Semiaquatic annual herbs, glabrous, erect or suberect, somewhat succulent with spongy tissue. Leaves simple, exstipulate, alternate, lanceolate or elliptic, entire. Inflorescence terminal, a dense cylindric spike. Flowers small, sessile, bracteate, regular, complete; bract 1; bracteoles 2. Calyx 5-lobed; tube short and adnate to the ovary; lobes imbricate, persistent, ovate. Corolla perigynous, 5-lobed, imbricate, campanulate-urceolate, caducous. Stamens 5, alternating with the petals, inserted on the corolla tube; filaments short with rounded 2-celled anthers. Ovary semi-inferior, bilocular; style short with capitate sub-bilobed stigma; ovules numerous on axile placenta, anatropous. Capsule (pyxidium) short, obconic, membranous, 2-locular with circumscissile dehiscence at the level of the calyx-lobes; seeds numerous, minute, oblong, with irregularly plicate-costate testa, almost exalbuminous; embryo straight, subterete.