No. 4.] TREE SURGERY. 467 



five years' time a considerable bulge in the trunk of each tree 

 had appeared, although the trees were not in any way in- 

 jured. This wifll suggest at once local treatment for wounds 

 that fail to heal. 



Should certain wounds, well situated and properly treated, 

 fail to heal as well as others, let the operator try a rather 

 severe scraping of the bark around the trunk or branch, 

 just where the wound is situated. There is another method 

 which is sometimes helpful. It may happen that the callus 

 forms well around the wound for a year or two, and then 

 seems to stop growth. If its inner edge, where it laps over 

 the face of the wound, is cut away, the cut, by removing 

 the pressure, may cause an increase of callus growth by 

 stimulating the cells to repair the injury. 



Trees which stand Pruning well. 



It is a safe rule never to do any more pruning than we 

 are obliged to do to protect our trees from injury, to render 

 them productive, or to shape them to our ends. Still, 

 where severe pruning becomes necessary, it is well to know 

 what trees will best bear it. 



Of fruit trees, the apple, pear, plum and peach stand 

 pruning well when young or vigorous. Wounds on cherry 

 trees do not heal so readily as on most other fruit trees. 



The ehii, oak, chestnut, locust and ash withstand pruning 

 quite as well as any of our forest trees. While willows 

 heal wounds very readily, their wood decays quickly and 

 needs double protection. The exposed wood of the birches 

 and poplars also rots quickly. Trees which, on account of 

 bleeding, must be pruned in summer, like the maples, birches 

 and hornbeams, must be treated with care ; still, the horn- 

 beams stand pruning well. Trees grown for timber should 

 be planted close together, so that the lower branches may be 

 killed by shade when very small. As the cedars are usually 

 grown for posts, they are seldom pruned. 



