March, 1912.] 
THE CHESTNUT BARK DISEASE. 
219 
EXPLANATION: 
= A// trees dead 
Ill All Trees diseased 
0 Loco! diseased areas 
+ former diseased areas 
Fic. 10.—Map showing distribution of diseased chestnut. The area of gen- 
eral infection in Pennsylvania is much greater than would be indicated by 
this map. 
