OSMOTIC PRESSURE IN RELATION TO PLANT DISTRIBUTION 179 



TABLE XLV. 

 OSMOTIC PRESSURE AND ITS ADJUSTMENT TO EXTERNAL MEDIUM. 



The figures recorded in the table show that normally 

 the alga has a slightly higher osmotic pressure than the 

 sea-water, and that this is practically entirely due to 

 electrolytes is demonstrated by the low value of M. When 

 kept in the dark for one day, there is scarcely any change 

 in the pressure, but the value of M appears to rise slightly. 

 Alteration of the medium, however, leads to a very rapid 

 readjustment of the pressure, through the diffusion out- 

 wards of the salts. As might be expected, the mean 

 molecular weight is practically unaffected by this change. 

 These experiments support those of Osterhout upon the 

 electrical resistance of Laminaria, from which he concluded 

 that the composition of the cell sap was almost identical 

 with that of the surrounding sa as regards its content 

 of electrolytes, and that the living protoplasm occasioned 

 the extra resistance which he found. The researches of 

 Osterhout have already been discussed in Chapter VII. 

 Since diluted sea-water is a physiologically balanced solu- 

 tion as regards its ionic composition, it is evident that the 

 injurious effects noticed on the large scale in Japan are 

 occasioned by fluctuations which are too rapid for the 

 proper adjustment to be effected. Accordingly, patho- 



