p*Cl of tf e 



these tree-enemies to open the way for the de- 

 predations of the other. The trees that insects 

 kill quickly become dry and inflammable and 

 ready kindling for the forest fire. On the other 

 hand, the injuries that green trees often receive 

 from forest fires render them most susceptible to 

 the attacks of insects. 



This interrelation almost cooperation 

 between these arch-enemies of the forest was 

 impressed upon me during my early tree stud- 

 ies. One day I enjoyed a splendid forest sea 

 from the summit of a granite crag that pierced 

 this purple expanse. Near the crag a few clumps 

 of trees stood out conspicuous in robes of sear 

 yellow brown. Unable to account for this color- 

 ing of their needles, I went down and looked 

 them over. The trees had recently been killed 

 by insects. They were Western yellow pine, 

 and their needles, changed to greenish yellow, 

 still clung to them. In each clump of these pines 

 there were several stunted or deformed trees, 

 or trees that showed a recent injury. The 

 stunted and injured trees in these clumps were 

 attacked and killed by beetles the summer be- 



i74 



