July 15, 1915 Wallrothiella A rceuthobii 371 



west. It is apparently the same as that described by Engelmann on 

 spruce from the Sierra Blanca Mountains in northern Arizora under the 

 name " R. douglasii, var. microcarpa." A single collection of what is 

 apparently the same mistletoe on spruce was made from a recently fallen 

 tree on a cutting area near Laclede, Idaho. The parasite was, however, 

 in a healthy condition. The Douglas-fir mistletoe was found in each of 

 the two last-named regions. The fungus material in all the foregoing 

 cases was' very scanty. It is believed, however, that a more protracted 

 search will result in finding the fungus more abundantly on the Douglas- 

 fir mistletoe. 



In order to test the ability of the fungus to attack other mistletoes, 

 infected plants of R. douglasii were bound in contact with pistillate 

 plants of R. americana, the mistletoe of the lodgepole pine (Pinus 

 murrayana). To prevent accident, the experiments were protected by 

 binding cheesecloth loosely about the stem supporting the mistletoe, 

 completely inclosing the plants but not interfering with their vital 

 functions. In all, four such experiments were made during the month 

 of October, 1913. Since pollination had already taken place in the 

 early spring, it was inferred that the fruits of the lodgepole-pine 

 mistletoe would mature normally if infection did not occur. In order to 

 have fully mature plants on the same stem for purposes of comparison, 

 small tufts just below the inclosed ones were shielded by a circular piece 

 of thick white cloth tied just above the tuft and hanging down in the 

 form of a loose umbrella. This would not prohibit the circulating spores 

 from coming up under the shield, provided they escaped from the cheese- 

 cloth net, but would lessen the chances of inoculation. Furthermore, 

 owing to ascending air currents, spores of fungi usually travel upward 

 or at least not directly downward when starting from an elevated point. 

 Other experiments were initiated on the lodgepole-pine mistletoe by 

 crushing in water a number of mature perithecia and thoroughly spray- 

 ing the mixture containing spores over a few pistillate plants. To pre- 

 vent the plants being knocked off during the winter, they were also pro- 

 tected by cheesecloth. These experiments were visited in the latter part 

 of November, 1914. The results were positive. As shown in Plate LV, 

 figure 5, not only had the fruits of the lodgepole-pine mistletoe which 

 were inclosed with the infected plants from the Douglas fir become 

 infected but very thoroughly so. Every fruit bore at its apex the little 

 shiny black tufts of the perithecia of the fungus. One fruit shown to 

 the right in the middle figure of the sprayed plants seemed to have escaped 

 early infection and to have attained nearly a normal size, but, neverthe- 

 less, succumbed to the parasite. The tufts of mistletoe just below the 

 infected ones, which were shielded from above, did not become infected 

 and produced normal mature seeds, which were being expelled at the time 

 the experiments were discontinued. The perithecia of the fungus on 



