THE AMERICAN NATURALIST [Vol. XLVIII 



encing these characters are enumerated and the results 

 are given of the studies made of them. It is noted that 

 the factors are so interrelated that the best conditions for 

 producing one effect are often injurious in some other 

 direction and that the chief problem in orchard manage- 

 ment is a proper balance of the various factors. An 

 ' ' optimum principle ' ' is recognized, according to which 

 plant growth and development increase as the most dis- 

 tant essential factors approach the optimum. The factor 

 farthest from the optimum, therefore, whether below 01 

 above, may control the results from a crop 



Outline of the Experiment 

 Since the season of 1912 was one of full. crop in nearly 

 all centers of apple production, conditions were especially 

 favorable for the study of variation in this fruit. The 

 writer accordingly obtained specimens for study and com- 

 parison grown in a number of localities under quite dis- 

 similar conditions. The method employed was therefore 

 that of Shaw, as pointed out in the last paragraph, rather 

 than that of Stewart. The study has been pretty largely 

 confined to Washington-grown apples, though a few have 

 been obtained for purposes of comparison from the east 

 and middle west. The formal investigation of the prob- 

 lem has been carried on but a single season, which is en- 

 tirely too brief a study to demonstrate conclusively all 

 points touched upon. The conclusions reached, however, 

 are strongly supported by many observations in various 

 localities extending over a number of seasons, and are so 

 suggestive of further lines of study as to justify a report 

 at this time. 



In carrying on this investigation the aim has been to 

 secure as much information as possible regarding the con- 

 ditions under which the fruit was grown. The endeavor 

 has been to get into communication with the growers and 

 obtain from them through correspondence data regarding 

 the character of the soil, rainfall, irrigation, elevation, 

 exposure, temperature, age of trees, fertilization and 



