Plants floating, small. Stems horizontal, slender, covered with dark brown articulate hairs. Fronds in whorls of 3, sessile or very shortly stipitate; two fronds floating on water surface, green, entire, herbaceous, densely covered with papillae on upper surface, costae slightly distinct; veins obliquely spreading; third frond submersed and finely dissected, densely hairy, and rootlike. Sporocarps clustered at stipe bases of submersed fronds, or in 2 rows along midrib of submersed frond; microsporocarp large, thin-walled, and containing many microsporangia on a branched receptacle, each microsporangium containing 64 microspores; megasporangia vase-shaped, each one only containing 1 megaspore, trilete, perispore absent; microspores ?covered, trilete, mark usually retuse, triangular, perispore absent, exospore thinner, smooth. x = 9.

About ten species: worldwide, mostly in American and African tropics; two species in China.