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THE AMERICAN NATURALIST i Vol. XLYIII 



The difference in the development of certain varieties 

 of apples at these places will be noted later. It will be 

 seen that the season opens slightly earlier in Pullman 

 than in Geneva and closes at about the same time. It 

 would appear, therefore, that the better development of 

 most varieties at the latter station is due rather to the 

 higher temperature than to a difference in the length of 

 season. At White Salmon the season is considerably 

 longer than at either of the other stations, while the tem- 

 perature from May to September is intermediate. 



Latitude and altitude are frequently mentioned as im- 

 portant factors in the modification of varieties. These, 

 however, are not primarily factors, but depend for their 

 influence upon the effect of other factors, which in turn are 

 influenced by the location. Differences in altitude espe- 

 cially result in marked changes in climate often in places 

 geographically near together. 



The light relation is of much importance to the fruit 

 grower. It is clearly evident that the development of 

 color in apples is largely dependent upon the sunshine, 

 and quality also may be affected through the production 

 of sugars. Both intensity of insolation and duration of 

 the daylight must receive consideration. In general, trop- 

 ical, arid or alpine situations are characterized by high 

 insolation, while a long period of daylight "luring the sum- 

 mer months is a factor in northern latitudes. 



The effect of atmospheric influences is largely indirect. 

 It has already been noted that the condition of the air 

 may modify the moisture relation through its effect upon 

 transpiration, thus dryness, high temperature, and rar- 

 ification all favor evaportion, and this effect may be in- 

 creased in windy situations. Atmospheric pressure is a 

 factor of importance in high altitudes. 



The soil may be of importance as a factor in causing 

 variation through either its chemical composition or its 

 physical properties. The former leads to a consideration 

 of the influence of fertilization, the latter to the effect of 

 different methods of culture. Here again other factors, 



