302 Delf. — Studies of Protoplasmic Permeability by 
In experiments with dandelion scapes it was often noticed that after all 
plasmolytic contraction had ceased a gradual re-expansion of the tissues 
occurred, while the tissues were still surrounded with the same sugar 
solution. This naturally suggested a slow entry of the sugar molecules into 
the cells, causing an extension of the protoplast again. In order to test this 
hypothesis, the water-current was turned on again, and in the recovery 
of the tissues which ensued the extension was always slightly greater than 
the initial contraction had been. Since every care had been taken to ensure 
an initial turgidity of the tissues, the only explanation appears to be that 
there had been a penetration of the sugar molecules, which had therefore 
raised the osmotic pressure of the cells, and enabled them to take up more 
water at the same temperature than they could formerly have done. This 
point seems worth emphasizing, since sugar has always been regarded as the 
most impenetrable of substances with regard to the protoplast. 
The experiments at high temperatures are attended with the same 
difficulties as in the onion, and the curves obtained at temperatures above 
35° C. were corrected in the same way for the temperature effect. The 
collective curves for all the temperatures investigated are shown in Fig. 14, 
and the corresponding contractions and times are given in Table IV. It can 
