Fern Rusts and Their Aecia

The rusts in general, a well circumscribed and readily recognized group of parasitic fungi, have not yet been assorted under any generally accepted classification, although the process of placing them in genera, families, orders, etc., has been actively proceeding for considerably over a hundred years. There are more than a thousand species of rusts in North America under about eighty genera. So great is the disparity in views between the most capable and advanced thinkers that there is no unanimity regarding what forms may be taken to represent primitive or ancient states, and what the most recent, specialized states. It is the situation the phanerogamic botanists were in before it was decided whether the cone-bearing plants (gymnosperms) were more suitably placed before all other flowering plants, in the middle, or at the end of the series. So long as the mycologists can not agree whether a short cycled form, like Puccinia Xanthii with its single stage and one kind of spores, is representative of rusts in their primitive condition in early geologic times, or a long cycled form, like Puccinia graminis with its several stages and diversity of spores, there is no hope for an acceptable classification of the rusts. If one were so blind as to be unable to tell which was the