ARTICLES 



65 



concentration of this substance in each was equal. He there- 

 fore concluded that the permeability of the plasmatic mem- 

 branes of the cells may change according to the concentration 

 of certain substances inside and outside the cell. 



Graves l found that the root-hairs of Ruppia maritima when 

 placed in slightly concentrated sea- water (1 10 per cent.) at first 

 showed no reaction, but eventually they became plasmolysed. 

 He also ascertained the rapidity of this reaction exhibited by 

 the cells of the leaves when treated with solutions of sodium 

 chloride of different strengths. It will be observed that the 

 results of Graves are of a nature opposite to those obtained 

 by Janse for Chcetomorpha. 



The Erquy work on root-hairs 2 was carried out on seed- 

 lings because it was found to be practically impossible to 

 remove successfully the earth from the roots of mature plants 

 without damaging the region of the active root-hairs. 



The osmotic pressure of the root-hairs of Salicornia and 

 Suceda was first investigated ; this was found to vary some- 

 what according to the place in which the seedlings were grow- 

 ing, and in all cases it was considerably higher than that of an 

 ordinary mesophytic seedling. 



Table II sets forth the results : 



Table II 



A number of seedlings were then placed for some time in 

 solutions of sodium chloride in serial decreasing concentra- 

 tions. On testing the root-hairs, it was found to be very diffi- 

 cult to determine exactly their osmotic strength. Fresh seed- 

 lings were therefore selected and were mounted in a molecular 

 solution of sodium chloride (5-85 per cent.) ; all those whose 

 root-hairs showed no plasmolysis, and whose osmotic equiva- 



1 Graves, Trans. Connecticut Acad. Arts and Set. 14, 1908. 



2 Hill, New Phyt. 7, 133, 1908. 



