Stiles and Jergensen . — Studies in Permeability . F. 423 
increased temperature and the subsequent shrinkage at higher tempera- 
tures. It would appear that even after half an hour the shrinkage at 40° C. 
has already commenced. In Fig. 5, where these results are shown graphi- 
cally, the first part of the curve of swelling at this temperature is assumed. 
From the values, obtained from fifteen to twenty hours, in both the 
cases of carrot and potato, it seems reasonable to conclude that temperature 
exerts no marked influence on the equilibrium value of maximum swelling, 
apart from the secondary action at higher temperatures to which reference 
has already been made. 1 
The rate of swelling at any particular moment is given by the tangent 
of the angle made with the time axis by the tangent drawn to the curve at 
that particular point. 
In order to measure the effect of temperature on swelling it is necessary 
to compare the rates of swelling at the same 
stage of swelling at the different temperatures. 
The numbers given in Table VI are obtained 
in this way. The table shows the comparative 
rates of swelling at different temperatures when 
the tissue has increased 10 per cent, in weight, 
i. e. when it has swollen to about half the maxi- 
mum possible swelling. 
It does not follow, however, that carrot and 
potato are in the same absolute stage of swelling, 
as we cannot conclude that the initial conditions 
of the two tissues are the same in regard to water- 
content and turgor pressure. Nevertheless, although the comparison of the 
temperature coefficients of potato and carrot obtained here must be made 
with a certain amount of reservation, yet the recorded differences are striking 
and indicate considerable differences in constitution of the two tissues. 
Fig. 5. Curves illustrating 
the influence of temperature 
on the swelling of carrot in 
distilled water. 
Table VI. 
Rate of Swelling of Potato and Carrot 
at Different Temperatures . 
Temperature. Potato. 
io° C. 0*15 
20 0 C. 0*45 
30°C. i*2 
Carrot. 
i-3 
i-7 
2*5 
These numbers give the following values for the temperature coefficient 
of swelling : 
Table VII. 
Temperature Coefficients of Swelling of Potato and Carrot . 
Temperature. Potato . Carrot. 
io°— 20° C. 3*0 1 e 3 
2o°-3o°C. 2*7 i*6 
1 Cf. Pfeffer ( 14 ), p. 138 : ‘ Since by a rise of temperature of I5°C. the (osmotic) pressure is only 
raised from 100 to 105*5, it is evident that temperature can never exercise any marked direct effect 
turgor in plants.’ 
