310 Delf. — Shi dies of Protoplasmic Permeability. I. 
on PP- 3 °°) 3 ° 3 , and the most acceptable series for the two plants 
(the 50 per cent, series) are plotted against temperature in Figs. 12 and 1 5. 
As the force at work was, by selection, equal in all these cases, 
the differences of rate shown are true measures of the state of the per- 
meability. It is evident that the augmenting effect of temperature increases 
to the highest temperature investigated. 
These curves are in opposition to the generally accepted curve for this 
relation put forward by F. van Rysselberghe in 1901 (see Fig. 16, p. 306), 
which indicates hardly any rise of permeability after 20° C. In Section VII 
van Rysselberghe’s data are critically examined, and it is pointed out that 
his method of deriving a temperature-relation from his data (plasmolysis of 
cylinders of pith in 25 per cent. (0-731 grin. M.) cane-sugar) cannot give 
a true relation. 
The data themselves are also open to some criticism on account of the 
very strong plasmolysing solution used. Here the effective force at work is 
so great that the shrinkage is very quick even at medium temperatures, and 
there seem to be mechanical limitations to any quicker shrinkage at high 
temperatures even though the protoplasm becomes more permeable. 
Further consideration will be devoted to the theoretical significance of 
the experimental results now brought forward in a later paper of this 
series. It will suffice at present to give the quantitative conclusions 
as follows : 
1. The permeability of protoplasm for water, as measured by the rate 
of tissue-shrinkage in a dilute sugar solution, is increased continuously 
by temperature up to the highest temperature investigated — 42 0 C. 
2. Taking the value of the permeability at 25 0 as unity, the following 
relative values are established : 
Temperature 
5° 
10° 
15 
20° 
2 5° 
cu 
0 
0 
35° 
4°° 
Onion 
0-36 
0-44 
0-50 
o*66 
1*0 
i*7 
2-9 
5*° 
Dandelion 
— 
0*2 2 
0-30 
°'5° 
1*0 
i-9 
3*° 
5*o 
3. An approximate measure of this increase is given by the following 
sets of temperature-coefficients for increase of permeability with rise 
Temperature. 
Onion 
Dandelion 
m O _ .O 
leaf. 
scape. 
5 - J 5 
i-4 
— 
I0°-20° 
1-5 
2*3 
T 5°- 2 r° 
2*0 
3*3 
20°-30° 
2*6 
3-8 
25°-35 c 
2-9 
3*° 
30°-40° 
3*0 
2-6 
