10 FARMERS’ BULLETIN 1641 
sac. Under suitable conditions the sacs escape through the rae of 
the flask. When free the sacs burst in miniature explosions, throw- 
ing the spores into the air. Thus freed the spores are carried by air 
currents often to great dis 
Ficurp 9.—sSpore horns of the chestnut-blight fungus. About six times natural size 
The enormous numbers in which both types of blight spores are 
produced, together with the fact that they are adapted for different 
methods of dissemination, give insight into one aspect of the diffi- 
culty of halting such a foreign invader once it becomes widely estab- 
lished and begins its march, 
