25 



September, 1889, F. W. Anderson ; and also on related species of 

 hosts from Colorado and Utah northward in the Rocky Moun- 

 tains. 



Of the rose rusts in North America belonging to the restricted 

 genus PlLraginidiiun there are now to be recognized six valid 

 species, all indigenous but one. Space does not permit, and the 

 needs of this discussion do not require the full characterization 

 to be. given for each species, but the following key, when taken in 

 connection with hosts and geographical data, will provide some 

 aid to those persons who desire to determine their collections. 



Teliospores slender, 8-1 i-celled. 



Walls of aecio- and urediniospores thin, l-l-S ;"• 



Teliospores long, 80— ioO|«. I, P. ame7'icamim Diet. 



Teliospores very long, 90-130 /i. 2. P. Rosae-seiigei-ae D'lei. 



Walls of aecio- and urediniospores thick, 2-3//. 



Teliospores long, 90-112^. 3. P. Rosae-ca/ifornic-ae Y)\t\.. 



Teliospores stout, 5-9-celled. 



Walls of aecio- and urediniospores medium, 1.5-2 /i. 



Teliospores 5-8-celled. 4. P. Rosae-arkansa7iae Diet. 



Teliospores 6-9-ceIled. 5- P- n'ontivaguni Arth. 



Walls of aecio- and urediniospores thick, 2-3 ,«. 



Teliospores 5-7-celled. 6. P. discijloyuin (Tode) James 



These six species oi Phragniiduun have a most interesting dis- 

 tribution, both as to hosts and territory. The one species coming 

 from Europe occurs chiefly upon thick-leaved roses of the dog 

 and cabbage rose sections, Rosa canina and R. Gallica, their 

 allies and hybrids, and appears to follow wherever these roses 

 are cultivated. It is known throughout the United States from 

 the Atlantic to the Pacific, northward into Canada, and south- 

 ward into Mexico and Central America. It does not appear to 

 have passed over to any native rose. 



The distribution of the five indigenous species is shown by the 

 accompanying chart. P. aniericaniiin inhabits the northeastern 

 region along the Atlantic coast from Maryland northward and 

 north of the great lakes, chiefly on Rosa hlanda, R. liicida, R. 

 Sayi, and certain cultivated varieties derived from these. P. 

 Rosae-setigerae is only known upon Rosa setigera and R. Carolina, 

 extending nearly throughout the region of the hosts from central 

 New York to central Nebraska. P. Rosac-arkansanaex'i only known 



