356 MANUAL OF TREE DISEASES 



of the concrete must project no further than the sapwood. The 

 callus will then roll over the edge and be supported by the con- 

 crete. The outer surface should be left rough and tar or cement 

 paint used to waterproof the siu-face of the filling. 



When asphaltum is employed, it is generally mixed with sand, 

 sawdust or excelsior. A system of briquettes made of asphalt 

 and sawdust is often used to build up a wall, making the face of 

 the filling. This is laid up as a brick wall is made, each briquette 

 being first dipped in hot asphalt. The briquettes next the edges 

 of the cavity are nailed to the wood. Reinforcing may be 

 adopted as in concrete fillings, and the space behind the bri- 

 quette wall is filled with asphalt mixed with sawdust or sand. 

 Sheet metal may be used instead of the briquettes but it is liable 

 to tear loose with the bending of the tree. 



In all tree surgery work, the ingenuity of the worker is called on 

 to figure out what is best under the existing circumstances. The 

 book, "Practical Tree Repair" by Peets, and an article in the 

 1913 Yearbook of the Department of Agriculture by Collins, give 

 many details of this kind of work which are not included here. 



The fact to be kept in mind, however, is that most tree sm-- 

 gery becomes necessary only because small injuries were not 

 cared for. Proper pruning, wound dressings, bracing, bolting, 

 chaining, guying and all such operations are necessary to pre- 

 vent injuries. , If such points are given attention, very little sur- 

 gical work need be done. 



References 



CoUins, J. F. Practical tree surgery. U. S. Dept. Agr. Yearbook 



1913 : 163-190, pis. 16-22. 1914. 

 Peets, Elbert. ' Practical tree repair, pp. 1-265. (Illustrated.) 1913. 

 Selby, A. D. Dressings for pruning wounds of trees. Ohio Agr. 



Exp. Sta. Giro. 126 : 163-170. 1912. 

 Selby, A. D. Tree fiUings and wound dressings for orchard and 



shade trees. Ohio Agr. Exp. Sta. Circ. 150 : 61-63. 1915. 

 GaskiU, Alfred. The planting and care of shade trees. Forest Park 



Reservation Commission of New Jersey, pp. 1-128, pis. 1-5, 



flgs. 1-43. 1912. 



