o 



152 STATE POMOLOGICAL SOCIETY. 



daring their gi'owlli aiul riiicuing, us follows (Lauehv. Vcrsuchsstafc, xvii., 245; 

 Jour. Chem. Soc, xxviii., 281) : 



AUSTRIAN. Riesling. 



1. June 27th ^ .- 1.37 per cent. 1.01 per cent. 



3. August IGth 1.33 " '•' 1.23 " 



3. August22d - 2. IS " " 1.81 " 



4. August 28th - 4.25 " " 2.39 '' 



5. September 1st 2.53 " " 2,58 '' 



«. September 12th 4.49 " " 2.89 "' 



7. September 17th. 5.33 " " 3.87 '' 



8. September 23d.. . 7.71 " " 7.70 " " 



9. October 10th... 9.90 '' " 8.64 '' 



10. November 10th 9.90 " " 8.21 " " 



Whether the .s«,(7ar of fruits is formed \^\Va\\\ them, or introduced tlirougli 

 the stem, and, if formed in tlie fruits, froni what substance formed, are ques- 

 tions which have been investigated but not wholly settled. It has been pretty 

 generally held that starch in the unripe fruits is converted into sugar iu the 

 ripe fruits ; the fruit acids inducing the change, as we know they have power to 

 do. ]5ut starch is not found in the unripe stage of all fruits, and in the cases 

 where found, its (juantity is sometimes too small to serve as the source of all 

 the sugar of the ripened fruit. In the investigation of Ililger, above quoted, 

 the immature fruit was at no time found by microscopic examination to contain 

 starch. It appeared in the fruit stalks in June ; after August it almost wholly 

 disappeared from the fruit stalks, and was found only in the wood of the vines. 

 Payen (Compt. llend., liii, 313), reported that he had demonstrated the pres- 

 ence of starch in unripe fruits and its conversion to sugar during ripening; but 

 did not ascertain how much of the sugar of fruits is formed in this way. 



It has been advanced that sugar is formed /royM malic and oilier acids, during 

 ripening, eitlier in the fruit or in the ])arts of the plant supplying juices to the 

 fruit. Six molecules of malic acid and six molecules of tartaric acid, with nine 

 molecules (eighteen atoms) of oxygen, would furnish the atoms for formation 

 of four molecules of glucose, twelve molecules of water, and twenty-four mole- 

 cules of carbonic anhydride. Mercadante (Gazetta Chimica Italiana, v. 125; 

 Jour. Cliem. Soc, xxviii [1875], 904) made a series of determinations of the 

 malic acid and sugar in plums, commencing May 20th. The quantities of both 

 acid and sugar increased in the fruit so long as it was green and emitting oxy- 

 gen in the daylight; the branches which bore the fruit containing acid and 

 pectous substances but no sugar. During the same time, the pcctous and gum- 

 my substances in the green fruit had decreased from 6 per cent of the pulp to 

 3 per cent of the pulp. The investigator believed the sugar of the green fruit 

 to have been chiefly formed, in the fruit, from the ])ectous and gummy sub- 

 stances, under contact of the acids. As soon as the fruit, losing green color, 

 began to emit carbonic acid in tlie daylight, the acid in it began steadily to 

 decrease as the sugar increased. The increase of sugar at expense of the acid 

 in the pulp of plums is shown as follows: 



Sugar. ]\Iai-ic acid. 



June 20th ...16.52 2.76 (p. c. in pulp) 



June 24tli 16.64 2.46 " " " 



June30th 16.78 2.16 "' " " 



July4th 17.05 1.57 " " '' 



July 12th 17.38 0.82 '' " •" 



