No. 4.] TEEE SURGERY. 459 



any but the very smallest wounds. Observation and com- 

 parison led to the following conclusions : — 



1. Wounds on old and decayed trees heal very slowly, 

 for usually these trees are making very little annual growth. 



2. AVounds on young, healthy and vigorous trees heal 

 very rapidly. 



3. In general, wounds near the leaves heal most readily. 

 Those wounds near the top of the tree or the ends of strong, 

 healthy limbs, where the growth of the wood is most rapid, 

 usually show the greatest annual growth. 



4. "Wounds near the base of the tree, and therefore far- 

 thest from the leaves, heal very slowly. 



5. Wounds on the upper side of a limb do not heal at all 

 in many cases. There also the wood is most exposed to the 

 elements, and decays more rapidly than when the wound is 

 made upon the lower surface. Where the face of the wound 

 is nearly level, even if healing begins well, the raised callus 

 growth around the wood may serve to hold the water^on the 

 exposed surface of the wood, thus facilitating wound rot. 



6. Other things being equal, fcAV and small wounds heal 

 best. Thus we approach the final query, — How many and 

 how large limbs can be safely removed from a tree ? 



It is well know^n that foresters and orchardists sometimes 

 remove the entire heads of old trees, leaving only a few 

 small branches or suckers, which shortly form new and vig- 

 orous heads. Willow posts set in the ground are known to 

 send out shoots and send down roots, soon forming a new 

 tree. I have even seen willow logs thrown on damp ground 

 take root and send out shoots ; but it does not follow from 

 this that harsh and vigorous pruning will generally succeed. 



I have never had any experience in heading in old trees, 

 but have not known any wound over four inches in diameter 

 made in general pruning practice to heal in six years. This 

 ought to give the man who casuallj^ hacks oif limbs eight to 

 twelve inches in diameter something to think about. If we 

 remove such limbs, we can hardly expect the wounds to heal 

 in fifteen or twenty years, if ever. In the mean time, the 

 tar or paint weathers ofi", and must be renewed. Cracks 

 appear in the wound's surface ; these must be kept tightly 



