16 



Mycologia 



and Puccinia extensicola. Aster and Solidago races came to 

 light, not however quite so well stabilized in some instances as 

 with the corresponding Puccinia races, for in one case sowings of 

 teliospores from the same Carex collection were made to grow on 

 both Aster and Solidago. The two species, one of Uromyces, the 

 other* of Puccinia, were subjected to an extensive microscopical 

 study, and no marked differences could be found between their 

 several corresponding spore- forms, except in the septation of the 

 teliospores. This unity of structure had already been observed 

 regarding the aecia and aeciospores when a preliminary culture 

 of the Uromyces was made seven years before. From the 

 microscopical evidence, united with much collateral evidence, the 

 following statement was made in 1:he discussion of 1910, which 

 holds true to the present time : " As the aecia and uredinia of 

 the two groups [of host-races], one under the genus Puccinia 

 and the other under Uromyces, are indistinguishable, and as the 

 teliospores of the Uromyces agree with the one-celled spores of 

 the Puccinia [mesospores] and also with the two-celled spores 

 in all characters except number of cells and consequent length of 

 spore, the former doubtless are morphological races of the latter. 

 Relationship could be shown better by putting all of these forms 

 under one specific name, and designating the several races by 

 varietal names. But in the present state of taxonomy of the 

 rusts it is more convenient to dispose of them under the two 

 genera : Puccinia and Uromyces" 4 



If any further illustration were needed to show that Puccinia 

 and Uromyces were not only parallel genera but actually identical, 

 it was supplied by the cultures of the following year, 191 1. Dur- 

 ing this season successful cultures on Atriplex hastata of both 

 Uromyces Peckianus and Puccinia subnitens, each grown from 

 teliospores on the grass, Distichlis spicata, obtained from widely 

 separated localities, gave rise to aecia that appeared to be indis- 

 tinguishable. A morphological study of these two so-called 

 species has been reported by C. R. Orton in his article on " Cor- 

 relation between Puccinia and Uromyces," 5 in which he finds a 



4 Mycologia 4 : 22. 1912. 



5 Mycologia 4: 199. 1912. 



