138 PRACTICAL TREE REPAIR 



ing is to make a fundamental difference in the tech- 

 nique of filling. It means that all effort to secure 

 vertical rigidity can be abandoned. It means that 

 a filling made up of horizontal layers will perform 

 all the real functions of a filling, while at the same 

 time it will control the formation of the inevitable 

 cracks in the concrete. The " layer system " has 

 been adopted by most tree repair men, although 

 not always with a complete realization of the full 

 significance of the principles which underlie it. 



Justice demands that it be said, however, that 

 in this branch of tree repair, as in most arts and 

 sciences, there are two schools. Some arbori- 

 culturists still insist that the right way is to secure 

 perfect rigidity throughout the concrete filling and 

 perfect adhesion of the filling to the trunk. To 

 the multitude of nails and numerous iron braces 

 once generally in vogue, this school has added an 

 intricate wire web, woven back and forth across 

 the opening of the cavity, and fixed to the wood 

 by a row of staples an inch or so inside of the 

 cambium. Even though these efforts are success- 

 ful in accomplishing their purpose, it is a matter 

 of considerable doubt with the writer whether that 

 purpose is worth accomplishing. Even granting 

 that the filled portion of the trunk can be made 

 perfectly rigid (and that is granting a great deal), 

 it remains to be proved that a rigid trunk is more 

 resistant to storms than an elastic trunk. 



