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A STUDY OF THE PROBLEM OF WATER ABSORPTION. 35 
than the sap itself. Even in the sap solution concentrated to 
one-tenth of its original volume, the spores, though they be- 
came plasmolysed, absorbed so much of the coloring matter 
that they appeared quite yellow when observed under the 
microscope. They became a much deeper color than the 
solution that surrounded them. This is an interesting case 
of selective absorption, and one in which the substance ab- 
sorbed is a product of the cells that show the absorption. 
Moreover, the coloring matter becomes more concentrated in- 
side than outside of the cell. This, like other examples of the 
same phenomenon, cannot be explained as due to diffusion. 
Diffusion would tend to equalize the concentration of the 
coloring matter inside and outside of the cell. If a mass of 
Monilia cells are placed in a small amount of water and left 
for several hours, the water does not become colored. None 
of the coloring matter diffuses out of the cells. When, how- 
ever, the cells are placed in a solution of Monilia cell-sap they 
quickly take up the coloring matter and become a much 
deeper color than before. Thus it seems that the reddish 
yellow substance contained in Monilia cells that are grown in 
the light is capable of passing into, but not out of, these cells. 
A semi-permeable membrane does not help us to explain this 
observation. 
3. Absorption of Water by Egg-Albumen. 
If asmall amount of egg-albumen be placed in a paper bag 
and suspended in distilled water, the albumen will take up 
water and the bag will gain in weight. Much less weight is 
gained when such a bag is suspended in a strong solution of 
sodium or potassium chloride. A number of experiments 
have been performed for the purpose of determining the effect 
of different concentrations of sodium chloride on the absorp- 
tion of water by egg-albumen. In all of these experiments 
the egg-albumen was taken from fresh hen’s eggs, placed in 
small paper bags and immersed in the solution to be tested. 
After bag No. 1 had remained in a 2M sodium chloride 
solution for eighteen hours and had gained only 1.2 per cent 
of its original weight, as shown by the table below, it was re- 
