Herbs, aquatic or terrestrial. Leaves spirally arranged, many ranked; blade linear to filiform, apex commonly 2-fid. Inflorescences: solitary flowers, morphologically terminal, soon appearing lateral because of sympodial growth of shoots. Flowers: sepals subvalvate; petals imbricate, shortly clawed; nectar and nectaries absent; stamens antisepalous; filaments slender, glabrous; anthers basifixed, sometimes at end of tubular, apical appendage; styles terminal; stigmas terminal. Fruits 3-valved. Seeds ovoid to globose; seed coat reticulate.
3 in warm temperate to tropical America and 1 in w Africa.
Species ca. 4 (1 in the flora).