56 THE LARCH CANKER 
indication of being suppressed. The trees were cut down 
and the parts containing the cankers were brought into 
the laboratory. Here the cankers were sawn through 
transversely and the surfaces planed or smoothed with 
a sharp knife until the section was reached where the 
cambium had first been killed. 
The inspection of these cankers confirmed the two 
important observations that in the large bulk of cases : 
(i) The cankers had been initiated at the bases of lateral 
branches. 
(ii) The cankers were initiated when the sections of stem 
were from three (occasionally two) to eight (occasionally 
nine) years old. 
We must thus consider in detail the condition of affairs 
which exists at the bases of lateral branches on those parts 
of the tree which are from two to nine years old. 
In an ordinary ten-year-old larch plot planted at 3 x 
3 ft., the weaker shoots die off when two or three years old, 
the stronger shoots when five, six, or even eight years old. 
In younger plantations, before the branches have begun 
to shade each other, all of them may remain alive, but 
generally some small dead branches will be found at the 
base of the trunk, especially when they have been smothered 
by rank grass and weeds. Thus the part of the tree which 
is from two to eight years old, in which cankers are generally 
initiated, is also that part where some or all of the lateral 
branches have lately died. Further, in nearly all woods 
the lateral branches become infected with Dasyscypha 
calycina, which grows saprophytically on them as soon as 
they are dead, and continues to flourish on them for three or 
more years, filling all the dead bark with its mycelium. 
When a dead branch is seen projecting from a canker it 
has generally been supposed that the canker has killed the 
branch, but it may equally be true that the fungus spreads 
from the dead branch and causes the canker. In order to 
determine this it was necessary to notice the relative times 
at which the branch died and the canker was initiated. 
The date of the death of the branch may readily be deter 
