SOME MODERN ASPECTS OF APPLIED BOTANY 31 
‘Secondly, the introduction of an alien species is desirable if it is 
capable of resisting indigenous diseases, but great care must be exer- 
cised so as not to introduce a new disease along with an alien species. 
An exotic parasitic fungus if introduced may become rampant on 
indigenous species, and, vice versa, an indigenous parasitic fungus is 
equally liable to attack an exotic host... . 
“Tt is therefore quite possible that exotic trees from virgin forests, 
when introduced into a new country and grown under artificial con- 
ditions, may readily become a prey to parasitic fungi, although 
hitherto in their native habitat they may have been entirely free 
from disease of any kind.” 
We are told that in its native habitat the occidental larch is not 
attacked by /eztza Wal/kommit, and here was an example of an 
exotic species becoming the prey of an indigenous fungus, or, I 
should rather say, of a fungus previously introduced from the Conti- 
nent with the European larch. ‘This country was in other words 
the common meeting-ground of an American host plant and a fungus 
disease from the Continent. 
As I had already learned from my former teachers in Munich, 
Professors R. Hartig and von Tubeuf, that such dangers existed, I 
was glad to be able to add this example as a warning in this country. 
How little such warnings are sometimes heeded here and elsewhere 
the following note by Professor von Tubeuf in his Journal, entitled 
‘“* Naturwissenschaftliche Zeitschrift fur Forst- und Landwirtschaft,” 
will show. He says: “In an article published in the Year-Book of 
the German Dentrological Society for the year 1904, p. 156, ] drew 
attention to the danger and frequency of the spread of plant para- 
sites by commerce, not only within a country, but from one country 
to another, and even to distant parts of the world. I also cited 
several instances of such occurrences. The transmission of the rust 
disease of the Weymouth pine within Germany by young infected 
plants was a typical example. 
‘““The news which now comes from America is still more inter- 
esting and significant. This dangerous disease of the Weymouth 
pine has been introduced into America, the home of Prxus strobus, 
with a consignment of seedlings sent from Hamburg. In America 
the disease was unknown and had never been seen there on native 
trees. Every precaution has been taken to prevent the spread of the 
disease, and it is hoped that this invasion may be repulsed as a 
previous appearance of the disease in New York in 1906 was immedi- 
ately stamped out. 
“Tt is difficult to understand why America imports seedlings of 
Pinus strobus in spite of all European experience and warning, 
instead of supplying her own wants by seedlings raised from native 
seeds,” 
Here is a remarkable example:—An American tree is introduced 
into Europe, becomes the victim of a European fungus, and in course 
of time young diseased plants are sent from Europe to America, to 
the imminent danger of the indigenous trees. The loss to America 
