torrp:ya 



February, 1909 

 Vol. 9. No. 2. 



NORTH AMERICAN ROSE RUSTS* 

 By J. C. Arthur 



From the days of Schvveinitz, that is, the times of the first 

 studies of American fungi, down to the near present, all rusts 

 upon roses in North America had been placed under two species, 

 i. e., Phragmidmm speciosum, a strictly American form, and P. 

 subcorticuim, a cosmopolitan form. The latter name has many 

 synonyms, P. tnucronatiiin having been especially popular, but the 

 earliest and consequently the rightful name appears to be P. dis- 

 cifloriim, and therefore will be used in this paper. 



In 1876 Peck vaguely called attention in his twenty-eighth 

 Report of the Botanist of the New York State Musuem (page 86) 

 to a variation in teliospores that he had observed. His words 

 are " American specimens generally have the spores more opaque, 

 and with two or three more septa than the typical form. This 

 variant form might be called var. Americanuniy The variety 

 was placed under P. mucronatimi. Two years ago Dietel pub- 

 lished an extended taxonomic study of the genus PJiragniidhun 

 in Hedwigia, and five months later a supplementary article in the 

 same journal (44: 1 12-132, 330-346)., In these two articles 

 Dietel established and well defined four new species of Phrag- 

 7mdi2i7n mhahiting American roses, and one new species of Caeoina, 

 C. Rosae-gyimiocarpae , from California. This comprises all im- 

 portant taxonomic work upon rose rusts of America up to the 

 present time. 



In pursuing the study of American rusts for systematic pres- 

 entation in the forthcoming North American Flora the genus 

 Phragmidium has been reached, and I desire to give in this 



* Read before the Botanists of the Central States, at the Madison meeting, 

 March 29, 1907. Illustrated with the aid of the McManes fund. 

 [No. I, Vol. 9, of ToKRKYA, comprising pages I-20, was issued January 26, 1909.] 



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