THE CHEMISTRY OF FRUIT-RIPENING. 463 



often termed grape-sugar. It is the same compound that is largely 

 manufactured from starch, and called starch-sugar. It is much less 

 sweet than cane-sugar, and less abundantly soluble in water, having 

 an oily or " mealy " taste. As made from starch, it is now much used 

 in certain candies. When in the uncrystallizable form, glucose (Icevu- 

 lose) is the same as " fruit-sugar," the uncrystallizable product ob- 

 tained to some extent in manufacturing cane-sugar, and which forms 

 a part of the sirups of the market. Many of the fruits contain cane- 

 sugar (which is the same as beet-sugar and maple-sugar), and certain 

 rare varieties of sugar are found in some fruits. 



Buignet decided that the apple, peach, plum, raspberry, orange, 

 and pineapple, contain cane-sugar, with glucose (mostly as Icevidose). 

 The sugar of the grape, cherry, gooseberry, and fig, consists wholly 

 of glucose. 



The average proportion of sugars in ripe fruits is given, by Frese- 

 nius, as follows (the smallest percentages being placed first) : 



Peaches, 1.6 per cent, (not varying very widely). 



Apricots, 1.8 per cent, (from 1.1 to 2.7). 



Plums, round red, 2.1 per cent, (from 2.0 to 3.5). 



Greengages, 3.1 per cent. 



Raspberries, 4.0 per cent, (from 3.0 to 5.0). 



Blackberries, 4.4 per cent. 



Strawberries, 5.7 per cent, (from 3.2 to 7.0). 



Currants, 6.1 per cent, (from 4.8 to 6.6). 



Gooseberries, 7.1 per cent, (from 6.0 to 8.2). 



Pears, red, 7.4 per cent. 



Apples, 8.4 per cent, (from 5.9 to 10.4). 



Cherries, 9.8 per cent, (from 8.5 to 13.1). 



[Summer peaches, 11.6 per cent. Berard's analysis.] 



Grapes, 14.9 per cent, (from 13 to 19). 



It is seen from this list that the sweetness of fruit has but slight 

 correspondence with its proportion of sugar. Currants were found 

 to have more sugar than raspberries, blackberries, or strawberries, 

 and over three times as much as the peaches examined by Fresenius. 

 All analysts agree in the predominance of grapes for their quantity 

 of sugar. The sweetness of fruit is probably favored less by large 

 proportions of sugar than by three other conditions, namely : 1. Small 

 proportions of acids; 2. Large proportions of pectous substances; 3. 

 Presence of cane-sugar instead of grape-sugar. 



The sugar of fruits is chiefly formed or deposited in them during 

 their ripening. Berard found that the pulp of cherries, unripe, con- 

 tained only 1.1 per cent, of sugar; ripe, 18.1 per cent.; gooseberries, 

 unripe, 0.5 per cent. ; ripe, 6.02 per cent. In 1862 Hilger determined 

 the sugar of grapes, at ten periods during their growth and ripening, 

 as follows {Landw. Versicchsstat, xvii., 245 ; Journal of the Chemical 

 Society, xxviii., 281) : 



