Thirteen phylogenetic principles of general or mycologicai application are presented. Adherence to these principles makes it difficult to accept any starting point for the Basidiomycetes other than a primitive ascomycete very close toTaphrinaand parasitic upon ancient ferns. From the ancestral basidiomycete one line led to the rusts and another, via the parasitic Auriculariaceae, to the remaining Heterobasidiomycetidae and the Homobasidiomycetidae. In this second line the trend has been toward increasing saprophytic ability, increasing frequency of clamp connections, and increasing complexity of fruit body. The evolution of the rusts is traced from the taphrina-like ancestor to the higher Melampsoraceae. A generalized phylogeny of the Phycomycetes and Ascomycetes and a chronology of the strictly parasitic groups of fungi are given. It is clear that parasitism, far from being recent and derived from saprophytism, is generally ancient in the fungi; that the Ascomycetes arose from parasitic, aquatic Phycomycetes; and that saprophytism has in general been derived from parasitism.