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 

 strohus 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 hght 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. Eibes diseased with it 

 were found there in 1895 (39, 123), showing it to be established in 

 that locality then. It seems to the ^vriter 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 



