APPLE DISEASES 55 
edges heal more slowly. The edge.of the wound should be 
cut at right angles to the surface of the bark; cuts made 
otherwise will result in a certain amount of dead bark, which 
makes an easy entrance for canker fungi. 
It is a common, but false, belief that some substance may be 
applied to the surface of a wound to accelerate healing. No 
wound-dressing can induce more rapid callus formation, but it 
has been found very desirable and helpful to split the edge of 
the callus each spring, next to the wood, in order to stimulate 
wide spreading of the callus. The rapidity of the healing pro- 
cess depends on the character and position of the wound and 
the time of year when the wound is made, rather than on pro- 
tective coverings. The sole object of coating a cut surface is to 
protect the heart-wood from decay until the new growth, which 
. forms from the growing tissue immediately beneath the bark, 
has had time to develop over the exposed dead wood and pro- 
tect it from decay. The fundamental requirements of a wound 
dressing, then, are that it be a preservative and a preventive. 
It should have antiseptic qualities, and should be fluid, rea- 
sonably inexpensive, and easily prepared and applied; it is 
essential that it give a complete covering; it must be imper- 
vious to air and water, must be durable, and must not injure 
nor kill the tissues nor interfere in any way with the healing 
process. 
Preparations that meet all these requirements are not to be 
obtained. The substances most commonly used are paint, ” 
asphaltum and tars. Paint is an inefficient covering; asphal- 
tum, once applied, gives good protection, but it is more diffi- 
cult to prepare and to apply, especially when it is liquefied by 
heat. Asphaltum is more readily available if it is dissolved 
in gasoline. This combination has been used on apples with 
satisfactory results. 
The writers have used coal-tar for the past three years with 
good success. This is produced in the manufacture of artificial 
