332 



Bulletin 256. 



Tree surgery. Systematic pruning and tree surgery are very closely 

 related. Tree surgery includes the intelligent protection of all me- 

 chanical injuries and cavities. Pruning requires a previous intimate 

 knowledge of the habits of growth of trees; surgery, on the other hand, 

 requires in addition a knowledge of the best methods for making cavi- 

 ties air-tight and preventing decay (Fig. 252). The filling of cavities in 



trees has not been practiced sufficiently 

 long to warrant making a definite state- 

 ment as to the permanent success or failure 

 of the operation; the work is still in an 

 experimental stage. The caring for cavi- 

 ties in trees must be urged as the only 

 means of preserving affected specimens, 

 and the preservation of many noble speci- 

 mens has been at least temporarily assured 

 through the efforts of those practicing this 

 kind of work. 



Successful operation depends on two im- 

 portant factors: first, that all decayed parts 

 of the cavity be wholly removed and the 

 exposed surface thoroughly washed with 

 an antiseptic; second, that the cavity, when 

 filled, must be air-tight and hermetically 

 sealed, if possible. Trees are treated as fol- 

 lows: The cavity is thoroughly cleaned by 

 removing all decayed wood and washing 

 the interior surface with a solution of cop- 

 per sulfate and lime, in order to destroy 

 any fungi that may remain. The edges of 



the cavitv are cut smooth in order to allow 

 Fig. 2=5?. — ,4 cavity in the pro- . \-u £ j-i. t,- r^ ^1 



cess of being^ filled; rubble ma- free growth of the cambium after the cav- 



sonry or brick being used for ity is filled (see Fig. 253). Any antiseptic, 



the outer wall of the concrete g^^j^ ^5 corrosive sublimate, creosote, or 



filling. . 



even pamt, may answer the purpose; creo- 

 sote,, however, possesses the most penetrating powers of any. The 

 method of filling the cavities depends to a great extent on their size 

 and form. Very large cavities with great openings, are generally 

 bricked on the outside, over the opening, and filled on the inside 

 with concrete, the brick serving the purpose of a retaining wall 

 to hold the concrete in place. Concrete used for the main filling 

 is usually made in the proportion of one part good portland 



