522 Redfern . — Absorption of Dyes , &c. 
6. Influence of the concentration of the external solution. 
The results given above show that the percentage absorption of the dye 
is increased as the external solution becomes more dilute. This is very 
clearly shown in the case of the basic dyes, which were absorbed from all 
concentrations ; in the case of the acid dyes and aniline blue, if there was 
any appreciable absorption it only took place in the more dilute solutions. 
When the logarithm of the final external concentration is plotted 
against the logarithm of the final internal concentration the resulting graph 
approximates to a straight line, in the case of most of the basic dyes and 
eosin. This indicates that the relation between these concentrations corre- 
JL 
sponds to the adsorption equation y — kc m i where y — final internal concen- 
tration, c — final external concentration, and k and m are constants. 
Although this fact cannot be taken as proof that the absorption of dyes by 
plant tissue is a process of adsorption, yet it may be regarded as evidence 
in favour of the view that adsorption plays an important part in the 
absorption process ; the results obtained in the few experiments carried out 
at different temperatures support this view. In several cases, however, 
notably with tissue other than carrot, the process seems to be complicated 
by some other reaction, possibly one of chemical combination. 
Literature cited. 
1. Collander, R. : Uber die Permeabilitat pflanzlicher Protoplasten fur Sulfosaurefarbstoffe. 
Jahrb. fur wiss. Bot., lx. 354-410, 1921. 
2. Moore, B., and Roaf, H. E. : Direct Measurement of the Osmotic Pressure of certain Colloids. 
Biochem. Journ., ii 34-73, 1907. 
3. , Roaf, H. E., and Webster, T. A. : Direct Measurement of the Osmotic Pressure 
of Casein in Alkaline Solution. Biochem. Journ., vi. 110-26, 1912. 
4. Pfeffer, W. : Uber Aufnahme von Anilinfarben in die lebende Zelle. Unters. a. d. Bot. Inst. z. 
Tubingen, ii. 179-332, 188 6. 
5. Ruhland, W. : Die Bedeutung der Kolloidalnatur wassriger Farbstoffe fur ihr Eindringen in 
die lebende Zelle. Ber. der deut. bot. Ges., xxvi a. 772-82, 1908. 
6. Stiles, W., and Kidd, F. : The Influence of the External Concentration on the Position of the 
Equilibrium attained in the Intake of Salts by Plant Cells. Proc. Roy. Soc., B., xc. 448- 
70, 1919. 
, and Jorgensen, I. : Studies in Permeability, I. Ann. Bot., xxix. 349-67, 1915. 
7 . 
