New York AGRICULTURAL EXPERIMENT STATION. 339 
generally known it will be found in many of the apple growing 
sections of the northern, central, and New England states. 
APPEARANCE OF CANKERED LIMBS. ~ 
When one approaches a diseased tree his attention will be 
attracted to the dark and enlarged sections of the larger limbs. 
A. closer examination shows that the bark is much roughened as 
well as thickened, and in many instances a portion of the wood is 
laid bare. The decaying bark and wood offer a convenient lodg- 
ing place for borers and fungi which aggravate the injury and add 
to its unsightly appearance. The dead bark on many of the 
diseased limbs clings tenaciously to the decaying wood, which 
is a feature that distinguishes this canker from sun scald, since 
with the latter trouble usually the first symptom to be noticed is 
the peeling of the bark from the injured surface. The area of 
bare wood is often small as compared to the extent of swollen 
bark; limbs are frequently seen that for six feet or more of their 
length are covered with rough bark. The progress of the disease 
on such limbs may be marked by numerous pits or scars, show- 
ing where the fungus was able to live until perchance it gained 
entrance to the cambium through some injury, when a serious 
wound was the result. These scars are usually circular in form 
and may be outlined by two or more concentric lines. An exam- 
ple of this form of the disease is shown in Fig. 1 of Plate X XIX, 
where for more than six feet of its length the limb is covered with 
the rough bark or the scars where the bark has become detached. 
The fungus has only reached the cambium and formed a canker 
at a. Fig. 2 of Plate XXX is a larger view of a section of the 
same limb showing the scars more in detail. 
Other instances occur, where, though the bark is much swollen 
and roughened, the fungus has not been able to penetrate to the 
cambium, but has died after a time leaving the scars of its attack, 
aside from which the limb has regained its normal condition. 
The fungus shows a preference for the larger limbs of mature 
trees. Small limbs and young trees are much less frequently 
