Callusing and Repairing 



91 



Fig. 21. 



Malleable pruning 

 shears. 



applied, while in spring the oozing sap of many species will 

 prevent the paint from sticking or the tar from penetrating. 

 If pruned in the fall, the wound wood begins to form in 

 the early spring and is well advanced before the fungus 

 spores begin to fly. The com- 

 parative absence of fungus 

 spores in late fall and the fact 

 that the form of the tree is 

 better visible when the foHage 

 has left it also favors this season 

 as compared with the summer. Only those species, 

 wliich, like the maples and birches, are apt to bleed freely 

 even late in the autumn and early in spring, are best pruned 

 in winter or late summer, although the bleeding is in the '^ 

 main detrimental only because it prevents the paint from •*' 

 adhering. 



Callusing and Repairing. We will now briefly look at 

 the healing process, a knowledge of which will be useful 

 to the pruner and will assist his judgment, especially as to 

 where and how to locate most advantageously the cut 

 in trimming, pruning, and repairing. 



When, in the natural order of things, a leaf falls, or a 

 piece of bark is sloughed off, as is so conspicuously done 



in the sycamore, this loss of parts 

 has been gradually prepared for 

 and the wound is already cov- 

 ered securely by a cork la}'er, or 

 a temporary covering has at 

 least been pro\'ided for by the 

 formation of gum or resin, before this final voluntary loss 

 occurs. When an involuntary physical injury, as the tearing 

 ott of a piece of live bark or the breaking of a branch, takes 

 place, a similar process of pro\iding a covering of the wound 



Fig. 22. — Sheep shearing 

 shears. 



