Mickel, John T. & Beitel, Joseph M. 1988. Pteridophyte Flora of Oaxaca, Mexico. Mem. New York Bot. Gard. 46: 1-580.
Genus Description - Terrestrial; rhizome horizontal, stout, with persistent, tough leaf bases, wiry roots dense; stipe bases somewhat flared; fronds crown-forming, dimorphic or hemidimorphic; sterile blade pinnate-pinnatifid to bipinnate, lamina glabrous but axes densely hairy, at least when young; fertile areas (fronds or pinnae) lacking lamina entirely; sporangia abundant, dense on fertile axes, globose, opening vertically by a lateral annular patch of cells; spores tetrahedral-globose, green.
Lectotype (chosen by Léman?, Diet. sci. nat. 37: 9. 1825): Osmunda regalis Linnaeus. Osmundastrum Presl, Gefássbündel Farm 18. 1847. Type: Osmundastrum cinnamomeum (Linnaeus) Presl [=Osmunda cinnamomea Linnaeus]. For details of typification of these names, see Pichi Sermolli (Webbia 26: 506. 1972). Osmunda has 14 species of temperate and subtropical regions, occurring mostly in marshes and swamps. The two Mexican species are very widespread, but uncommon in Oaxaca. They are sometimes, but not commonly, segregated into two genera. The other two genera in the family, Todea and Leptopteris, both of the Old World, have sporangia borne on relatively unmodified pinnae. Osmunda is distinct by its dimorphic fronds more than once-pinnately divided, free veins and rhizome indument of hairs. References: B enedict, R. C. 1909. Osmundaceae. N. Amer. Flora 16:27, 28; Bobrov, A. 1968. Species novae Osmundacearum. Novit. Syst. Pl. Vasc. 1968: 8.