The genera of the fern families ofOphioglossaceae, Osmundaceae, Stromatopteridaceae, Gleicheniaceae, DipteridaceaeandPlagiogyriaceaeare studied from the point of view of the nomenclature following the plan of work adopted in the two previous accounts of the same series, with the amendments and additions introduced in a recent paper on the names and types of the genera of fern-allies [Webbia26:129–194. 1971].