JACKSON: UREDINALES OF OREGON - 209 
and aecia on Pseudotsuga by exposing the foliage to infection from 
germinating telia on Populus tremuloides collected in Colorado. Out 
of four trials, three were successful. No infection was obtained on 
Larix: 
It is noteworthy in this connection that all of the northwestern 
collections have larger spores than specimens from Colorado. The 
former show spores 20-28 by 24-32 u while the average of the latter 
are 16-20 by 19-26 wp. 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. Grénland 3: 535. 1888. 
ON SALICACEAE: 
Salix Bebbiana Sarg.—Sumpter, Baker Co., Aug. 1915, J. R. 
Weir, 167. 
Salix fendleriana And.—Sumpter, Baker Co., June, 1913, J. R. 
Weir, S. 
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 BIGELOW! Thiim. Mitth. Forstl. Vers. Oest. 2: 37. 
1879. 
On PINACEAE: I. 
Larix occidentalis Nutt.—Hood River Co., elevation 4000°, July 
23, 1915, 3305, 3305. 
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. 
