Salviniaceae

Floating or semi-aquatic, perennial ferns. Rhizome horizontal, flexuose, sometimes  rooting at nodes; when present, roots free-hanging in the water. Fronds small, branched. Leaves in whorls or 2-lobed, uppermost leaves or lobe photosynthetic and exposed to air, while a lower leaf or lobe is colourless and submerged. Sori consisting of megasporangia or microsporangia enclosed by an indusium (sporocarp wall), borne on submerged leaf or in axil of submerged lower leaf-lobe. Gametophyte minute, growing within spores.