18 BULLETIN 684, U. S. DEPARTMENT OF AGRICULTURE. 
paratively few cankers of any sort in eastern orchards susceptible to 
bitter-rot, and from those which he has found he has never been 
able to isolate the bitter-rot fungus. Pear-blight cankers from Yel- 
low Newtown trees whose fruit had been badly damaged by the dis- 
ease failed to produce fruiting bodies of Glomerella cingulata. 
Blighted limbs of the Ben Davis, York Imperial, Missouri, Jona- 
than, Grimes, Winesap, and Yellow Newtown at Arlington Farm, 
Va., were sprayed on July 18, 1916, with a suspension of conidia in 
distilled water. Three branches of each variety were thus sprayed. 
On August 8 the branches were removed and placed in moist cham- 
bers. On August 10 sparsely fruiting acervuli were found on one 
branch each of Grimes, Jonathan, and Missouri; no signs of the 
fungus could be found on the remaining 18 branches. 
LEAVES. 
While leaves are of little importance as sources of infection and 
the writer has never found the fungus fruiting on them naturally, 
they are able to act at times as harboring places for the fungus. 
Leaves of the Yellow Newtown from Virginia, even when in ap- 
parent health, will often develop acervuli of the fungus if kept in a 
moist chamber for a period of 12 to 36 hours, the leaves themselves 
becoming dark brown. In Arkansas, however, the writer was never 
able to find the fungus in the leaves of any of the varieties examined, 
namely, the Givens, Ben Davis, and Missouri. 
Shear and Wood (15) in 1913 found that leaves of various hosts 
treated as above developed the fruiting bodies of the fungus. .They 
state— 
From these and numerous other experiments of a similar kind performed at 
different times during the year with leaves from other plants, it appears that 
this fungus is quite generally present in the leaves of many plants in a dor- 
mant or innocuous condition awaiting some weakening of the host or other 
favorable condition which may give it an opportunity to develop. 
The writer has many times during the spring and early summer 
examined the fallen leaves of the preceding year in an effort to find the 
fungus either fruiting on their surfaces or living within their tis- 
sues. Such efforts, however, have been uniformly unsuccessful. It 
is possible that the fungus, not being able to gain much headway 
in the living leaf on account of the vitality of the leaf itself, is kept 
from further development after the death of the leaf by the coolness 
of the weather prevalent at that time. Bacteria and molds not so 
sensitive to the cold may enter, however, and deprive the bitter-rot 
fungus of the food necessary for its existence and further develop- 
ment during the following season, even should it survive the winter 
in a dormant stage. 
