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Free-floating, aquatic, heterosporous ferns. Rhizome slender, creeping, branched, ± protostelic or solenostelic, bearing trichomes; true roots absent; vernation not circinnate. Leaves in whorls of 3, dimorphic; foliar leaves 2, floating, with a distinct midrib and anastomosing veins; third leaf descending, dissected, root-like. Sporocarps developing on submerged leaf, enclosed by a thin indusium, either microsporangiate and producing numerous microspores or megasporangiate and producing 1 megaspore; sometimes both types produced together (not in Australia). Spores trilete, lacking chlorophyll; microspores minutely rugulose; megaspores finely perforate. Gametophytes developing in floating spores, partly projecting through the spore wall.
Floating aquatic ferns with short stems lacking roots. Lvs in whorls of 3, dimorphic: 2 green, floating, entire, elliptic, c. 0.5-2.5 cm long, papillate on upper surfaces, with anastomosing veins; 1 submerged, highly branched and appearing root-like. Mega-and microsporangia borne separately in stalked sporocarps on the submerged lf. Spores trilete.
Stems with many multicellular hairs. Leaves horizontally spreading. Blades of floating leaves green and pubescent abaxially (on side away from water). Sporocarps borne on chainlike or cymelike organs or submerged leaves; sporangia indehiscent, dispersed as units when sporocarps decay.
Leaves at least 1 cm long, simple, floating with upper surface fully exposed.
