PUSTULES IN CRACKS OF BARK. 
When the pustule attacks a large limb or the trunk, there is little obvious change in the 
external appearance of the bark itself, but the pustules show in the cracks of the bark, 
as can be clearly seen in this photograph. The bark often sounds hollow when tapped. 
The fungus continues to grow after the trunk is girdled, sometimes covering the entire 
surface With reddish-brown pustules, which produce the type of spores called ascospores. 
(Figure 7.) 
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