POMACES 375 



in the ripening process. The content of sucrose (cane sugar) 

 increases steadily in the ripening process up to a maximum 

 and then suddenly decreases. There is a rapid decrease of 

 starch throughout the entire period. Invert sugar (a mix- 

 ture of glucose and fructose) increases throughout the ripen- 

 ing period while the total sugar increases up to the date when 

 starch entirely disappears, after which time it fluctuates 

 slightly. Malic acid, which gives the fruit its sourness, 

 gradually becomes less and less. Ripening takes place in 

 two stages. The first stage involves that portion of the fruit 

 within the core line (Fig. 158). Here there is at first a de- 

 crease in the starch content just between the locules, at the 

 tips of the carpels. This loss extends outward from these 

 points to the core line. The second stage of the ripeningproc- 

 ess involves the region outside the core line. At first, 

 streaks free of starch appear in the midst of this area. Soon 

 the middle portion of the area becomes free of starch. There 

 is a gradual increase of this starch-free area, the last regions 

 to ripen being V-shaped areas radiating from the vascular 

 bundles as seen in cross-section. Furthermore, anatomical 

 changes take place in ripening. The middle lamellae of the 

 cells soften, resulting in a slight separation of the cells, an 

 increase in the regularity of the cell outline, in the size of 

 intercellular spaces, and amount of intercellular air. 



"Mealiness." — This results from a softening of the middle 

 lamellae; those varieties that are comparatively very mealy 

 have correspondingly weak lamellae. When a cell divides 

 into two, the common primary wall between them becomes 

 the middle lamella of the thicker wall formed by the deposi- 

 tion of material from both protoplasts. Hence in the mature 

 cell wall, the primary or first-formed wall appears as a defi- 

 nite layer between the added layers. Separation of two ad- 

 jacent cells naturally takes place along this middle line. 



