116 



ELEMENTARY FORESTRY. 



and occasionally longer. They generally close up again when 

 the wood thaws out and during the following summer grow 

 over only to burst open again the next winter. This alternate 

 bursting open and growing over may continue for many 

 years until very conspicuous and peculiar wounds are formed. 

 In such cracks insects and rot-producing fungi find favorable 

 lodging places and as a result trees are seriously injured and 

 are liable to decay in the trunk. Thei-e are no practical reme- 

 dies for such injuries. 



Figure 28. T 



loaded with ice after a~sleet storm. 



Wind. Injuries from wind are common where thinning is 

 done to a great extent at one time about shallow rooted trees, 

 such as Spruce growing on moist soil. These injuries can be 

 avoided only by thinning gradually. In many such cases on 

 timber lands thinning is impracticable and it is^then best to 



