1918] WEIR—RAZOUMOFSKYA : 31 
R. americana will infect both hard and soft pines, the latter 
with difficulty, and is of importance only on Pinus contorta and 
P. Banksiana of the former group. This mistletoe will infect 
Pinus montana and may be of consequence if introduced into 
Europe. 
R. tsugensis will infect Abies lasiocarpa, thus possibly explain- 
ing the position of certain rare plants occasionally found on Abies 
in the vicinity of the hemlock mistletoe. This parasite will infect 
Tsuga canadensis and would probably cause serious damage to this 
tree in the East. 
Cultures show very clearly that many of the characters employed 
in the classification of the false mistletoes vary with change of host, 
geographical location, and with various other environmental 
factors. This indicates that only the broader and plainly evident 
lines of demarcation should be employed in their classification. 
OFFICE OF INVESTIGATION IN FoREST PATHOLOGY 
UREAU OF PLANT INDUSTRY 
Missouta, Mont. 
