WHITE-PI XE BLISTER RUST. 7 



lislied in New England, New York, Wisconsin, Minnesota, and 

 Canada. 



It has been known since 1892 that there was a fungus on Kibes in 

 the West much resembling Cronartium rihicola, but until 1917 its 

 alternate stage on pines was unknown. In that year the Office of 

 Investigations in Forest Pathology began work upon this western 

 fungus, which was soon found to have an alternate stage on Pinus 

 edulis and P. monophylla in Colorado and Arizona (50, 114) and was 

 named Cronartium occidentale . Its distribution and that of C. rihi- 

 cola as known to January 1, 1920, is shown on the map (fig. 2). See 

 figures 3 to 12 for the progress of C. rihicola by years from 1909 to 



Fia. 4.— Outline map of the northeastern part of the United States, showing (by black dots) the known 

 (cumulative) distribution of whito-pine blister rust in North America to and including 1910. 



1918, inclusive. Cronartium occidentale is found in localities where 

 it could hardly be an introduction, as the Ute Indian Reservation in 

 southwestern Colorado, where it was found by Bethel in 1897; also 

 in the Mesa Verde region, where no cultivated Ribes or pines have 

 ever been introduced. Rihes aureum is native in the Rocky Mountain 

 region and is a favorite host for Cronartium occidentale as weU as 

 C. rihicola. 



Since Rihes aureum was intimately associated with Cronartium 

 rihicola in its earlier knowTi occurrences in Europe, an inquiry has 

 been made into the possibility of the fungus being American in origin 

 and its being introduced into Europe on R. aureum. when that plant was 

 first sent there. The facts thus far determined arc- that R. aureum 



2 Spaulding, Parley. Ribes aureum not an original host of Cronartium ribicola. In manuscript. To 

 be published in Phytopathology. 



