18 BULLETIN 084^ U, S. DEPAETMENT OP 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. Thej^ 

 state — 



From these and numerous otlier 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 developr 

 ment during the following season, even should it survive the winter 

 in a dormant stage. 



