JACKSON: UREDINALES OF OREGON 209 



and aecia on Pseiidotsuga by exposing the foliage to infection from 

 germinating telia on Populiis tremuloides collected in Colorado. Out 

 of four trials, three were successful. No infection was obtained on 

 La fix. 



It is noteworthy in this connection that all of the northw^estern 

 collections have larger spores than specimens from Colorado. The 

 former show spores 20-28 by 24-32 ix while the average of the latter 

 are 16-20 by 19-26 /i. The culture work was conducted with Colorado 

 material, nearly if not all of which was collected in immediate associa- 

 tion with M. albertensis on P. tremuloides. The type of Caeoma 

 occidentale, on the other hand, was collected in British Columbia and 

 has larger spores. It seems entirely possible that the northwestern 

 collections may represent a different species and have genetic relation- 

 ship with some form on Populus other than M. albertensis. 



14. Melampsora arctica Rostr. Medd. Gronland 3: 535. 1888. 

 On Salicaceae: 



Salix Behbiana Sarg. — Sumpter, Baker Co., Aug. 191 5, J. R. 

 Weir, i6y. 



Salix fendleriana And. — Sumpter, Baker Co., June, 1913, J. R. 

 Weir, 8. 



Salix lutea Nutt. — Sumpter, Baker Co., June, 1913, J. R. Weir, 4. 



Salix sitchensis Sanson — Dothan, Douglass Co., Sept. 8, 1914, G. 

 B. Posey, 3342. 



Salix sp. — Scott's, 7 miles from Fort Klamath, Klamath Co., 

 Sept. 20, 1913, E. P. Meinecke, Cr D 6. 



It is with considerable hesitation that the above collections have 

 been referred to this species. Only those collections which have small, 

 rather thin-walled uredospores, accompanied by an abundance of 

 thin-walled, clavate paraphyses, are included. 



Fraser, working with material collected in Nova Scotia (Mycol. 

 4: 187. 1912; 5: 238. 1913), has made a cultural study of this 

 species. He succeeded in obtaining infection on Abies balsamea with 

 production of pycnia and aecia following exposure to germinating 

 telia from Salix discolor. 



15. Melampsora Bigelowii Thum. Mitth. Forstl. Vers. Oest. 2: 37. 



1879. 

 On Pinaceae: I. 



Larix occidentalis Nutt. — Hood River Co., elevation 4000°, July 



23, 1915, 3305, 3365- 

 On Salicaceae: II, III. 



Salix Bebbiana Sarg. — Austin, Grant Co., Aug. 1915, J. R. Weir, 

 162, 163; Sumpter, Baker Co., July 19, 1913, J. R. Weir, 272. 



