58 



the amount of chlorophyll in the leaves, in order to find out 

 whether or not such variations as this might increase the immu- 

 nity of a healthy tree. Under the head of preventive treatment 

 is also to be considered the care of wounds, etc. This subject 

 will be fully considered in this conference by other speakers. 

 My own work in this direction is confined to the testing of 

 "washes" submitted to the Pennsylvania Commission for trial. 



If the question of preventive treatment is still so far from be- 

 ing satisfactorily answered, that of a curative treatment is in 

 a more inchoate condition. At most, I can describe the meth- 

 ods adopted in the Pennsylvania Commission laboratory, and in 

 which I shall attempt gradually to start experiments along the 

 following lines: Experiments to test the relative vitality of the 

 mycelium of the fungus, its ascospores and the conidiospores 

 found in summer and those formed on wood during the winter; 

 injection into trees of chemicals toxic to the fungus causing the 

 blight; tests as to the immunity of different varieties of trees. 

 I have started some experiments along two of these lines, but 

 none is completed. According to my experiments so far, the 

 ascospores or winter spores seem to have the greater vitality; 

 then follow the summer or conidiospores. The mycelium and 

 those conidiospores grown on wood seem to be equally suscep- 

 tible to poisons. The injection experiments which are to be 

 made are those where chemicals are -injected into roots and 

 where hypodermic injections are made on the trunks of the 

 trees. These are of necessity dependent on the experiments 

 leading to the discovery of chemicals toxic to the fungus and 

 not deadly to the tree. . 



Experiments as to relative immunity of chestnuts are now 

 being conducted on two or three varieties of trees. Japanese 

 and American trees have been inoculated with the blight. For 

 the purpose of such experimentation, the Commission has been 

 given the privileges of the Botanical Laboratory of the Uni- 

 versity of Pennsylvania, where a special room has been set 

 aside for my work. A greenhouse has been recently completed, 

 in which a number of small chestnut trees are now growing. 



THE CHAIRMAN: The next paper is entitled "Treatment 

 of Individual Trees/' by Professor J. Franklin Collins, United 

 States Department of Agriculture. 



