80 MASSACHUSETTS HORTICULTURAL SOCIETY 



wise, SO far as I have been able to determine. Similarly, if there 

 is any drought effect that produces bark lesions, it would to that 

 extent favor the bark disease. But in general, drought in summer 

 hinders the spread of the bark disease by decreasing or even com- 

 pletely suppressing spore production. The behavior of the fungus 

 in dry weather, particularly its growth on exposed roots and at the 

 base of trees and stumps, especially when the latter are shaded by 

 surrounding herbage, together with its dependence on moisture 

 and rain for dissemination — all shows that it is distinctly a lover 

 of moisture. A comparison of a small number of trees in the green- 

 house grown under dry and moist conditions has shown no essen- 

 tial difference in the spread of the fungus in the trees after it had 

 once gained foothold in the bark; on the other hand, spore pro- 

 duction in the dry greenhouse was completely suppressed, and 

 inoculations difficult to make without special precautions to insure 

 moisture at the point of inoculation. 



I therefore find myself in disagreement with the view that winter 

 injury and drought injury stand in any appreciable causal relation 

 to this disease (18, 19), for the following reasons: 



(1) No evidence has yet been adduced to show that the winters 

 in the past decade have been more severe, or the summers dryer, 

 than in previous decades. 



(2) Evidence is lacking to show that the chestnut has suffered 

 from such injury more than any other native forest tree of the 

 same or similar range. 



(3) Weather conditions have varied locally, and neither winter 

 injury nor drought injury has occurred to fruit trees, for example, 

 over the whole range of the disease. In other words, neither 

 winter injury nor drought conditions, nor both together, are 

 coincident with the range of the bark disease. For example, no 

 State has suffered more from winter injury to fruit trees in recent 

 years than Michigan; yet the bark disease is not known to occur 

 in that State. 



(4) It is difficult to imagine any winter injury, especially if 

 associated with drought, that would leave the roots in a perfectly 

 healthy condition. Practically all trees killed by the bark disease 

 sprout vigorously and repeatedly below the girdled point: this is 

 indeed the most constant and conspicuous character of the disease. 



