Of THE FRriT. 



783 



gum, and matters of a like nature. According to M. Buignet's 

 investigations, the cause of the change of the primarily formed 

 cane sugar into fructose is not the acids of the fruits, but ap- 

 pears to depend on the influence of a nitrogenous body playing 

 the part of a glucosic ferment, analogous to that which M. Eer- 

 thelot has extracted from yeast. M. Buignet adds, that " the 

 abundance in which starch is found distributed through the 

 vegetable kingdom, leads to the supposition that it is the true 

 source of the saccharine matter in fruits. Its presence cannot, 

 however, be detected in green fruits, either by the microscope or 

 by iodine, excepting in green bananas, which contain a notable 

 quantity of starch." M. Buignet also notices that green fruits 

 contain a particular astringent principle resembling tannin, 

 which is capable of being converted into a sugar identical with the 

 sugar from starch, under the influence of dilute acids and a 

 proper temperature. The proportion of this tannin diminishes 

 in fruits in the same ratio that the proportion of sugar increases. 

 The changes which take place in the composition of fruits 

 during ripening are well exhibited in the following table founded 

 upon Berard's observations : — 



The pericarp of some fruits has developed in it during the 

 process of ripening fixed and essential oils, as well as other 

 substances of an aromatic nature. According to Fremy, the 

 inner walls of the cells of succulent fruits in an unripe state, 

 consist of a substance called pcctose, which is insoluble in water. 

 This body has not been isolated, but is converted in ripe fruits 

 into pectine, which is soluble in water. Pectine is afterwards 

 transformed first into pcctosic and then into 2^<^ctic acid. Fremy 

 has also noticed, that at the period of maturation the thickness of 

 the cell-walls diminishes rapidly ; hence, it would appear that 

 these transformations of the pectic compounds play an important 



