MISTAKES IN PRUNING. 89 



crop in that field was a good deal better than 

 usual, and the trees bore a small crop of good 

 apples. The season following, however, several of 

 the trees were dead, and in a few years they were 

 all gone. This is an extreme case, but it illustrates 

 the rule that severe pruning usually does more 

 harm than good. This injury occurs in several 

 ways; If large limbs are removed (especially if no 

 waterproof coating is applied to the wound) air 

 and moisture soon permit the germs of decay to 

 enter, and gradually the center of the tree becomes 

 unsound. Tue center of the trunk is not strictly a 

 living part of the tree, but we know that trees 

 whose centers are decayed are usually less vigorous 

 than others. They contain a thiner layer of sap- 

 wood to convey nutriment, and they are probably 

 otherwise defective. 



The removal of large limbs injures the tree also 

 by exposing the body to the rays of the sun, thus 

 often inducing sun-scald or "bark-burn." This 

 injury frequently invites the attacks of borers 

 which work further damage. 



An almost universal effect of pruning is the 

 lowering of the general vitality of the tree. An 

 apparent increase of vigor may manifest itself in 

 the production of water-sprouts and in a somewhat 

 greater growth on the branches which remain, but 

 this iuorease is mainly temporary, and it is well 



