42 LUTHER BURBANK 



varying external forces to which all life is every- 

 where subjected demand that the inherent inter- 

 nal force shall always be ready to adapt itself 

 or perish. 



The combination and interaction of the innu- 

 merable forces embraced in heredity and environ- 

 ment have given us all our bewildering species 

 and varieties, none of which ever did or ever will 

 remain always constant, for the inherent life 

 force must be pliable, or outside forces will 

 sooner or later extinguish it. Thus adaptability, 

 as well as perseverance, is one of the prime 

 virtues in plant as in human life. 



Plant breeding is the intelligent application 

 of the forces of the human mind in guiding the 

 inherent life forces into useful directions by 

 crossing to make perturbations or variations and 

 new combinations of these forces, and sometimes 

 by radically changing environments, both of 

 which produce somewhat similar results, thus 

 giving a broader field for selection, which again 

 is simply the persistent application of mental 

 force to guide and fix the perturbed life forces 

 in the desired new channels. 



Plant breeding is in its earliest infancy. Its 

 possibilities, and even its fundamental principles, 

 are understood but by few; in the past it has 

 been mostly dabbling with tremendous forces, 



