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THE AMERICAN NATURALIST [Vol. XLVIII 



color at the limit of winter hardiness of the tree. The 

 southern varieties, on the other hand, require for the best 

 development of color a higher summer temperature than 

 is experienced in the northern localities. The Winesap, 

 for example, when grown in Central New York is partly 

 covered with a pale red. At Pullman the majority of 

 varieties color poorly, due at least in part to the cool 

 climate. That the temperature and not the shortness of 

 the season is the factor involved is shown by the fact that 

 most of these varieties color well in central New York 

 which has a season of about the same length though 

 averaging several degrees warmer. 



Cultural conditions may influence the color to a cer- 

 tain degree. In general those processes of orchard man- 

 agement which favor the early maturity of the fruit re- 

 sult in improved color, especially in localities having a 

 short growing season. Pruning and wide planting are 

 regarded as favoring high coloration by admitting light 

 into the tree, though it is possible that in regions where 

 the light is intense these factors may not be of so great 

 importance in their effect upon color as in less sunny loca- 

 tions. Something has been said of the influence of the 

 soil in the discussion of the literature and it has been 

 noted also that studies of the effect of fertilizers upon the 

 color have not yielded satisfactory or uniform results. 

 The influence of iron compounds is worthy of brief dis- 

 cussion in this connection. It seems evident, from the 

 chemical studies which have been made, that the red pig- 

 ment includes iron in its composition. This has some- 

 times been assumed to mean that the chief requirement 

 for highly colored fruit is the presence of plenty of avail- 

 able iron compounds in the soil. As a matter of fact, 

 iron is also necessary to the formation of chlorophyll and 

 most soils contain an abundance of that element for the 

 purpose. From the chemical data compiled by Stewart 5 

 it appears that the ash of the fruit contains a much 



logical to conclude, therefore, that soils containing suffi- 



s Pa. Sta. Eept. for 3910-11. 



