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Plants small, floating aquatics. Stems creeping, branched, bearing hairs but no true roots. Leaves in whorls of 3, with 2 leaves green, sessile or short-petioled, flat, entire, and floating, 1 leaf finely dissected, petiolate, rootlike, and pendent. Submerged leaves bearing sori that are surrounded by basifixed membranous indusia (sporocarps); sporocarps of 2 types, bearing either megasporangia that are few in number (ca. 10), each with single megaspore, or many microsporangia, each with 64 microspores. Spores of 2 kinds and sizes, both globose, trilete. Megagametophytes and microgametophytes protruding through sporangium wall; megagametophytes floating on water surface with archegonia directed downward; microgametophytes remaining fixed to sporangium wall.
Floating, aquatic or semi-aquatic, heterosporous (2 types of spores), 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.
Floating aquatic plants with slender branched siphonostelic rootless rhizomes. Leaves dimorphous, borne in whorls of three, two floating, oblong to orbicular, entire, variously papillate on the aerial surface, the third submerged, finely dissected, hairy and rootlike
Leaves in whorls of three of which two are entire and floating, and the third submerged and finely dissected into root–like segments, which are thickly covered with hairs; floating leaves papillose
Rhizome horizontal, branched, siphonostelic, without roots
Small floating herbaceous plants
