47 



(ions look place last summer in the Hudson River Valley was 

 evidently about the time when the ascospore stage was just be- 

 coming abundant. It is an important matter then to determine 

 the spore stage and the agency responsible for the spread of the 

 fungus before we can hope to advise an efficient and effective con- 

 trol. For example, such precautionary measures as the peeling 

 of logs before allowing them to be moved could be limited to the 

 lime of year when this was necessary and thus obviate a great 

 cos I. 



Likewise the problem as to how the present epidemical char- 

 aHers exhibited by the disease have come about is as far from 

 solution as it was six years ago. The speaker has recently col- 

 lected and examined a fungus indistinguishable from the chest- 

 nut canker disease fungus on dead chestnut bark in several 

 places in Virginia. No case of this fungus attacking living 

 trees was found in the short preliminary examination made near 

 Lynchburg, although several specimens were collected on dead 

 bark of stumps from which trees were cut about two years ago. 

 Also a fungus found in Pennsylvania on white, red and black 

 oak lias great similarity to the canker disease fungus. The pos- 

 sibility of having several strains of the same fungus identical as 

 to microscopic characters, some saprophytic and others causing 

 a virulent disease, is at once puzzling. One of two things has 

 evidently happened, either the host plant has, under existing 

 conditions, been altered in its physiological process enough to 

 change its susceptibility to I his heretofore saprophytic fungus, 

 or I he fungus has developed a parasitic habit independent of 

 any change in the host. Possibly, of course, both factors may 

 have combined to bring about this disease-condition. Prelim- 

 inary investigations carried on by the speaker seem to point to 

 the fact that the susceptibility of the chestnut tree to this fungus 

 depends upon drought conditions; that is a low water content in 

 i he tree. This requires confirmation however by further detailed 

 experiment. Weather conditions causing winter injury as sug- 

 gested by Dr. Clinton may quite possibly be of importance also 

 in this connection, and accurate data concerning past weather 

 conditions and experiments to determine the effect of low temper- 

 ature on the chestnut tree in connection with the production of 

 susceptibility is highly important. 



