No. .-)()!] 



543 



late the law of the struggle for existence as the basis for 

 natural selection and the origin of new species. 



My first purpose, I hope, has been accomplished by 

 quoting extracts from Darwin's correspondence. The 

 second still remains. 



There is nothing accidental, in my opinion, in the fact 

 that a forester should be the first to observe the struggle 

 for existence and its bearing upon the development of the 

 new varieties, because there is no other plant society in 

 the world which presents a more striking example of the 

 struggle for existence and of natural selection than the 

 forest. Nowhere else, also, can the law of this process be 

 more fully studied. 



The regular decrease in the number of trees on a given 

 area with increase in age forms one of the earliest obser- 

 vations of the foresters, who, at a time antedating Dar- 

 win, properly gave this process the name of the struggle 

 for existence, the struggle for the necessary growing 

 space. The foresters have discovered the laws governing 

 this process, a process in which almost 95 per cent, of all 

 trees that start life in the stand perish, and in the form 

 of yield tables have expressed it quantitatively, have 

 measured and weighed it. They have shown how this 

 struggle for existence varies with the species, climate, 

 drainage and soil conditions, and age of the stand ; that it 

 is more intense, and consequently the differentiation into 

 dominant and suppressed classes occurs earlier with 

 light-needing species than with shade enduring ones. In 

 a climate most suitable to the species and on favorable 

 situations this struggle again results in more rapid dif- 

 ferentiation into dominant and suppressed trees than 

 when the species grow outside of their optimum range 

 and on poor soils. These are elementary and fundamen- 

 tal facts known to foresters for many years. 



The foresters have not only observed these facts, but 

 they have also furnished an explanation for them. The 

 more favorable the conditions of growth, the greater is 

 the development of the individual trees; the earlier, 



