Identification notes
This is a very distinctive species and is fully aquatic, although it may sometimes be stranded on mud as water levels drop. Though rare, where it is found, many thalli often grow together in dense floating or slightly submerged colonies and these can be very conspicuous. Its appearance, though distinctive, varies depending on whether it is floating in water or stranded on mud. Aquatic forms are usually easily recognised in the field by the dense mat of linear, toothed ventral scales which are often brownish or violet.
Terrestrial plants may look quite different and could be mistaken for one of several species of Riccia with a perforated upper surface, but close examination with a hand lens will reveal some (reduced) toothed ventral scales. Riccia species have inconspicuous ventral scales with entire margins and, apart from R. huebeneriana, lack the obvious median groove of R. natans. In section under the microscope, fresh material of R. natans can be seen to have cell oil bodies, another character lacking in Riccia species.
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