SHADE TREES. 



177 



(a) Cement cannot accommodate itself to the constant swaying move- 

 ments of trees. As a consequence the fillings are likely to become dis- 

 placed and crack, although this is not so often the case with fillings low 

 in the tree. This unavoidable cracking of the cement renders it extremely 

 unsuitable for use in cavities. 



(6) Cement upon drying shrinks from the wood, furnishing an entrance 

 for water, frost and injurious organisms which may cause damage if the 

 conditions are favorable. 



(c) It is practically impossible to stop bleeding from a cavity that has 

 been filled with cement. This exudating sap or "slimeflux," which is 



FIG. 45. Cross-section of split tree with bolt and 

 countersunk nuts and washers and iron braces to 

 obviate movement. Instead of cement, wooden 

 blocks should be employed to cover the opening of 

 the cavity. 



not uncommon in trees, discolors the bark and in some cases injures the 

 underlying tissue. 



(d) There is nothing to be gained from filling a tree cavity with cement 

 or any material. The chief object of filling is to protect the healing tissue 

 or callus of the tree after the cavity has been thoroughly cleaned and dis- 

 infected, and this can be accomplished by other methods. 



(e) Cement does not in any case strengthen the tree; on the contrary, 

 it often proves weakening because of its cumbersome and quite unneces- 

 sary weight. It is not adapted to horizontal cavities, which are difficult 

 to seal sufficiently to prevent trouble from water, etc. 



(/) The several schemes devised to increase the efficiency of cement 

 fillings, such as re-enforcing with iron, wire, etc., covering the cement 



