320 



GENERAL PLANT PATHOLOGY 



regard for shade trees, as they look upon them as obstacles to the 

 prosecution of their work. Improper pruning, when large stubs are 



Fig. 128. — Properly treated area left 

 by branch removal. Scar beginning to 

 heal over by callus growth. (After 

 Collins, F. L., U. S. Yearbook Dept. 

 Agric, 1913-) 



Fig. 129. — Properly treatcil branch 

 scar' about three-quarters healed over. 

 (After Collins, F. L., Yearbook U. S. 

 Dept. Agric, 1913) 



left, is another source of danger to the tree, which with proper knowledge 



can be safeguarded. There are a 



thousand and one details which, if 

 neglected, will work injury to the 

 planted trees. 



Character of the Work. — Tree sur- 

 gery consists in the removal of de- 

 cayed or dead limbs from trees, the 

 cutting ofif of stubs left by improper 

 methods of pruning, and the treat- 

 ment of scars, holes and cavities, so as 

 to prevent decay and secure proper 

 healing (Figs. 128, 129, 130). The 

 removal of branches from trees should 

 be done in such a way as to prevent 

 injury to the surrounding bark and 

 cambium or active layer of growth. 

 For this purpose, a saw, or gouge, a chisel, a mallet and a strong 

 knife are essential. Where the branches are high above the ground, 



Fig. 130. — Cross-section of 7- 

 year old blaze on a quaking aspen 

 nearly healed over. (After Collins, 

 F. L., Yearbook U. S. Dept. Agric. 

 1913-) 



