Equilibi'ium in the Intake of Salts htj Plant Cells. 461 



The calculated absorption ratios show very clearly that the degree of 

 absorption depends to a large extent on the nature of the ions absorbed. 

 Calcium ions are apparently far less absorbed than those of potassium or 

 sodium. 



Experiments in which at the equilibrium point reached in the intake of 

 salts by living tissues of various kinds the absorption ratio is less than unity, 

 that is, the final internal concentration is smaller than the external, have 

 been previously recorded. From our results it appears that the failure to 

 observe absorption ratios greater than unity has been due to the fact that 

 the concentrations of the solutions used have been too high.* The results 

 of previous workers are discussed in the following section. 



Discussion of Previous Worl: The Absorption Ratios found hy Nathansohn 



and Meurer. 



In his earlier work, Nathansohu (6) showed by means of chemical analyses 

 of the external liquid and of the expressed sap that the marine alga Codium, 

 in solutions of sodium nitrate, does not take up the nitrate ion to the extent 

 required to produce equal concentrations inside and outside the tissue. The 

 solutions he used were, however, relatively strong, varying from 0"5 per cent, 

 to 5 per cent, that is in the region between N/20 and normal. "We may quote 

 a few of his results. 



Table VIII. — Absorption Eatios in the case of Codium immersed in Sodium 

 Mtrate. (Data from Nathansohn.) 



External concentration. 



Time. 



Absorption ratio. 



per cent. 



days. 





0-5 



4 



0-56 



0-5 



10 



0-68 



0-5 



2 



OoS 



1-0 



5 



0-44 



1 -0 



5 



-49 



3-8 



2 



0-43 



4-8 



2 



0-41 



Nathansohn remarked, however, that in sea-water, where the concentration 

 of nitrate is iow, the nitrate ion is often found heaped up inside the tissue, 

 so that its concentration is greater inside than outside. 



* Nevertheless, it has often been observed that the concentration of a substance or ion 

 inside the cell could be greater than its concentration in the bathing iluid. See e.g., 

 Moore and Eoaf(4, 5)and Bayliss (1) for animal cells, Wodehouse (15) for plant cells 

 ( Vulnnia). 



