1911.] PUBLIC DOCUMENT — No. 31. 185 



ficiilt, if not absolutely impossible. We can judge of their 

 presence and abundance only by the taste and the aroma of the 

 fruit. 



Return ing now to a consideration of the changes in the fruit 

 during the four periods of development already mentioned, wo 

 find them taking place somewhat as follows. During the period 

 of growth the amount of total solids of course increases greatly. 

 This increase may continue into the ripening period, but after 

 that there is a relative loss of total solids. The percentage, 

 also, of total solids increases during the period of growth and 

 during at least a part of the ripening period, but after that its 

 changes are much dependent upon conditions. The percentage 

 of acid in the fruit is largest in the early stages of growth, and 

 decreases more or less steadily during the entire history of the 

 fruit. The percentage of starch increases during the early part 

 of the growth, and at varying points, under different conditions, 

 it begins tu decrease, and disappears during the ripening ])roc- 

 ess. The sucrose increases pretty steadily until the period of 

 after rii)ening is complete, and then more or less rapidly de- 

 creases, and frequently entirely disappears in the process of 

 decay. The point of maximum of sucrose content may be taken 

 as the point of full maturity of the fruit, with a fair degree of 

 accuracy in most cases. The reducing sugars, dextrose and lovu- 

 lose, increase during the period of growth, and may or may not 

 increase slightly during ripening. In the later periods of ripen- 

 ing and decay they in most cases tend to increase, at least until 

 the final stages of decay. 



Comparatively little can be said regarding the behavior of 

 the insoluble solids during the periods of growth and ripening. 

 During the periods of after rij)ening and decay they pretty 

 steadily decrease. Probably fhey are at their maximum during 

 the early stages of ripening. The stage of development of the 

 insoluble solids of the apple is of great account in determining 

 the quality and condition of the fruit ; they compose for the 

 most part the cell walls of the fruit. During the later stages of 

 develojunent of the fruit the mi<ldle lamellae of the cell walls 

 seem to soften, perhaps through the action of some enzym. This 



