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THE AMERICAN NATURALIST [Vol. XLVIII 



crops and perhaps in a degree to all plant life. For this 

 generalization, which expresses the relationship of char- 

 acters to environmental factors the name " Law of the 

 Optimum " is proposed. 



This law may be stated as follows: For any given 

 variety there is for each character a certain intensity of 

 each essential factor of the environment at which, other 

 conditions remaining the same, that character reaches its 

 highest development. When all essential factors are in a 

 condition of optimum intensity for any character, that 

 character will reach the most perfect development of 

 which it is capable. A modification of the intensity of any 

 snch factor either above or below the optimum will be ac- 

 companied by a less perfect condition of the character 

 concerned. The optimum intensity of a factor may be 

 wide or narrow in its limits and the optimum for one char- 

 acter may or may not overlap the optimum for others. 

 A variety will be at its best when grown in an environ- 

 ment the factors of which are as near as may be to the 

 optimum intensity for all characters. Under such cir- 

 cumstances the variety is in a state of balanced adapta- 

 tion to its environment. If removed from such an en- 

 vironment to one in which certain factors are distant from 

 this state of average optimum intensity for all characters, 

 the equilibrium is destroyed and the variety is thrown 

 into a state of unbalanced adaptation, in which those 

 characters farthest removed from their respective optima 

 are injuriously affected, while others may be bettered by 

 being placed in a combination of factors of an intensity 

 nearer their optima. A discussion of the practical appli- 

 cation of this law and its bearing upon apple culture in 

 the northwest will be deferred for the present and taken 

 up in a later section. 



A COMPAKATIVE STUDY OP THE SAMPLES 



A close study of the various lots of apples used in this 

 experiment brings to light variations in practically all 

 characters. Many, however, are modifications of charac- 



