10 POMOLOGY 



however, no marked difference between irrigated and non- 

 irrigated fruits in actual food or market value should be 

 charged to differences in composition." 



10. Chemical changes in the growing apple. ^ — Only data 

 for winter apples will be included here, since the same general 

 processes go on with smnmer varieties; the information, 

 however, is not so satisfactory owing to the uneven ripening 

 of the latter. 



This work was carried on with Ben Davis, Huntsman, and 

 Winter Paradise. The curves (Fig. 1) show in a striking 

 way the chemical changes which occurred throughout the 

 season, from June 16 until November 5. 



Using total sohds as a basis, it will be seen that starch 

 increases until the latter part of July when it has reached its 

 maximum, then it begins to decline constantly but does not 

 entirely disappear. The sucrose curve is almost the exact 

 reverse of the starch. This form of sugar starts with a low 

 percentage and continues low until the middle or latter part 

 of July, when, through the conversion of starch into sugar, it 

 begins to rise and continues until the fruit is ripe. On the 

 date of the first examination of these varieties, June 16, the 

 content of sucrose based on total solids was 4 per cent, and at 

 the last examination, on November 4, it amounted to 25.4 

 per cent of the total solid content of the apple, the rate of 

 increase being apparently no greater before the maximum 

 content of the starch than afterwards. Unlike the smnmer 

 apples which had been examined, the percentage of invert 

 sugar here increased from the date of the first examination to 

 approximately the date of the last, so that even in percentage 

 composition the amount of invert sugar did not reach its 

 maximum until the fruit was mature. 



In all three of the varieties of winter apples studied, the 



1 Data and comments are taken from work of Bigelow, W. D., H. C. 

 Gore, and B. J. Howard. U. S. Dept. Agr. Bur. Chem. Bull. 94. 1905. 



