Blister Canker 
21 
The results tabulated in table 2 substantiate those in table 
1 in regard to susceptibility of the various ages of tissue inoc- 
ulated. The much lower percentage of infections indicates 
that the conidia are much less virile than the ascospores or 
that they are more easily inhibited. However, this was to be 
expected from the results of germination tests made in the 
laboratory. 
INFECTED WOOD INOCULATIONS 
The infected wood was secured by sawing out a section 
of a limb two to three feet above the external boundary of 
a well-defined canker. The bark was removed after which 
the wood was sterilized by being immersed in 95 per cent 
alcohol and flamed over a Bunsen burner. A sterilized coarse- 
toothed saw was used to reduce the wood to sawdust which 
was placed in wide-mouthed bottles and slightly moistened. 
The results given in table 3 show a slightly higher percent- 
age of infection than w^as obtained by conidia. In the case of 
inoculations in the older tissues the percentage was decidedly 
higher. This might be due in part to the larger wounds which 
it was necessary to make in order to insert the sawdust, and 
in part to the fact that the fungus was already well established 
in the sawdust. Here again the older wood was found to be 
much more susceptible than the younger tissues. This infec- 
tion by means of diseased wood clearly shows the futility of 
attempting to control canker by cutting away the canker itself, 
as long as any of the mycelium is left in the tree. 
PURE CULTURE INOCULATIONS 
The fungus was transferred from initial cultures to petri 
dishes containing a layer of media several mm. thick in order 
to prevent drying out quickly, and allowed to grow until the 
mycelium covered the surface of the medium in a heavy mat. 
Inoculations were then made by cutting out squares of the 
medium and inserting them in the incisions made in the tree. 
The percentage of effective inoculations was considerably 
higher than when either conidia or infected wood was used but 
not so high as when ascospores were used. As in the three pre- 
viously mentioned series, the older tissues proved much more 
susceptible than those nearer the cambium. No infections 
occurred in current growth except where the xylem was deeply 
cut. In no case did the mycelium penetrate uninjured bark 
even tho the inoculum was placed in direct contact with the 
bark and covered. 
