This interesting fungus was first brought to the notice of mycologists in 1889. It was originally collected two years earlier by Dr. W. A. Kellerman at Manhattan, Kansas. It has since been frequently collected from Kansas and Colorado northward and eastward to Manitoba and Wisconsin. Specimens are variously labelled in herbaria under Albugo, Plasmopara, Peronospora and Basidiophora. The fungus is abundant and conspicuous in the field on its single host, Iva xanthifolia Nutt.. The first impression is that of a downy mildew, but a closer view suggests a white rust. The taxonomic position of this fungus has been a puzzle to mycologists. It presents some problems of great morphological and phylogenetic significance. The conidia are borne above the epidermis, on conidiophores quite similar to those of Basidiophora, but grouped into a sorus as in Albugo. This last character distinguished it from the Peronosporaccae while the production of spores singly on the short branches of the conidiophore separate it from Albugo
