Morphology of the Spermogonia of the Rust Fungi

Abstract

From a study of 136 spp. in 68 genera it is concluded that the morphology of the spermogonia is phylogenetically significant in the Uredinales. The presence or absence of a bounding structure, the position in the host tissue, and whether growth is determinate or indeterminate are used to distinguish 11 morphological types. Within most genera the spermogonia are constant as to type and related genera have the same or similar types. Three main lines of development of spermogonia are suggested (1) a line including Milesia, Puccinia, and Gymnosporangium, with a strongly convex determinate hymenium; (2) a line including Melampsora, Ravenelia, and Prospodium, with a flat or nearly flat deter -minate hymenium; and (3) a line including Coleosporium, Cronartium, and Phragmidium, with a flat indeterminate hymenium. It is suggested that Ravenelia may have evolved from near Melampsora and Physopella of the Melampsoraceae and given rise, in turn, to Dicheirinia, Diorchidium, Uromycladium, and Hapalophragmium.