144 
FIFTEENTH REPORT. 
previously described, to see if they would shoot their spores. The 
next morning many spores were found in the drops of water con- 
densed on the cover glass; demonstrating that after being removed 
from the trees and left lying on the ground for five months such dis- 
eased twigs are a possible source of infection. Therefore it should 
be recommended that diseased twigs cut from the trees be immediately 
destroyed. 
Michigan Agricultural College. 
