4 BULLETIN 957, U. S. DEPARTMENT OF AGRICULTURE. 
Germany, and soon it had spread over the northern countries of 
Europe (91, 92, 93). It seems to the writer that this was an instance 
of the introduction of a foreign disease into Europe and its destruc- 
tive spread over most of that continent (39, 40) . The fact that Pinus 
strobus had been grown extensively in Europe since its introduction 
there in 1705 (5), but was not known to have this disease until about 
1855, in the light of our experience with this and other introduced 
plant diseases in North America, shows that this was a new disease 
which had reached Europe probably years before its discovery. 
Fig. 1.— Outline map of the Old World, showing the approximate distribution of Pinus cembra (oblique 
hatching) and of its variety pumila (vertical hatching) together with the known distribution of Cronar- 
tium ribicola (black dots). Tree distribution furnished by the Forest Service, United States Department 
of Agriculture. 
It is not certain that Cronartium ribicola is a native of the Swiss 
Alps (174). Schellenberg (123), in 1903, found Cronartium ribicola 
on a single 15-year branch of a tree of Pinus cembra about 200 years 
old in the Engadine Valley, Switzerland. He believed that the 
fungus was native there on this host. Yet this is the first known 
finding of the fungus on pine in that region. Bibes diseased with it 
were found there in 1895 (39, 123), showing it to be established in 
that locality then. It seems to the writer that the circumstances 
point plainly to the fungus having come into Switzerland some time 
previously, and that it is not endemic there; else it would have been 
