FZ volume:0 part:0 (1970) Azollaceae by E. A. C. L. E. Schelpe
Floating aquatic plants with slender pinnately branched siphonostelic rhizomes and with roots borne singly or in fascicles. Leaves alternate, imbricate, 2-lobed, with an aerial chlorophyllous lobe and a thin colourless submerged lobe. Sori in thin-walled Sporocarps borne on the basal leaf of a branch, heterosporous; microsporocarp with numerous microsporangia; megasporocarp with single megaspore surmounted by apical massulae. Female gametophyte submerged; microspores germinating in a massula derived from the microsporangial contents.