88 



very much enlarged, and ready to give up life at any moment. The 

 other, altl'.ough blighted at several places, is throwing out abundant 

 callus, the areas enlarging and containing live bark underneath, and 

 offers every prospect of" hanging on to life. I think there is no doubt 

 but thit it will go through the winter. Even if it should die later on, 

 it gives one an additional period in which to do something else, to 

 bridge graft if it were so desired. Understand, I am not giving this as 

 absolute proof. I am offering it as one of my reasons for believing that 

 a plant does immunize under the influence of an antigen. 



I want also to call attention to the fact that this immunizing busi- 

 ness is not altogether one sided. No sooner is the first dose of antigen 

 thrown in, and its defensive ferment begun to be formed, than the germs 

 themselves get busy and, under the stimulus of the defensive ferment 

 of the chestnut, which now becomes the antigen for the germs, they 

 begin to make a defensive ferment which will enable them to live in the 

 presence of the condition which the tree has set into action. And this 

 is the way it goes. A see-saw back and forth, with "a survival of the 

 fittest." This is the thing that takes place when various chemicals are 

 used as poison. The bugs are continually immunizing themselves 

 against the chemicals, which must in turn be used in increased amounts 

 to protect our plants. To overcome this in the chestnut blight work, it 

 will be necessary to make autogenous antigens from time to time from 

 the then partially immunized fungus, thereby creating a new line of de- 

 structive weapons. This I am aiming to do as necessity demands, in 

 attaining the high degree of immunity in the few selected chestnuts 

 that I have in mind. 



In closing let me state that I still believe I am on the right track. 

 That we have the choice of either waiting as long as the Chinese did to 

 get the mollissima immunized in the natural course through the ages, 

 or injecting an antigen, and reaping the benefits of the resulting im- 

 munity during our own short life. These methods are before us. We 

 can take our choice, not only in the matter of the chestnut blight, but 

 pear blight, black knot in plum, peach yellows, and as many others, if 

 you please, as we may feel disposed to accept. 



