WOUNDS. 475 



starts in the spring, and has ascended to the foliage 

 through the young wood, it is arrested in its back- 

 ward passage by this girdling of the bark of the 

 tree. If the least channel exists upon any side, the 

 tree will often recover ; but if the girdling is entire, 

 certain death results. Field-mice are encouraged 

 by the presence of turf, or any rubbish in the 

 vicinity of the orchard. After deep snows, when 

 other supplies are cut off, they are especially active ; 

 when found, they should be killed if possible, and 

 the snow about the base of the tree trodden hard, 

 to prevent their burrowing. 



11. The j^resetice of Lichens. These give to an 

 orchard a very neglected appearance. Although 

 they are not directly injurious, yet they are so 

 indirectly, by affording harbor for insects. They 

 are also often an index of a poor state of health in 

 the tree. They grow upon the dead bark, which 

 has not been cast off because the vital functions 

 are not sufficiently active, and the tree did not grow 

 fast enough to burst this outer coating. In old 

 trees it may be a proof of decrepitude ; in which 

 case the vigor of the tree can hardly be permanently 

 restored. But, with young trees, it results from 

 some unfavorable condition ; generally the want of 

 thorough drainage and liberal manuring. 



12. The circulation having been vitiated or poisoned 



