444 THE APPLE 



scored an average of 85 per cent out of a possible 100 per cent. In 

 an orchard in which sod mulch was used the color averaged about 

 82.5 per cent. Clean-tillage fruit averaged 75^ per cent, and or- 

 chards treated by tillage and cover crops showed about 75 per cent. 



These experiments seem to bear out the observations of practi- 

 cal growers that there is an increase in the color of fruit grown 

 in sod orchards and a decrease as the cultivation of the soil is 

 intensified. 



Influence of light on color. In apples there are but two colors 

 to be considered — yellow and red. Physiologically, yellow is con- 

 nected with colored bodies in the superficial layers of cells. It 

 develops independently of light, and its intensity depends merely 

 upon the degree of maturity or ripeness. Red, however, is a con- 

 stituent of the cell sap. It is capable of being influenced by a 

 number of agencies, and its intensity depends primarily upon the 

 amount of light received during the later stages of maturity. 



A test of the effect of light upon apples after they were picked 

 was made by the Pennsylvania Experiment Station. In this test 

 some 200 York Imperial apples were separated into four lots of 

 equal size, each lot containing approximately the same amount of 

 color at the beginning of the test. Two of these lots were arranged 

 to test the effect of sunlight and two the effect of electric light, 

 one of the lots in each case being darkened and all other factors 

 being kept essentially uniform. 



The results of the test, in brief, are that the lot exposed to sun- 

 light increased in redness by about 35 per cent, while in no other 

 case was any definite increase observable. In some instances an 

 apparent increase in the brightness, though not in the extent, of 

 the redness was observed, but this seemed to be due essentially 

 to the coming up of the yellow colors, thus increasing the contrast. 

 This test shows first the importance of sunlight, especially in con- 

 nection with maturity, and, second, that color is apparently inde- 

 pendent of anything contributed by the cell sap, at least after 

 normal size is reached. 



To obtain high color, however, it is desirable to maintain con- 

 nection with the tree as long as possible because of the unfavor- 

 able effects upon keeping quality that result from any considerable 

 exposure of the fruit after it is picked. 



