Description: Aquatic or subaquatic annuals; rhizome short, erect, spongy, bearing a few thin, translucent scales on the apex.
Fronds in a rosette, dimorphic; stipe green, spongy, often bearing roots on its base. Sterile fronds floating or emergent, pinnately compound with broad lobes, veins anastomosing. Fertile fronds erect, more deeply dissected into linear ultimate segments, with edges reflexed to meet and completely cover the lower surface.
Sporangia solitary on the veins, in 2 marginal rows, covered by the false indusium.
Distribution and occurrence: World: 3 species, pantropical. Australia: 2 species, Qld, N.S.W., N.T., W.A., chiefly tropical
Text by Peter G. Wilson