300 Delf. — Studies of Protoplasmic Permeability by 
The tangents of these curves at any stage in the contraction gives 
a measure of the rate of the contraction at that stage, and these values found 
for different curves at the same stage and plotted to the corresponding 
temperatures as abscissae give the relative rate of plasmolysis. The values 
of these tangents for the onion are given in Table III. 
Table III. 
Rate of plasmolysis at 30 %, 50 %, and 70 % contraction, in onion, irrigated with 0*18 grm. M. 
sugar. 
Temperature . 
Amount of contraction completed. 
30 %• 50 %• 7 ° %• 
5° C. 
2*8 
2*3 
o *77 
i 4 ° C. 
3*4 
2*0 
i*4 
1 9 0 C. 
4-5 
3*4 
2 *3 
26° C. 
6*2 
5 -o 
2*7 
30° C. 
14*3 
10*0 
f * o 
33 ° C. 
26*6 
I 2*9 
8*5 
3 /°C. 
25*4 
19*5 
1 8*3 
3 ^° C. 
23 
18*4 
ii*9 
42 0 C. 
51-8 
36*2 
12*1 
From this table it can be seen that at all stages of the plasmolytic 
shrinkage produced by these subtonic solutions, there is a considerable 
increase of the rate of shrinkage with rise of temperature. The temperature 
effect seems to be much more marked towards the end of the contraction, 
but as the endings of experiments were always more liable to possible 
errors of interpretation than any other part it seems better to take the 
values at mid-plasmolysis, and these are plotted to the corresponding 
temperatures in Fig. 12, The coefficients of increase of permeability 
deduced from the curve are : 
Temperature 
range . 
5°-i5° 
1 0 °— 20 ° 
i 5 s - 2 5 0 
20°-3O° 
25°-3r 9 
3 0 °- 4 0 ° 
Coefficient of increase 
for io° C. 
i-4 
i’5 
2*0 
2*6 
2?9 
3*o 
B. Scape of Dandelion . 
In order to confirm these results, similar experiments were carried out 
with the scapes of dandelions, which have a more homogeneous structure 
than onion leaves. The solution employed was 0*3 grm. M., and was found 
by trial as for the onion. It was afterwards found that the dilute solutions 
used for each plant bore the same ratio to the corresponding isotonic 
solution (1 : 1*4), which is in itself a somewhat striking testimony to the 
trustworthiness of the apparently arbitrary method of selection of these 
subtonic solutions. 
