370 Journal of Agricultural Research voi. iv. No. 4 



HOSTS 



The interest arising from the remarkable habit of this fungus of attack- 

 ing and destroying the immature fruits of Razoumojskya pusilla (Peck) 

 Kuntze (Arceuthobium pusillum Peck) on the eastern black spruce {Picea 

 mariana) has led the writer to search most diligently for it on western 

 species of Razoumofskya. The fungus was not found in any region of 

 the Great Lakes States, although the mistletoe of the spruce was abun- 

 dant and much material was examined. In the West the search has been 

 more successful. The fungus was first collected on Razoumofskya doug- 

 lasii Englm. (PI. LV, fig. i) in the vicinity of Como Lake in the Bitter- 

 root Mountains, Montana. The only tree found bearing infected plants 

 stood in a clump of "left-overs" on a cutting area of the Latchem Lumber 

 Co. The mistletoe is so very abundant in this region and suppresses 

 the Douglas fir {Pseudotsuga taxifolia) to such an extent that this tree, 

 according to Supervisor White, of the Bitterroot National Forest, is 

 sometimes omitted altogether from the estimate of the prospective cut. 

 Practically the same conditions prevail throughout the entire Bitterroot 

 and Missoula River Valleys and adjacent regions. It has always been 

 a rule of the writer, in regions of a heavy infection by R. douglasii, to 

 look for the small, closely related mistletoe designated by Engelmann 

 "Razoumofskya douglasii, var. abietina," on Abies grandis and A. lasio- 

 carpa. Experience has shown that this mistletoe is more likely to occur 

 when its hosts are in the vicinity of the Douglas-fir mistletoe. Whatever 

 conclusions may be drawn from this as to the probable relationship of 

 the mistletoe on Abies spp. with the one on Pseudotsuga spp., the surmises 

 as to the presence of the former were correct in the present instance. 



The mistletoe was discovered once on A . grandis by the large spreading 

 or upright brooms. The tree, standing not more than 100 feet from a 

 Douglas fir which supported three immense brooms of R. douglasii,^ 

 was felled and the mistletoe plants carefully examined. A few of the 

 plants, which were pistillate, were found to be infected by W. arceuthobii 

 (PI. LV, fig. 2). On another portion of the same area the fungus was 

 discovered on a few plants (PI. LV, fig. 3) growing deep within a large 

 broom on A. lasiocarpa. Two other mistletoe-infected trees of this spe- 

 cies were cut, all that were found in the region, but the parasite was not 

 attacked by the fungus. A search in other sections of the Bitterroot 

 Valley resulted in finding the mistletoe on the grand and alpine firs, but 

 the fungus was not present. At the head of Rattlesnake Creek, a small 

 stream flowing into the Missoula River at Missoula, the fungus was dis- 

 covered on a small mistletoe (PI. LV, fig. 4) growing on Picea engelmanni. 

 This is the first report of a mistletoe occurring on a spruce in the North- 



1 The brooms caused by this mistletoe are sometimes very large and frequently cause the death of the 

 entire crown above. The infections of no other mistletoe initiate greater and more frequent brooming than 

 do those of R. douglasii. For this reason it is one of the most serious parasites of the entire genus. 



