TREE SURGERY 351 



neath it ; this results in ideal conditions for infection by wood- 

 rotting fungi. 



Reinforced dressings may be used which seem to supply the 

 theoretical advantages sought by capping and yet are not sub- 

 ject to the disadvantages of sheet metals. The wound is first 

 given a thorough coat of the dressing and this is left to dry for 

 a day or two. Then cotton padding an eighth of an inch in 

 thickness is soaked in the dressing and pressed against the wound. 

 It is then trimmed with a sharp knife so as to extend out to the 

 bark and not beyond it. If the padding extended over the bark, 

 it would be pushed off during the process of callus formation. 

 Finally, after a few days, another coat of the dressing is ap- 

 plied. Tar for the first application and asphaltmn for the 

 latter two are recommended. 



Little need be said concerning the method of applying the 

 liquid or semi-liquid dressings. They may be applied with a 

 brush or swab. Dressings which need to be heated, to make 

 them fluid, require a contrivance for this purpose. A tinner's 

 outfit is probably as adaptable as anything. More than one 

 coat of most dressings is desirable and frequent inspections 

 should be made to determine the need of renewing it. 



Lesion Excision 



The removal of diseased or injured tissues may be accom- 

 plished without cutting away the entire affected organ as is 

 done in pruning. Lesion excision is limited to the eradication 

 of diseased bark and wood of the trunk and larger branches. 

 When the cause of the diseased condition is a parasite, it is re- 

 moved along with the affected tissue. Cankers and wood-rots 

 are the two common types of diseases which are controlled by 

 lesion excision. 



Cankers consist, in general, of dead areas of bark. They are 

 more or less definite in outline. In removing the diseased tissue, 



