38 LUTHER BURBANK 



with all its acquired habits, the sum of which is 

 heredity; and the numerous complicated exter- 

 nal forces, or environment. To guide the inter- 

 action of these two forces, both of which are 

 only different expressions of the one eternal 

 force, is, and must be, the sole object of the 

 breeder, whether of plants or animals. 



When we look about us on the plants inhabit- 

 ing the earth with ourselves and watch any 

 species day by day, or year by year, we are 

 unable to see any change in some of them. Dur- 

 ing a lifetime, and in some cases, perhaps, in- 

 cluding the full breadth of human history, no 

 remarkable change seems to have occurred. And 

 yet there are to-day few, if any, plant species 

 which have not undergone great, and to a certain 

 extent are undergoing, constant change the 

 invisible changes often appearing abruptly with- 

 out apparent cause. 



The life forces of the plant, in endeavoring 

 to harmonize and adapt the action of its acquired 

 tendencies to its surroundings, may, through 

 many generations, slowly adapt itself to the 

 necessities of existence, yet these same accrued 

 forces may also produce sudden, and to one not 

 acquainted with its past history, most surprising 

 and unaccountable, changes of character. The 

 very existence of the higher orders of plants 



