Oct. 29, 1921 Physiological Study of Grapefruit Ripening 269 



From an inspection of the curves it is evident that there is a decrease 

 in acidity as the season advances, the acid being highest in both cases at 

 the beginning of the season. The acid content is lowest at the fourth 

 pick and rises shghtly at the fifth pick. ColHnson ( j) shows a somewhat 

 similar decrease in acidity. This writer analyzed the fruit at more 

 frequent intervals but apparently did not begin sampling so early in 

 the season. According to his work there is a general tendency toward 

 lower acidity, though in a few of his series of analyses there is a higher 

 acidity toward the end of the season than in the midseason fruit. 



There is a rise in the percentage of total sugars during the season, the 

 total sugar content of pulp of the fifth pick being about double that of 

 the first pick. Collinson shows an increase in the total sugar content, 

 but it is not so marked, due probably to the fact that his series begins 

 later in the season. As showm in the curves (fig. i), the rise in total sugar 

 content during the first month is very sharp. The increase in percentage 

 of reducing sugar during the season is much more gradual and regular 

 than that of the total sugars. The percentage of this sugar in tlie pulp 

 a little more than doubles in the four months of the experiment. Much 

 the same ratio of increase is found in the total sugars. The cane sugar 

 curves are not so regular. There is, however, a marked increase in the 

 percentage of cane sugar. The mean of the two sucrose curves is always 

 higher than that of the reducing sugars except at the last sampling. 

 Collinson records a series of analyses in which the reducing sugar is 

 markedly higher than the sucrose during the latter part of the season. 

 The irregularities in the total sugar curves in the present work are due 

 to the variation in sucrose content. 



The percentage of dry matter, as determined in this work, is highest 

 at the first of the season between 11 and 11.5 per cent but drops in the 

 first month to between 9.5 and 10 per cent, the third and fourth analyses 

 giving about the same results. There seems to be, however, an increase 

 in the dry weights in the last month. 



A comparison of the percentage of peel (Tables I and II) at the time 

 the five different lots of fruit were placed in storage shows there is a de- 

 crease from 2)Z-Z to 21.2 and 45.6 to 18.2 per cent of peel by weight for 

 trees No. i and 2, respectively. The percentage of peel decreases much 

 more rapidly in the first month than in the succeeding month. In fact, 

 in the case of tree i there is only a slight decrease in the proportion of 

 peel to pulp in the last three pickings. At the time these last three 

 pickings were made, the fruit was ready for market. 



As might be expected, the decrease in thickness of the peel, as meas- 

 ured in these experiments, parallels the decrease in percentage of peel. 

 The peel was found to be 6.8 mm. and 8.1 mm. thick, respectively, for 

 trees i and 2 when the first pick was placed in storage, while it measured 

 4.5 mm. and 3.2 mm. at the first samphng of the fifth pick. This is a 

 reduction of 34 per cent and 60 per cent in the thickness of the skin fca: 



