Aquatic or marsh herbs. Leaves simple, basal or alternate except sometimes on the flowering stems; stipules absent. Flowers regular, bisexual, in cymes. Calyx tubular; lobes 5, imbricate. Corolla tubular; lobes 5, valvate, winged. Stamens 5, alternating with the corolla lobes, epipetalous. Ovary superior or half-inferior, 1-locular, with parietal placentas; style simple. Fruit a capsule; seeds numerous. 5 gen., temp. to trop.