Blister Canker 
19 
surface in order to note the region in which the most active 
growth occurred. Branches were cut off leaving stubs 10 to 
12 inches long and the cut surface evenly inoculated all over. 
Branches were also removed according to the most approved 
methods of pruning and the whole cut surface inoculated. 
As indicated in table 1 no infection occurred from sprayed 
inoculations even when the bark was bruised or shaved. 
Neither did any infection result from inoculations in the 
region of the cambium on current wood. Twenty-six per cent 
of the inoculations made in the xylem of current growth were 
effective. It was noted, however, that infection occurred only 
in twigs where the deepest cuts had been made. It is evident 
that the wound reduced the resistance of the branch, since it 
was noted that this also occurred to some extent on larger 
limbs. Infection took place more readily where the wounded 
surface was comparatively large. 
As shown in the same table the percentage of infections 
increased with the age of the tissue inoculated from the cam- 
bium to four-year-old xylem but there was little difference 
in susceptibility of four and five-year-old xylem. In fact 
the stub and pruning wound inoculations showed that from 
the age of four years on, there was little difference in the sus- 
ceptibility of the wood to infection since infection usually 
started on stubs and pruning wounds quite evenly on all of the 
wood four years old and over, while on the younger wood 
there was a gradual reduction in the number of infections in 
each successive ring of newer tissue. No infection occurred 
in the cambium or outside of it except in very thick bark. In 
a few cases slight indications of infection were found toward 
the outer portion of the bark where inoculations were made 
in the trunk and large limbs, but in all cases the progress of 
the mycelium was so slow that injury from such infections 
is negligible. In no case was the cambium found to be injured. 
A number of different varieties were used in the series 
represented in tables 1, 2, 3, and 4, but the same proportions 
of inoculations with the four inocula and the different tissues 
inoculated were maintained in all cases. 
CONIDIA INOCULATIONS 
A series of inoculations were made with conidia dupli- 
cating every feature of the series made with ascospores. Co- 
nidia recently matured were secured from stromata still pro- 
tected wholly or in part by the covering of bark. None were 
taken from stromata bearing ascospores. 
