Permeability 241 
the same weight and surface. The experiments at any one tem¬ 
perature were all conducted in triplicate or quadruplicate, so that 
for a comparison of the rate of water intake at four different tem¬ 
peratures, 12 or 16 sets of 20 disks were required, 3 or 4 at each 
temperature. The probable error of the determinations was calculated 
so that some idea of the degree of reliability of the results might be 
obtained. The temperatures were maintained constant by means 
of thermostat baths provided with gas-mercury-toluene regulators. 
Time in hours 
Fig. 7. Curves illustrating the influence of temperature on the absorption 
of water by potato tuber. (After Stiles and Jorgensen.) 
The course of water absorption at different temperatures by 
potato and carrot is shown in Figs. 7 and 8. From these absorption¬ 
time curves the rate of swelling of the tissue has been determined in 
the same way as the rate of shrinkage in Miss Delf’s experiments, 
that is, by measuring the tangent of the angle made with the time 
axis by the tangent to the curve at any particular stage of swelling. 
By comparing the rate of intake of water at different temperatures 
at the same stage of swelling, the following temperature coefficients 
for the rate of intake of water are obtained. 
