apex or sometimes a leaf-like extension. Flowers funnelform, the tepals oblanceolate, glandular-pubescent, obtuse to acute at apex; stamens 6, the 3 upper stamens shorter than the 3 lower ones, filaments purple, glandular-pubescent, curved upwards towards the apex, anthers yellow, rounded to oblong; ovary ovoid, incompletely 3-locular, each locule with many ovules; heterostylous or homostylous. Fruit a capsule; seeds many, ovoid, the testa with longitudinal wings and cross-striae between wings.