14 BULLETIN 684, U. S. DEPARTMENT OF AGRICULTURE. 
Missouri.—Margins of cankers are intact except in the cases of very young 
branches (water sprouts). 
Jonathan.—Cankers are very large on older branches, with small amount of 
cracking at margin. 
Grimes.—Cankers have margins cracked; probably will survive. 
Winesap.—Margins of cankers are somewhat cracked and much roughened; 
probably will not survive. 
Yellow Newtown.—Maregins of cankered areas are separated from bark of 
living portion of branch, and callus is forming. 
On June 26, 1917, the following notes were taken: 
Ben Davis.—Cankered areas irregularly cracked at margins in case of 
younger limbs. Layers of callus are forming. Those on older wood have mar- 
gins intact. Acervuli are abundant. 
York Imperial.Slits have healed over. They are similar to the control slits. 
Missouri.—Margins are irregularly cracked at the sides but not at the ends 
of the cankers. The cracks are not quite so large as in case of the Jonathan 
variety. 
Jonathan.—Margins are cracked at the sides and separated from the living 
bark, from which callus is forming. There is no such separation, however, at 
the ends of the cankered areas. 
Grimes.—Margins are cracked and a callus layer is forming. Acervuli are 
abundant. 
Winesap.—The same as Grimes. 
Yellow Newtown.—Lips of callus nearly meet. The dead bark is nearly all 
shed. The remnants of the old dead bark, however, produced acervuli. and 
spores after 48 hours in moist chamber. The acervuli were very small and the 
spores few. 
By September 19, 1917, the slits on the York Imperial and Yellow 
Newtown were healed over and the dead cankered bark completely 
eliminated. The cankers on the Ben Davis were persisting without 
any apparent change. In the case of the Missouri and the Jonathan 
varieties there was little or no new growth. Layers of callus were 
forming, but the old cankers with their dead bark still persisted. 
The former large lesions on the Grimes were nearly healed over, 
with elimination of most of the old dead bark. The lips of the layers 
of callus were nearly meeting. The Winesap eankers were similar 
to those of the Grimes except that the healing process had not been 
quite so rapid and hence more dead bark remained. In the case of 
all varieties except the York Imperial and Yellow Newtown, the fruit 
below the cankered limbs was infected with bitter-rot. The infected 
areas extended to the lowest limbs and were about 6 feet across. The 
infection was not carried to the fruit of adjacent trees, only the 
fruit of trees in which cankers had been artificially produced being 
affected. This shows how restricted is the dissemination of the dis- 
ease and why it may become localized in certain trees. 
As a result of these experiments it appears that the Ben Davis, 
Missouri, and Jonathan varieties are quite susceptible to the canker 
disease. The Grimes is apparently not quite so susceptible, but is 
