SHADE TREES. 



175 



observed, where injury was reported from the use of this substance, the 

 pathological conditions were due to other causes, and were present pre- 

 vious to the time of the repair work. 



The expense involved in the different methods of treating cavities 

 varies considerably, and it is not well to increase it unnecessarily. How- 

 ever, if a tree is worth treating 

 the work should be done well, 

 and the more costly methods 

 need not be condemned if they 

 achieve superior results. Before 

 an attempt is made to repair a 

 tree a thorough examination 

 should be made, but this is 

 seldom done. Often a consider- 

 able portion of a tree above and 

 below the ground may be dead 

 without the fact being noticeable 

 to the casual observer. A careful 

 examination would reveal the fact 



that the tree is not worth expen- FIG - *!. Bolt passing through a tree with 

 , , , large square washer. A smaller round one, 



represented by the white circle, is a more 



Shaping the Cavity. The shape desirable form to use. 

 of the cavity interior is determined 



largely by the necessary removal of the decayed material. As the decay 

 of the heartwood is usually more extensive than that of the sapwood, the 

 interior dimensions of a cavity are usually greater than those of the 

 orifice or opening. A shoulder is thus formed, and this is of great ad- 

 vantage when cement and other substances are used in filling. In cases 



FIG. 42. Least objectionable method of anchoring 

 guy wires to trees. 



where there is no shoulder, spikes may be driven into the wood or iron 

 bolts used, or grooves in the wood may be chiseled out to anchor the 

 filling substance more thoroughly and to prevent its dislocation. But 

 the shaping of the cavity opening or orifice is most important, the main 

 object in filling a cavity or covering its opening being to direct the callus 



