696 JOURNAL OF' FORESTRY 



6. Similar degrees of resistance shown by members of the same 

 coppice group (and by branches of the same tree) indicating an in- 

 herent condition. 



Graves then concludes that by working with this native resistant 

 material and by crossing with resistant oriental species, an extremely 

 resistant or practically immune strain of chestnut timber may be 

 developed to replace the blight ravaged areas. A recent article by 

 Collins" supports the resistance conclusion and gives examples of 

 recovery. 



No attempt has been made in the foregoing to cover all the work 

 which has been done on blight resistance but merely enough to show 

 clearly that there is resistance and that it has attracted the attention 

 of investigators. The contribution which the writer of the present 

 article desires to make follows : 



DEVELOPING IMMUNITY 



It seems very clear from the facts now available, viewing the whole 

 chestnut range and considering but a brief period of time, that the 

 blight will sweep over the chestnut areas as a wave and leave nothing 

 but dead trees in the present stand. A few trees left by accident will 

 succumb to later attacks. Then will follow a period of sprouting and 

 killing back of the successive sprouts. Will all these sprouts on all the 

 trees be killed eventually by the blight? On the answer to this ques- 

 tion may hinge the future of American chestnut as a forest type or 

 as an element of practical importance in the forest. It should be 

 kept clearly in view that the coppice group, and not the individual 

 trees or sprouts in it, is the unit. Therefore until the entire group is 

 no longer able to send up sprouts that particular unit is not dead. The 

 first attacks kill all the large trees and merchantable material, and 

 successive repeated attacks have kept and are keeping the sprouts 

 from reaching merchantable size. Consequently, for all practical 

 purposes at present the blight has wrought a complete destruction of 

 the chestnut stands wherever it has approached complete infection. 

 The dead trees continue to sprout at the base and below the point of 

 infection while the smaller stems sprout repeatedly after being killed 

 back by the blight. This increases the length of life of the vegetative 

 unit (the coppice) two or three decades, perhaps, and offers an oppor- 

 tunity for changes to take place between the host plant and the parasite. 



