Aquatic or paludal, annual or perennial herbs. Leaves alternate, entire or trifoliolate, sometimes peltate, exstipulate. Petiole sheathing. Inflorescence racemose, solitary or fasciculate or involucrate heads. Flowers bisexual, regular. Calyx 5-parted; corolla 5-Iobed, united, lobes valvate or induplicate valvate, fringed or barbed. Stamens 5, alternating with corolla lobes, epipetalous, anthers dithecous, sagitatte and versatile, glands 5, alternating with stamens. Ovary unilocular, borne on somewhat fleshy disc, placentation parietal. Style 1, bifid at the apex. Fruit a unilocular, few to many seeded capsule, 2 or 4 valved. Seeds winged or not with a crustaceous seed coat.