1918} WEIR—RAZOUMOFSKYA 29 
isugensis are Tsuga heterophylla, Tsuga canadensis, and Abies 
lastocarpa. So far as the present cultures show, the hemlock 
mistletoe will not infect Pinus, Picea, Larix, and Pseudotsuga. The 
fact that this mistletoe will infect Tsuga canadensis indicates 
the possibility of it becoming a pest in the native regions of other 
species of hemlock and is a condition to be guarded against. 
Conclusion 
Cultures at present indicate that R. campylopoda and R. crypto- 
poda are not identical. Each form may exhibit considerable varia- 
tion, due to geographic loca- 
tion and host. It is shown 
that R. campylopoda will 
infect Pinus resinosa, and 
care must be taken to pre- 
vent it from getting a foot- 
hold in the eastern United 
States. It will also infect 
Pinus sylvestris and P. mon- 
tana, and should be _ pre- 
vented from entering Europe _F'- 19. tsugensis on Tsuga meriensi- 
. ana: staminate (center) and pistillate plants; 
or plantations of these trees mall form; reduced one-half. 
in America. It is also indi- 
cated that the plant known as R. occidentalis abietina is a biological 
form of R. campylopoda. 
R. laricis will infect Larix europea, L. leptolepis, Abies grandis, 
Pinus ponderosa, and P. contorta. All are new hosts for this species 
except the last. The parasite apparently readily infects the 
Japanese and European larch and would be expected to cause serious 
damage to these trees. Abies grandis, Pinus contorta, and P. 
ponderosa are infected with difficulty. This parasite so far as 
known at present is = economic importance only on Larix occi- 
dentalis. 
The mistletoe known under the name R. Douglasii abietina is 
shown to be identical with R. Douglasii and should be written under 
the latter name. R. Douglasii is only of importance on Pseudotsuga 
taxifolia. 
