AZOLLACEAE (Mosquito Fern Family)
One genus, about 7 species. Worldwide, especially in warmer climates.
This unusual family of aquatic ferns is perhaps most closely related to another
heterosporous family of aquatic ferns, the Salviniaceae, with which it is
sometimes combined. Steyermark (1963) included Salvinia natans
(Salviniaceae) in the flora based upon a single historical collection from
Perry County, which has not been relocated. This species differs from Azolla
in having larger (10–15 mm long), unlobed leaves occurring in whorls of 3 at
each node, with 1 of the lobes submerged, dissected, and rootlike. It seems
unlikely that this mainly tropical species could overwinter in Missouri, and
the genus is thus excluded from the flora. However, Salvinia species
commonly are cultivated as aquarium and pond plants, and it seems likely that
they will continue to escape from cultivation sporadically (but not overwinter
to become truly naturalized).