164 A NEW THEORY OF EVOLUTION. 



constituents of plant food that a sufficient 

 supply was not left to retain the ascendancy 

 for the same kind of tree, and Nature auto- 

 matically selected another variety that re- 

 quired less of the elements exhausted by 

 the former crop, and whose seeds were no 

 doubt lying dormant in the soil. 



It thus appears that Nature's method 

 of evolution is, when available resources 

 become more abundant, not to develop an 

 existing animal or plant into a new species, 

 but to supplant it by another more highly 

 organised. 



