SHADE TREES. 165 



wounds are located along the line of transference of the plastic substance 

 that they develop healing tissue. The sides of a circular wound as a 

 rule heal over most rapidly because they are most directly in the chan- 

 nels of the transference of the plastic substances, and the top and 

 bottom of the wound heal more slowly. When these facts are borne 

 in mind it will be seen that a proper shaping of the wound is im- 

 portant for the development of a more or less even callus formation. (See 

 Fig. 25.) Cuts made near large, leafy branches are more likely to heal 

 quickly than those near small ones, for the reason that a larger amount 

 of the plastic materials is available. 



To facilitate healing, recourse is occasionally made to cutting the bark 

 smooth around the stumps of the removed limbs, and it is also claimed 

 that after the callus is well started a recutting of the surface stimulates 

 its growth. 



Moisture is said to stimulate the growth of the callus, and the old 

 practice of covering the wound with a mixture of cow manure, clay and 

 lime had this object in view. 



Disinfectants for Wounds and Cavities. 

 There are many erroneous ideas concerning the effectiveness of dis- 

 infectants and their use in general. This is particularly true of disinfect- 

 ing materials used in tree work. Because a certain disinfectant is used 



Fig. 26. — Effects of antiseptic treatment of wood in soil two years: 

 (a) treated with Carbolineum; (Z<) creosote; (c) untreated. Little 

 difference between (a) and (6) ; in (c) practically all decayed and 

 about 50 per cent, completely. 



successfully for one purpose it does not follow that it is applicable to all. 

 As a matter of fact, all disinfectants are limited in their usefulness owing 

 to the great variation existing in organisms as regards amenability to 

 treatment by chemical substances. Disinfectants, therefore, possess 

 specific rather than general properties, which are determined by many 

 different factors. Copper sulfate, for example, is remarkably effective 



