Permeability 89 
results were obtained by Miss Redfern (1922 b) with dyes. This does 
not mean, of course, that the rate of equilibration is more rapid in 
the case of stronger solutions, for a greater quantity of salt is absorbed. 
The influence of concentration on the absorption of aniline dyes 
was examined by Sziics (1910). His method is not ideal. Filaments 
of Spirogyra were placed in solutions of methyl violet of different 
concentrations varying from 0-000125 to 0-00125 per cent, and the 
time determined that had to elapse for the cells to acquire a standard 
depth of tint. It was found that the product of time and concen¬ 
tration was a constant over this range of concentrations, from which 
Fig. 14. Absorption of potassium chloride by carrot root tissue immersed in 
solutions of various concentrations. (From the data of Stiles and Kidd.) 
it was concluded that Fick’s law holds for the absorption of the dye. 
It will be remembered that Fick’s law states that 
dQ = - DA dt, 
where dQ is the quantity of substance diffusing through a cross- 
section of area A in the time dt , D being the coefficient of diffusion and 
