32 North American Forests and Forestry 



which influence its progress. These illustrations 

 were designed to impress upon the reader the fact 

 that a forest, left to the undisturbed action of 

 natural forces, does not remain unchanged from 

 century to century, but is different to-day from 

 what it was yesterday, and will be still different to- 

 morrow. As the individual tree lives through 

 various life stages, from infancy to old age, so the 

 forest as a whole matures and grows old. But 

 while the individual, when its limit of age is 

 reached, must die, the forest has the power of con- 

 stantly regenerating itself, so that its continuity 

 may remain unbroken for countless ages. There 

 are, to be sure, certain slow secular changes which 

 may in the long run destroy a forest altogether. 

 Thus the forests growing in the northern half of 

 our continent in tertiary ages were destroyed by 

 the long glacial winter. But that is a matter of 

 many thousands of years. Humanly speaking, 

 there is no reason why a forest, taking its vast ex- 

 tent as a whole, should not live forever. 



Another important principle we have tried to 

 impress by our cursory observations on the inner 

 life of a forest : Multifarious and bewildering as 

 the variety of its life phases is, the forest and the 

 changes constantly going on in it are not the dis- 

 orderly results of accident. In their astonishing 

 complexity they are yet dependent on a few simple 

 laws of nature. To the degree in which we under- 

 stand these and their workings, to that degree we 

 will be able to control their results. As we pro- 



