SOCIETY OF CENTRAL ILLINOIS. 315 



marked. Before the end of July the fruit had fallen off, when the 

 canes and leaves were collected and analyzed. A few of the figures 

 of tlie result will sutiice: 



Under Under 



Uncovered. White Cloth. Black Cloih. 



Per Cent. Per Cent. Per Cent. 



Glucose 1.2G 0.8G6 0.00 



Tartaric Acid 0.90 0.660 0.1:365 



Pure Ash 1.54 1.28 0.82 



These few of the results obtained are sufficiently marked to need 

 no explanation. We notice a gradual decrease of all important and 

 desirable constituents in the different vines, in relation to the extent 

 to which they are deprived of light. If the quantity of canes and 

 leaves produced by the uncovered vine be placed at 100, then the 

 weight formed under the white cloth should be placed at 80, and 

 that under the l)lack cloth at 10. If, now, we apply the percentages 

 just given, we have the following: 



White Black 



Uncovered. Cloth. (.'loth. 



Glucose (sujjar) 126.01 6.29 0.00 



Tartaric Acid 00. 15 53.52 1 .86 



Pure Ash 154.12 102. 5:J 8.22 



This shows the influence of the interference of the supply of 

 light to the entire vine; that the amount of sugar produced ui.der 

 the action of diffused light is much less than that produced in direct 

 sunlight, and that, when maintained in darkness, the production of 

 sugar is insignificant, or even nil. And Levy has shown by a series 

 of elaborate and carefully-conducted experiments, that the fruit itself 

 developes better and is of better quality when exposed to the light 

 than when maintained in darkness, all other conditions being the 

 same. To determine this important fact he chose upon the same 

 vine and the same cane, bunches of grapes of as nearly as possible the 

 same size, the same apjiearance and the same vigor. One of them he 

 allowed to remain under all the conditions of exposure to air and 

 sunlight, while the other he enclosed within a case so constructed 

 that the flow of supplies of nutriment from the vine should be in no 

 way impeded, and the ImuicIi could enjoy all the advantages of fresji 

 air and atmospheric moisture of the bunch not so confined, with the 

 single exception that all possible access of light to it was cut off. 

 And when the fruit was thus fully developed, and had attained per- 

 fect maturity, both were analyzed in the same way. The fruit de- 

 veloped in darkness contained much less of sugar and more of acid 

 than the fruit produced under more favored circumstances, and from 

 all the results of his experiments, which were so often repeated as to 

 leave no doubt of the accuracy of the data they furnish, he natur- 

 ally concluded that the larger the quantity of light the fruit has 

 during its development, the better will be its quality both for table 

 consumption and for wine. 



