Minnesota Plant Diseases. 



269 



tar. In this condition it rests over until spring, when the cup 

 fruiting-bodies are produced. Several cups spring from each 

 spot and each cup is lined, on its inner surface, with a pal- 

 isade of sacs containing eight spores each. Between the sacs 



are numerous sterile fungus threads. Spotted leaves should be 

 collected in the fall and burned to prevent a spread of the dis- 

 ease in the following spring. The formation of the sac spores 

 is thereby effectively prevented. 



