No. 574] 



605 



in a different kind of development, or in other words a 

 variation. Having- observed the close connection between 

 the characters and the functions of the plant, we may now 

 inquire whether the former maintain a relation to the 

 environment similar to that maintained by the latter. 

 Putting aside generalizations for the present and confin- 

 ing attention to the apple, it is to be noted that both Shaw 

 and Stewart foreshadowed such a relationship in the 

 papers already noted. Neither, however, carried the 

 analysis far enough to formulate a rule of general appli- 

 cation, though Stewart came near doing so. Shaw recog- 

 nized that the highest perfection in any given variety 

 could be attained only under the most favorable summer 

 temperature. Stewart applied this idea to other factors 

 than temperature in his ' 4 optimum principle," which is 

 " that plant growth and development increase as the most 

 distant essential factors approach the optimum." His 

 failure to recognize the connection between the various 

 factors of the environment, on the one hand, and the sepa- 

 rate characters of the apple, on the other, may be ac- 

 counted for by the fact that his investigations dealt only 

 with fruit grown under slightly modified conditions, which 

 resulted only in such slight variations that the independent 

 modification of the separate characters escaped notice. 



In examining various samples of apples produced under 

 the influence of quite dissimilar combinations of environ- 

 mental factors, the writer has many times noted the modi- 

 fication of certain characters more or less independently 

 of others. It is true that characters are often found to 

 vary together through a relationship of direct or inverse 

 correlation. Such cases, however, are possibly as often 

 due to the response of the various characters to the same 

 factor of environment as to any direct connection between 

 the characters, though the latter no doubt exists in many 

 cases. Keeping in mind these facts and also the close 

 relationship of function and character, the writer has 

 formulated a principle which he believes is of general ap- 

 plication not only to apples but to other horticultural 



