EASILY CONVERTIBLE INTO SUGAR. 69 



sugar by very different means. This change occurs in 

 the process of germination, as in malting, and it is easily 

 accomplished by the action of acids. The metamor- 

 phosis of starch into sugar depends simply, as is proved 

 by analysis, on the addition of the elements of water. (12) 

 All the carbon of the starch is found in the sugar ; none 

 of its elements- have been separated, and, except the 

 elements of water, no foreign element has been added 

 to it in this transformation. 



In many, especially in pulpy fruits, which when un- 

 ripe are sour and rough to the taste, but when ripe are 

 sweet, as, for example, in apples and pears, the sugar 

 is produced from the starch which the unripe fruit 

 contains. 



If we rub unripe apples or pears on a grater to a 

 pulp, and wash this with cold water on a fine sieve, the 

 turbid liquid, which passes through, deposits a very fine 

 flour of starch, of which not even a trace can be de- 

 tected in the ripe fruit. Many varieties become sweet 

 while yet on the tree ; these are the summer or early 

 apples and pears. Others, again, become sweet only 

 after having been kept for a certain period after gather- 

 ing. The after-ripening, as this change is called, is a 

 purely chemical process, entirely independent of the 

 vitality of the plant. When vegetation ceases, the fruit 

 is capable of reproducing the species, that is, the ker- 

 nel, stone, or true seed is fully ripe, but the fleshy cov- 

 ering from this period is subjected to the action of the 

 atmosphere. Like all substances in a state of erema- 



