Monographs Details: Azolla caroliniana Willd.
Authority: Mickel, John T. & Beitel, Joseph M. 1988. Pteridophyte Flora of Oaxaca, Mexico. Mem. New York Bot. Gard. 46: 1-580.
Discussion:Type. “Habitat in aquis Carolinae.” Richard s.n. (B-Willd. 20260!).
Similar to A. mexicana except plants 0.5-1.0 cm diam.; leaves small. 0.5 mm long, nearly orbicular, divaricate, nearly smooth, not closely imbricate; glochidia not septate, megaspores unknown.
Azolla filiculoides Lamarck (q.v.) is larger and has papillose leaves. This taxon is often used as a catchall for sterile specimens, but Svensen (1944) maintained that A. caroliniana is confined to the eastern U.S. and perhaps the Greater Antilles.