South West Africa is one of the arid and semi-arid regions of the world regarded by Christ (1910) as being almost without ferns. This impression can be regarded as accurate if one considers the territory as a whole, ranging from coastal desert, through vast areas of thorn savannah to oceasional, shaded, watered kloofs on mountainsides. However, it became evident to the author on a collecting excursion to the territory in July, 1954, that the majority of species of the fern flora of the region occurred among rocky terrain of scattered rock outcrops or of mountain ranges. The minority of the ferns of South West Africa occur around such terrain in comparatively level ground e.g. Ophioglossum polyphyllum, or in seasonally wet areas, e.g. Marsilea spp. Another feature is the apparent absence of "fern allies" such as Lycopodium, Selaginella, Isoetes and Equisetum from the flora of South West Africa. Nevertheless, the possibility of the occurrence of Isoetes in seasonally wet areas in this territory cannot be excluded in view of the drought resistance of some South African species of the genus and the fact that the author’s visit took place during the dry winter season