Small floating moss-like plants, with branching axis, covered with minute 2-lobed imbricated leaves. Sporocarps in pairs beneath the stem, very soft and thin-walled, the smaller ones acorn-shaped, containing a single macrospore, the larger ones globose, containing several microspores.

Azolla,Lam

A. Carolinia'na, Willd. Somewhat deltoid in outline, much branched, of reddish aspect. Floating on quiet waters of Lake Ontario, not common.