Walter Stiles 
238 
polation. The relative values for the rate of linear shrinkage of the 
tissue at the stage of half-contraction are shown in Table XXVII, 
the values for 25 0 C. being taken as unity. 
Table XXVII 
Relative rates of linear contraction of onion leaves and dandelion 
scapes in subtonic solutions of sucrose at different temperatures. 
(Data from Miss Delf) 
Relative rate of linear contraction 
Temperature 
,- 
-i 
in centigrade 
Onion leaves 
Dandelion scapes 
degrees 
in o-18 M sucrose 
in 0-3 M sucrose 
5 
0-36 
— 
10 
°'44 
0-22 
15 
0-50 
0-30 
20 
o-66 
0-50 
25 
I'O 
I'O 
30 
i -7 
1-9 
35 
2-9 
3-o 
40 
5 -o 
5-o 
From these numbers the temperature coefficients (< 2 10 , see Chapter 
III, p. 101) for a rise of io° C. were calculated, with the results given 
in Table XXVIII. 
Table XXVIII 
Temperature coefficients for rate of linear shrinkage of onion 
leaves and dandelion scapes in subtonic sucrose solutions. 
(Data from Miss Delf) 
Range of Temperature coefficient (Q 10 ) 
temperature in , - K -^ 
centigrade degrees Onion leaves Dandelion scapes 
5-i5 i-4 — 
10-20 i*5 2-3 
15-25 2-0 3-3 
20-30 2-6 3-8 
25-35 2-9 3-0 
30-40 3-0 2*6 
It is particularly interesting to consider how far these temperature 
effects are to be regarded as effects of temperature on permeability 
of the protoplasm, as they are assumed to be by Miss Delf. 
If the permeability of the cell or tissue to water is defined as the 
quantity of water passing through unit area of the cell mem¬ 
branes (cell wall + protoplasm) in unit time under unit difference 
of pressure we have the equation 
dw 
dt 
Z{P e -P+T)A, 
