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).