8 BULLETIN 684, U. S. DEPARTMENT OF AGRICULTURE. 
two weeks a distinct callous layer had formed under the edges of the control 
slits. The two callous layers joined after six to eight weeks and occluded . 
the wound. In the slits where bitter-rot spores had been inserted the callous 
formation was less marked. The exposed wood turned dark, almost black, 
and the exposed edges of the bark turned back. The living bark then began 
to dry out gradually and became depressed, and after about two months a 
decided, sharply defined depressed area had formed, with the slit in the center. 
Shortly thereafter small black pustules broke through the dried bark in a 
number of instances. By that time the infected points showed all the char- 
acteristics of small cankers. On examination the black pustules were found 
to contain masses of spores resembling those of the bitter-rot fungus. 
Alwood (1) in 1902, while admitting that cankers may be the 
chief sources of infection in Illinois and Missouri, as stated by Bur- 
rill and Blair (4) and by Von Schrenk and Spaulding (18), did not 
think that these statements applied-in Virginia. He stated— 
In no instance have we been able to find the presence of the bitter-rot fungus 
on the limbs or trunks of apple or pear, though we have especially watched for 
its occurrence. 
Scott (14) in 1906 made the following statements: 
Limb cankers occur abundantly in Virginia orchards, but the writer has so 
far been unable to find the bitter-rot fungus associated with any of them 
5 in no case was there found associated with such outbreaks any can- 
kers that could be identified as bitter-rot cankers. 
Burrill (8) in 1907 stated that a wound is necessary for the begin- 
ning of a canker and that cankers may live sometimes for two or 
even three years. 
The writer (10) in 1915, reporting on work carried on in Arkansas, 
stated— 
On May 15, a cankered limb from the second orchard was brought into the 
laboratory and kept in a moist chamber for 24 hours. This canker resembled 
in every way the limb cankers as described and figured by Burrill and Blair and 
Von Schrenk and Spaulding. It was a black, sunken oval area with many 
Slight rifts or cracks in the bark through which, after the limb had remained 
in a moist chamber for 24 hours, an abundance of the characteristic pink acer- 
vuli appeared. Near the center of this canker was a small dead spur through 
which infection probably took place. Cankers resembling in every way pub- 
lished descriptions and figures of bitter-rot were also collected on June 3 and 
- many times thereafter. 
Previous to his experiences with bitter-rot cankers in Arkansas, 
the writer had attempted at various times to find them in Virginia, 
but without success. Thinking that his familiarity with the appear- 
ance of the cankers in the West might aid him in the search, he again 
attempted to find them in Virginia in 1916 but was unsuccessful. 
It seems therefore rather well demonstrated that whereas bitter- 
rot cankers are of quite common occurrence in the Middle West, 
they are rarely to be found or are wholly wanting in the East. The 
