DISEASES OF THE CHESTNUT AND OTHER TREES. 

 By Dr. Haven Metcalf, Washington, D. C. 



Delivered before the Society, February 17, 1912. 



The John Lewis Russell Lecture. 



The principle of conservation of forests has been so thoroughly 

 discussed, and at least the major lines of activity for the next 

 few years so thoroughly laid out, that this question needs no dis- 

 cussion even by way of introduction. Under American con- 

 ditions the most important feature in the care of forests is forest 

 protection, and this subject falls mainly into three divisions: 

 protection against fire, against insects, and against fungous and 

 other diseases. If we extend our survey beyond the living forest 

 and take into account the decay of timber, due probably wholly to 

 fungi (although the role of bacteria in this regard is practically 

 uninvestigated) we see that we have an enormous field of investi- 

 gation and that the activity of fungi is in the long run respon- 

 sible for the deterioration of more property than the forest fire 

 itself. The preservative treatment of timber as it is being evolved 

 in commercial hands and under the leadership of such an organi- 

 zation as the Forest Products Laboratory, maintained by the 

 United States Forest Service at Madison, Wis., is solving the 

 problem of the control of timber decay in a practical way. The 

 pathological aspects of this work are of great interest (1, 2) and 

 are being made the subject of continuous investigation. 



Preventive Forest Pathology. 



In forest pathology we have to deal with trees under two cul- 

 tural types : first, the trees in the forest ; second, shade, ornamental, 

 and park trees. When we come to consider the question of com- 



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