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PHYSIOLOGY OF NUTRITION 



The isosmotic coefficients were determined in the following manner. Three 

 cane sugar solutions, 0.20-, 0.22- and 0.24- volume-molecular, and three solu- 

 tions of potassium nitrate, 0.12-, 0.13- and 0.14- volume-molecular, were em- 

 ployed, for plasmolytic experiments with epidermal cells of Curcuma 

 rubricaulis. Each experiment lasted seven hours. The results obtained 

 in three such tests are given in the following table, where n denotes that 

 no plasmolysis occurred, hp denotes that about half of the cell* were 

 plasmolyzed and p denotes that most of the cells were plasmolyzed. IC 

 denotes the isosmotic concentration, taken to be osmotically equal to the cell 

 sap. Volume-molecular concentration is denoted by m. 



Since the osmotic pressure produced by a volume-molecular potassium 

 nitrate solution is taken as 3, the numbers in the„last column are to be multi- 

 plied by 3, and the average ratio thus becomes t^i, which is the isosmotic 

 coefficient of saccharose when that of potassium nitrate is considered as 3. 



A list of substances thus tested by deVries is given in the next table, together 

 with their isosmotic coefficients, as actually derived from experiment and also 

 in round numbers. The next to the last column gives the percentage concen- 

 trations thus found to be isosmotic with a one-tenth volume-molecular solution 

 of KNO3, and the last column gives the osmotic pressure produced by a i-per 

 cent, solution of each substance. 



