424 WEAKNESS. 



But if the earth is warm, yet exhausted, the roots 

 do not find sufficient food, and weakness ensues. 



6th. Improper Qnanagement. If the tree has heen 

 planted too deep or too shallow, the roots not 

 properly spread out in planting, the pruning inju- 

 dicious, or the cultivation of the soil during the 

 summer insufficient, the effect will be for the time 

 to weaken the tree, and, it may be, permanently to 

 injure it. 



7th. Accident. Contusion, gnawing by animals, 

 sun-strokes, or cutting the roots severely with the 

 plough, may prevent the tree from becoming vigor- 

 ous. 



But there are many other causes of weakness 

 besides those above mentioned, such as superabun- 

 dant production. Yet weakness is not always the 

 cause of the diseased action, although it may often 

 produce it. But there are multitudes of maladies, 

 where this is only the effect of the disease. A par- 

 asite may have been at work for years, sapping at 

 the life of the tree, before its results are visible 

 weakness. Some insects attack a tree when in 

 full vigor, — the apple-tree caterpillar, or the canker- 

 worm, — and they soon reduce the tree from vigor to 

 debility. 



But we are too much accustomed to consider all 

 insects as our enemies. If they cross our path, our 

 first impulse is to crush them ; if one of them falls 

 upon us, our flesh crawls with repugnance. What 



