Description: Aquatic or semiaquatic perennials; rhizome creeping, covered with hairs.
Fronds scattered along rhizome, simple, filiform and grass-like.
Sporocarps borne singly at the base of sterile fronds, usually bent downwards and often buried in the substrate; globose, hard and pill-like with numerous megasporangia and microsporangia; dehiscence longitudinal, sporangia and spores shed in a mass of mucilage.
Distribution and occurrence: World: 6 species, Europe, America & Australasia. Australia: 1 species (endemic).
Text by Peter G. Wilson