9 6 



Forests and Trees 



with a mixture of Portland cement and sand in proportion 

 of about one to three. This should be mixed with water 



to make a stiff mortar, 

 carefully packed into the 

 cavity, and left smooth 

 on the surface but not 

 projecting. After the 

 cement has set, it is as 

 well to paint the outside 

 to prevent it from ab- 

 sorbing the moisture. 

 The new wood will form 

 around this and in a 

 short time close over it, 

 and the tree may live 

 for years. Figure 16 

 shows a poplar tree that 

 was attacked by a fungus 

 which had caused a de- 

 cayed strip about two 

 feet long and from one 

 to three inches deep. As 

 the tree was needed in 

 its location until the ad- 

 joining elms grew larger, it was decided to try this "tree 

 surgery." The wound is almost covered and the life of the 

 tree has no doubt been prolonged. 



Insect pests are so numerous and so varied that to give 

 many detailed directions would be beyond our present limits. 



FIG. 1 6. A Russian Poplar Which Has 

 Undergone a Surgical Operation. Bran- 

 don Normal School. 



