THE CARE OF STREET-TREES 123 



will be risk of the limb's splitting at the shoulder. In 

 such case begin as before with an undercut, Plate 29, Fig. 2 ; 

 then, in order to utilize the weight of the end of the limb to 

 spread the cut for the clearance of the saw, cut close to the 

 shoulder, about half way through the limb, Plate 29, Fig. 3. 

 Then remove the saw, and cut on top of the limb, a little 

 above the undercut, Plate 29, Fig. 4. When the two saw- 

 cuts meet on the same level, the limb will drop off, Plate 

 29, Fig. 4. Then finish as before, by sawing off the stub. 



The Rule to Follow. — Hence the rule for the proper re- 

 moval of a limb is: Always begin with an undercut about 

 eight or ten inches from the base of the limb you want 

 to remove. Then saw close to the shoulder, as has been 

 pointed out before. When past the centre of the limb, pro- 

 ceed cautiously. If the swelling at the base of the limb is 

 not too great, the limb will split horizontally, turn about the 

 remaining stub as a pivot, and fall off. You can then safely 

 finish the cut. If, however, the chances are that the limb 

 will not split horizontally, but break at the shoulder, saw 

 above the undercut till the limb drops off and then remove 

 the stub. By following the above directions there is no 

 danger of causing injury to the trunk of a tree. 



Healing of Scar. — The time it takes a pruning-scar to 

 heal completely depends upon its size and the rapidity of 

 growth of the tree. A rapidly growing tree, like the Caro- 

 lina poplar, can heal a wound on its trunk, three or four 

 inches in diameter, in one growing season; while it takes 

 a hard maple a few years to accomplish a like result. 

 While the callus is overgrowing the scar from the periphery 

 toward the centre, the end grain of the remaining stub is 

 exposed to the weather. The wood dries and checks, and 

 although all precautions may have been taken to remove 



