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fusea (Pers.) Wint., whose morphological aspects were strikingly similar to 

 those of the Aecidium, i. e., the sori of the two rusts were arranged in the 

 same manner ; the effects on the host plant were the same, and the macro- 

 scopic characters of the two were alike. He concluded that the two forms 

 were closely related phylogenetically. Then his problem was : How find 

 the alternate stage of the Aecidium form? 



On examining the teliospores of the short-cycled form microscopically 

 he found them to possess very striking features, having a roughly warty 

 wall, and being strongly constricted at the septum. A careful examination 

 of his unconnected Puccinias revealed one having spores similar to those of 

 the short-cycled form on Anemone, Puccinia Pruni-spinosce Pers., the plum 

 rust. He cultured the seciospores from Anemone on the leaves of plum and 

 peach trees and grew the uredinia and telia of the plum rust. In his inves- 

 tigations at this time he combined, in this way, five heteroecious species. 

 Three of these species he proved by cultures ; namely, 



1. Puccinia Pruni-spinosce Pers. with Aecidium punctatum Pers. 



2. Uromyces Yeratri (DC.) Schroet. with Aecidium Adenostylis 

 Sydow. 



3. Uromyces Rumicis (Schum.) Wint. with Aecidium Ficariw Pers. 

 The correlation, then, of two rusts of distinct species depends upon 



several things : first the family relationship of the host plants. The rusts 

 are usually on the same or closely allied species of host plants. The macro- 

 scopic characters of the two rusts are also of decided importance. They 

 can usually be expected to have similar effects on the common host plant: 

 and the location and disposition (i. e., whether they are amphigenous, 

 epiphyllous, hypophyllous, caulicolous ; numerous or few, scattered or 

 crowded; circular, oblong or irregular, etc.) of the sori are important 

 factors. 



The most important thing, however, is the agreement of the microscopic 

 characters of the analagous spore forms. The teliospores of the short- 

 cycled and long-cycled forms are compared for thickness, color and mark- 

 ings of the walls; the condition of the apex (thickened or not) ; measure- 

 ments of the spores ; length, color and type of pedicels ; and the general 

 conformation of the spores. 



Owing to the fact that the knowledge of the rust fungi of very many 

 regions is not complete, the geographic distribution can not be considered 

 as extremely important. Nevertheless many interesting comparisons are 

 shown by a study of the distribution of the correlated forms. 



