76 BULLETIN 957. TJ. S. DEPARTMENT OF AGRICULTURE. 
It has been possible to learn a little more concerning resistant 
species and varieties of Ribes. Ribes alpinum is found to be immune 
in America, although, it is stated that it takes the blister rust in 
Europe. There does not appear to be any resistant species which 
will take the place of the cultivated R. nigrum (the black currant), 
or of R. odoratum (aureum) (the flowering currant). Among the 
cultivated red currants the varieties Franco-German, London, 
Rivers, and Holland have shown themselves very resistant. In 
generally infected areas these ma}- prove of value to replace the 
more susceptible varieties. 
In the outbreak area at Kittery Point, Me., one of the oldest in 
North America, the infected pines are thickly crowded together and 
mostly range in height from 15 feet upward. The lower branches 
are being suppressed and are dying rapidly from overcrowding. 
Experience has shown that trees and branches attacked by the 
blister rust are weaker than healthy ones and are more apt to die 
from drought and suppression. Posey and Gravatt 57 find that this 
natural suppression of lower branches at Kittery Point has resulted 
in the killing of many entire branches bearing blister-rust cankers 
well out from the trunk of the tree. In such cases the disease in the 
dead branches is killed also. They find that about 15 per cent of the 
trees originally infected have thus recovered from the disease before 
it reached then trunks. As above intimated, this process is probably 
at its height in this area, since suppression of the branches is ap- 
parently at its maximum. 
Experiments in Control in Europe. 
In experimenting with the white-pine blister rust, the European 
investigator has always had a different viewpoint from that of the 
investigator in North America. This has been due to two reasons — 
the disease was possibly native in Europe, certainly in Asia, but was 
introduced into North America; Pinus strohus, the favorite pine host 
for the fungus, is native in North America and introduced into 
Europe. That is, the situation is exactly reversed in every respect 
in North America as compared with Europe. 
The disease is generally considered to have been native in the 
Alps and in the Ural Mountains upon Pinus cembra. It appeared 
in widely separated localities through Northern Europe before plant 
pathology had developed to any extent. That is, organized quaran- 
tines, present methods of spraying, and many other methods now 
used in fighting plant diseases were unknown at that time. The 
fact that the disease was prevalent practically throughout northern 
Europe before it became generally known, showed plainly that it 
was firmlv established throughout that region. This meant that 
3 " Posey, G. B., and Gravatt, G. F. Op. cit. 
