560 Proceedings of the 



some respects contradictory, were given by the different writers, 

 which it is, therefore, unnecessary to detail. The only certain results 

 appear to be the following-. In every stage of the progress of the 

 fruit towards maturity, carbonic acid is constantly produced. The 

 mode in which this acid is produced is explained in three different 

 ways by the different writers, all of which, however, are the result 

 rather of conjecture than of experiment. The progress of the fruit 

 towards maturity is thus described. First, the sap is converted into 

 a viscous liquid, (cambium,*) which circulates under the rind. 

 When this liquid becomes abundant, it allows part of its water to 

 escape, which evaporates and is converted into gum : it passes 

 through the peduncle to the ovary, where it forms the pericarpium. 

 In its course, it modifies itself by appropriating part of the oxygen 

 of the water of which it is composed, and thence result the various 

 acids, as citric acid, &c. As the fruit enlarges, the pellicle becoming 

 thin and transparent allows the light and heat to act with more 

 effect ; then commence the phenomena of ripening, properly so 

 called. The acids have a reaction on the cambium which circulates 

 in the fruit, and, by the aid of heat, transform it into a sweet or 

 syrupy substance. These acids soon disappear in their turn, being 

 subjected to a species of saturation by the gelatine. When these 

 phenomena are accomplished the maturity is perfect. Several of 

 the experiments made, in order to ascertain the mode in which the 

 saccharine matter is produced by the reaction of the acids on the 

 gum or gelatinous part of the fruit, are very curious, and merit par- 

 ticular attention. 



1. If the jelly of apples be acted on by a solution of a vegetable 

 acid in water, in a short time, (if a proper temperature be preserved,) 

 a saccharine matter, analogous to that of grapes, is obtained. 



2. The gum of peas, placed in the machine autoclavi *, with a 

 certain quantity of oxalic acid, and in a temperature of 257 F. 

 is converted into saccharine matter. 



3. Ordinary fecula, heated in the same manner, passes first into 

 a state resembling externally gum arable, but differing from it, inas- 

 much as when acted on by nitric acid it does not generate mucic acid. 



4. If this gum of fecula be added to the juice of unripe grapes, 

 and heated, the liquor becomes sweet. A similar effect is produced 

 if, after having saturated it with chalk and filtered it, tartaric acid 

 be dissolved in it and the solution boiled. We hence see why fruits 

 become sweeter by dressing, and grape-juice by evaporation, be- 

 cause part of the jelly is converted into saccharine matter. 



Circulation in Plants. An interesting conversation took place 

 in the Institute, on the 21st March, between MM. Cassini, Arago, 

 and Humboldt, on the subject of a letter written to the Academy by 

 M. Dutrochet, in which he attempted to prove that the supposed 

 circulation discovered by M. Schultz in the celandine (ficus elastica) 

 and other plants with milky juice, was a mere optical deception, 

 occasioned by a trepidation of the molecules, similar to that which 

 * An improvement of Papin's Digester, j 



