INFLUENCE OF HEREDITY 105 



the work of plant improvement brings with it, 

 incidentally, a knowledge of these forces. It is 

 the knowledge of these forces, rather, which 

 makes plant improvement possible. 



There are really, after all, only two main in- 

 fluences which we need to direct, in order to 

 change and control the characteristics of any 

 individual growing thing. 



The first of these is environment. 



Rains, snows, fogs, droughts, heat, cold, 

 winds, the change in temperature between night 

 and day — soil, the location in shade or sun — 

 competition for food, light, air — the neighbors, 

 whether they be plant neighbors, or animal 

 neighbors, or human neighbors — all of these, and 

 a thousand other factors which could be men- 

 tioned, are the elements of environment — some 

 pulling the plant one way and some another, 

 but each with its definite, though sometimes 

 hardly noticeable, influence on the individual 

 plant. 



And the second is heredity! 



Which is the sum of all of the environments 

 of a complex ancestry — back to the beginning. 



Just as with the bear, so in plant life. In 

 every seed that is produced there are stored away 

 the tendencies of centuries and centuries of an- 

 cestry. The seed is but a bundle of tendencies. 



