482 SCIENCE OF HOME AND COMMUNITY 



from wounds in trees. The cut should be treated, unless 

 it is one of a small branch two inches or less, with coal tar 

 or paint, the tar being preferable. If the wounds are not 

 thus treated, the wood cracks and furnishes a resting place 

 for the spores of disease-producing fungi. In the case of 

 large wounds this treatment should be renewed every two 

 or three years. If the proper care has been given, in the 

 course of a few years the wound will be covered by the 

 growth of the bark around it. 



Tree surgery. It frequently happens that large cavities 

 appear in some part of the tree and threaten the existence of 

 the tree. Tree surgery is the name given to the methods now 

 used to treat these cavities. The principles involved are 

 very similar to those underlying the filling of teeth. First, 

 all decayed and diseased wood must be removed from the 

 cavity. This is done by means of special chisels made for 

 the purpose. Second, the cut surfaces are sterilized in order 

 to kill any germs of disease or decay that may be present. 

 This is done by painting with creosote. Third, the cut sur- 

 faces are waterproofed by painting with coal tar. Fourth, the 

 cavities are filled with cement. In large cavities the cement 

 is put in by sections separated by tar paper, to prevent the 

 cracking of the cement by the bending of the tree in the wind. 

 The edge of the cement is shaped to meet the wood so that 

 it stands at the level of the cambium layer, which grows out 

 over the cement and in time may cover it completely. 



Some trees bear large branches at such angles that there is 

 danger of their splitting down at the crotch. These may be 

 guyed by means of bolts and chains. Holes are bored through 

 the branches and the bolts inserted. If the branches are 

 near together, one bolt may pass through both limbs. If 

 too far apart for this, a bolt with a hook is passed through 

 each branch and these hooks connected by a chain. The 

 method sometimes used of passing bands of iron or wires 

 around the branch girdles it and injures the tree. 



