sub-aquatic, perennial fern allies. Rhizome creeping, hairy, growing on mud,
submerged or enduring dessication. Fronds erect with circinate in vernation,
spreading or floating, simple and linear or with two or four opposite leaflets
at the end of long stipes. Veins promonent dichotomously branched. Sporangia
enclosed in hard, bean shaped structure, borne on the stipes or their bases and
constructed as fertile pinnae. Sporocarp contains two types of spores
megaspores and microspores. Sorus consists of megasporangia and microsporangia,
megaspore solitary and microspore many.