5 12 Redfern . — On the Course of Absorption and the Position of 
tration on the intake of salts by plant cells, found that the relation 
between final internal concentration and final external concentration was 
i 
given by the adsorption equation y — kc m i where y — final internal concen- 
tration, c — final external concentration, and k and m are constants. 
They declined to put forward any proposals as to the mechanism of salt 
intake by the cell, on the ground that the data available were insufficient 
to justify any conclusions. 
It is a well-known fact that many substances, e. g. charcoal, form 
adsorption compounds with dyes and will decolorize a solution of dye with 
which they are in contact. 
The present investigation was undertaken in order to obtain quantita- 
tive data as to the course of absorption of dyes by plant tissue, and also to 
determine whether the results would furnish any evidence in favour of the 
adsorption theory of absorption put forward by Moore and Roaf. 
Methods. 
The method of experimentation employed was similar to that elabo- 
rated by Stiles and Jorgensen in their ‘ Studies in Permeability 5 ( 7 ). Storage 
tissue of various species was used ; in practice it was found that the best 
results were obtained with carrot tissue, and accordingly this tissue was 
employed in most of the experiments, though potato, artichoke, and turnip 
were also used. Cylinders of tissue were cut out by means of a cork-borer, 
2 cm. in diameter ; discs i mm. in thickness were cut with a hand micro- 
tome. The discs were thoroughly mixed and washed in two or three 
changes of distilled water ; they were then weighed in sets of two or four, 
and immersed in 50 c.c. of the experimental liquid, in corked bottles. The 
discs were weighed at intervals, in order that evidence might be obtained as 
to whether the tissue was in a healthy condition, or was injured by the dye. 
The concentration of the dye in the external solution was estimated colori- 
metrically ; each experiment was performed in duplicate. 
The observations were continued in each experiment until equilibrium 
was established, or until the colour of the dye in the external solution 
was so changed that a comparative estimation of the concentration was 
impossible. 
A number of water-soluble dyes were used, and in each case four 
concentrations were employed — o-i per cent., 0*05 per cent., o*oi per cent., 
0*005 per cent. 
In addition to experiments with living tissue, a few series of experi- 
ments were carried out with tissue which had been killed in a mixture of 
absolute alcohol and acetic acid before immersion in the experimental solu- 
tion. A few experiments were also made to determine the influence of 
temperature on the absorption of dyes. 
