520 Redfern . — On the Course of Absorption and the Position of 
TABLE VI ( continued ). 
Temperature . 
Original external con - 
centration in per cent . 
External concentration in 
24 krs . 48 hrs . 
per cent , after - 
72 hrs . 
20° C. 
0-1 
0.07 
0-07 
— 
0.05 
0-03 
0-02 
— 
O-OI 
0-004 
0.002 
— 
0-005 
0.0015 
0-0015 
— 
o° C. 
0.1 
0-07 
O.06 
°-°55 
0.05 
0-02 
0.015 
0.015 
0.01 
0.005 
0-003 
0.0015 
0.005 
0.0025 
0-002 
0.001 
Discussion. 
j. Course of absorption. 
The absorption curves obtained in this investigation are similar to 
those obtained by Stiles and Kidd (6) for the intake of salts from solution 
by plant tissue — that is, the curves rise steeply at first, but gradually become 
more horizontal as the condition of equilibrium is approached. 
The curves also show that the condition of equilibrium is reached 
much more rapidly with more concentrated external solutions than is the 
case with more dilute external solutions. This might be expected as the 
effect of the dye is much more harmful in concentrated solutions than in 
dilute solutions, as is shown by the rapid loss of weight by the discs in the 
case of the former. This loss of weight indicates loss of turgor. 
2 . Influence of the acidity or basicity of the dye employed. 
The majority of the dyes used in this investigation are basic ; only two 
acid dyes were employed, viz. Congo red and eosin. The first of these 
was not absorbed in appreciable quantity by the plant tissue from solutions 
of any concentration, and the external solutions became darker in colour, 
presumably owing to reactions taking place between the dye and substances 
which diffuse out from the cells. In the case of eosin, the dye was not 
appreciably absorbed from the more concentrated solutions, and only to 
a slight extent from the more dilute solutions. 
The basic dyes, on the contrary, with one exception (aniline blue), 
were rapidly absorbed, and when equilibrium was reached the internal 
concentration was frequently greater than the external concentration, 
especially in the case of the more dilute solutions. 
These results are in accord with the earlier ones of Ruhland (5), who 
found that basic dyes were rapidly absorbed, while acidic dyes were, at most, 
absorbed to a very slight extent. The results also agree with those of 
Collander (1) in his recent work on the sulphonic acid dyes. He found 
that these dyes were absorbed in relatively slight amounts by plant tissue. 
In an extensive series of experiments, he estimated the ratio between the 
