_Hyphomycetes_ are widely diffused; some species are peculiarly cosmopolitan, and all seem to be less influenced by climatic conditions than the more fleshy fungi. The _Sepedoniei_ are represented by at least one species wherever _Boletus_ is found. The _Mucedines_ occur everywhere in temperate and tropical regions, _Penicillium_ and _Aspergillus_ flourishing as much in the latter as in the former. _Botrytis_ and _Peronospora_ are almost as widely diffused and as destructive in warmer as in temperate countries, and although from difficulty in preservation the moulds are seldom represented to any extent in collections, yet indications of their presence constantly occur in connection with other forms, to such an extent as to warrant the conclusion that they are far from uncommon. The _Dematiei_ are probably equally as widely diffused. Species of _Helminthosporium_, _Cladosporium_, and _Macrosporium_ seem to be as common in tropical as temperate climes. The distribution of these fungi is imperfectly known, except in Europe and North America, but their occurrence in Ceylon, Cuba, India, and Australasia indicated a cosmopolitan range. _Cladosporium herbarum_ would seem to occur everywhere. The _Stilbacei_ and _Isariacei_ are not less widely diffused, although as yet apparently limited in species. _Isaria_ occurs on insects in Brazil as in North America, and species of _Stilbum_ and _Isaria_ are by no means rare in Ceylon. The _Physomycetes_ have representatives in the tropics, species of _Mucor_ occurring in Cuba, Brazil, and the southern states of North America, with the same and allied genera in Ceylon. _Antennaria_ and _Pisomyxa_ seem to reach their highest development in hot countries.