which were observed constantly to follow the pruner to suck up 

 exuding sap, may have been the direct agent in many cases in 

 transferring the bacteria. The knife itself may convey the dis- 

 ease, as is shown by the following incident: While making 

 inoculations into the body of an apple tree on the Station grounds, 

 I had occasion to remove from near the base a large sprout of 

 several years' growth. ; This I did with my knife which I had but 

 shortly before used to cut bark from a fresh canker. A typical 

 canker soon developed about this pruned stub (Fig. 24). 



Gf a similar nature are infections which occur thru wounds or 

 bruises on the limbs and bodies of trees. These wounds, commonly 

 results of " barking," may be made by careless workmen when 

 plowing or working about the trees or from the gnawing of ani- 

 mals; one of the worst 'animals in Xew York being the woodchuck. 

 A large percentage of such wounds heal over eventually, but 

 frequently thru the agency of insects or other means these wounds 

 serve as infection courts for the canker bacillus. An interesting 

 case of wound infection came under my observation last season 

 In cutting a cankered branch, I accidently " barked " a healthy 

 limb with the cut end of the diseased branch. The tree was not 

 again visited until some weeks later, when a large and actively 

 spreading canker was found to have developed about the abra- 

 sion (Fig. 25). The bacteria were found in abundance in the 

 diseased tissue and pure cultures were secured. 



The wounds or punctures of insects seem to be directly re- 

 sponsible for some of the infections. Sometimes cankers on the 

 bodies of trees cannot be attributed to infection thru blighted 

 shoots, and in some cases these cankers have been traced directly 

 to the wounds made by insects. It is very probable that many of 

 the cankers at the base of young trees originate in wounds made 

 by borers. The bacteria are probably carried to these wounds 

 by flies or other insects which visit these places to feed on the 

 exuding sap and excrement. The infecting agents in the case 

 of crotch cankers have not as yet been definitely determined. 

 It seems likely that insects again are responsible. I have 

 found them repeatedly hiding in the crevices of the dead bark 

 that accumulates in the crotches, and one species seems to feed 

 to some extent on the living tissue in such, places. I have alsn 



