Fascicle 4 deals with two fern familes: Dennstaedtiaceae and Hymenophyllopsidaceae. The former consists of about 45 species, mainly tropical, occurring in America, in Madagascar and the Mascarenes, the warmer parts of Asia and in the Pacific, 12 of them in America, from Canada to South America: the Guianas, Colombia, south to Bolivia, Chile and Argentina. The latter consists of eight species, from Guyana and the tepuis of southern Venezuela, but also eastward where the Roraima sandstone occurs. It is epipetric on clif faces and ledges or terrestrial at the base of boulders.