No. 574] VARIATION IN THE APPLE 619 



are at the variety optimum for the physiological proc- 

 esses upon which development depends. A departure 

 from this optimum, whether toward a greater or less in- 

 tensity, means a decrease in size, as is observed in ap- 

 proaching either the northern or southern range of a 

 variety. It has been frequently noted, however, that the 

 optimum for growth is not the best combination of fact- 

 ors for the development of certain other desirable char- 

 acters, so that it is well to choose an environment having 

 certain factors in a somewhat less degree of intensity, 

 being content with fruit of fair size but superior in other 

 respects. Since the apple contains about 85 per cent, of 

 moisture it is evident that the water supply is a factor of 

 prime importance in determining size. It is possible by 

 excessive irrigation to force an abnormal growth of the 

 fruit, though always apparently at the expense of text- 

 ure, flavor, and keeping quality. It is evident, then, that 

 if fruit of good quality is expected, irrigation must be 

 moderate in amount, especially with vigorous young 

 trees. Thinning may result in increased size owing to 

 the larger amount of moisture available for each fruit. 

 Temperature and length of season are of importance in 

 determining, respectively, the rapidity of growth and de- 

 gree of development attained. 



Form.— One of the striking features revealed by the 

 study of a number of varieties from several localities is 

 the fact that the modification in shape due to the differ- 

 ence in environment is by no means uniform for the 

 several varieties. Some varieties are quite constant in 

 shape while others are much more plastic in this respect. 

 Moreover, certain varieties are much more easily in- 

 fluenced than others which respond in the same way, 

 while still others respond differently to the same factors. 

 One of the most frequently observed and conspicuous 

 modifications of form consists of the elongation of the 

 axis of the fruit relative to the horizontal diameter. This 

 character has been especially studied, in the case of the 

 Ben Davis, by Shaw, who found the elongation most 

 noticeable in fruit from the northeastern states, the mari- 



