188 OUTLINES OF FORESTRY. 



the climatic conditions requisite for their growth 

 exist, they cannot appear until such soil is provided. 



Like other forms of creation, the forest is forced 

 to maintain a continual struggle for existence. 



Its enemies may be divided into two classes, 

 namely, animate and inanimate. 



The principal animate enemies of the forest are 

 plants, animals, and man. 



The principal inanimate enemies of the forest 

 are fire, winds, floods, and avalanches. 



The destruction of the forest by fire is generally 

 complete. Though in some cases a small fire may, 

 by destroying the less hardy forms of plant life, 

 increase the growth of certain trees, such, for 

 example, as the pitch-pine, yet, in general, exten- 

 sive forest fires generally so completely remove the 

 forests, that it is often impossible to re-establish 

 them. 



Severe forest fires generally occur during the 

 dry season of the year. The rain which subse- 

 quently falls finds the ground unprotected by any 

 vegetable covering, and, rapidly draining off the 

 surface, carries away much soil. 



The principal causes of forest fires are the camp- 

 fire, the burning of brush, the locomotive spark, 

 the lightning-bolt, and at times, perhaps, the heat- 



