296 
Delf . — Studies of Protoplasmic Permeability. 
followed by a long period of constant length. In experiments with sugar, 
therefore, at these temperatures the solution was not applied until the 
initial expansion had ended. 
At temperatures above 30° C. the preliminary expansion is maintained 
for a time, but is soon followed by a considerable contraction, probably 
owing to an escape of cell-sap caused by the increased permeability for salts 
at high temperatures. This contraction appeared in about two hours in an 
experiment at 36° C. (Fig. 9, a), and since the plasmolytic shrinkage is 
completed within half an hour at that temperature, no correction for the 
temperature effect is needed. 
Fig. 9. Curves showing effect of temperature on onion in distilled water at 36° C. (a) and 
plasmolytic contraction at the same temperature, (b) with 0*18 grm. M. sugar. Ordinates are 
observed scale readings. 
The contraction at that temperature (Fig. 9, b) was followed by an 
expansion indicated at E, X (Fig. 9, B), which is almost certainly due to the 
continued entry of the sugar molecules into the cells, but the expansion was 
not followed to its conclusion. 
At temperatures above 36° C. there was a marked contraction appearing 
after half an hour or even less of exposure to the water-current (Fig. 10, A). 
It therefore seemed advisable to apply the solution as soon as the initial 
expansion had ended, to avoid any unnecessary temperature effect. The 
plasmolytic contraction was finished in ten minutes or less, and the 
temperature contraction was then again evident (Fig. 10, B, C, D). In 
all the curves at these high temperatures there appeared to be an antagonism 
between the tendency to expand with entry of sugar, and to contract as the 
effect of the prolonged high temperature. An analysis of these secondary 
