3894 PROF. J. PERCIVAL ON “‘ SILVER-LEAF ” DISEASE. 
This solitary example was sent to me among a batch of 
specimens from a nurseryman, and was only one year old from 
the bud. The bud had been inserted in a stock apparently 
infected with the fungus near the surface of the ground, and the 
strong vigorous shoot (about 4 feet long) developed from the bud 
had every leaf upon it “silvered.” When I received the tree, 
the stock of course had been cut back, and small sporophores of the 
fungus were growing on the outside of the bark. A cross-section 
of the stock, both above and below the inserted branch, showed that 
its wood was completely killed, with the exception of a very thin 
cylinder just inside the cambium. The wood developed from the 
inserted bud was, however, not in the least discoloured, and 
looked quite healthy, although, as previously mentioned, the leaves 
upon it were all “‘ silvered.”’ 
The constant presence of the fungus upon the roots and root- 
stocks of trees suffering from the “silver-leaf” disease justified 
the conclusion that it was in some way responsible for the 
trouble. The complete proof, however, was not obtained until 
this year. 
In the early part of March 1 inoculated some young healthy 
plum-trees of various sorts with soaked pieces of the sporophores 
of Stereum purpureum, obtained from the specimens cultivated 
from diseased roots and also from some blocks of dead wood. A 
T-shaped cut was made through the bark, and after inserting the 
fungus the wound was bound round with bast. The cuts were 
made above ground on one- and two-year old branches, from 18 
inches to 2 feet from the ends. In the first week in May, 7.¢. 
8 or 9 weeks after inoculation, the leaves upon these branches 
exhibited the characteristic silvery appearance. 
It was of especial interest to notice that while the disease 
showed itself above the wound right to the top of the shoot, 
below the wound it only appeared on the leaves of the next bud 
or spur two or three inches away. Moreover, the disease has 
only appeared hitherto (May 19th) on those leaves developed 
from buds which are placed on the same side of the shoot as that 
on which the inoculation was made, the leaves from buds off the 
straight line drawn from the wound to the tip of the shoot being 
normal. From these experiments, and other observations on the 
course of the disease, it would appear that the disturbing cause 
is conducted rapidly in the sap of the plant; other observations 
I have made also support this view. 
