

1917] OSTERHOUT—ADAPTA TION 149 



tion of water. In the process of dying the majority of cells exhibit 

 little or no increase in size, showing that they absorb little or no 

 water. Certain exceptional cells may swell and even burst, but 

 this is not the rule. 8 Moreover, the cells die in isotonic cane-sugar 

 solutions, although not as rapidly as in distilled water. 9 



We must look, therefore, for another explanation of these effects. 

 It has been pointed out by Loeb that when death occurs in distilled 

 water it must be due to diffusion from the protoplasm of substances 

 which are necessary to its normal activity, and that doubtless the 

 most important of these are inorganic salts. The reason why some 

 protoplasm is more tolerant of distilled water may be that it parts 

 less readily with certain salts which are combined (chemically or 

 mechanically) with it. 



It may also be true that the less tolerant protoplasm consists 

 more largely of substances (globulins or other colloids) which 

 undergo a change of state as soon as the concentration of salts 

 falls below a certain limit. In order that the cell should be intoler- 

 ant of distilled water the globulin (or other substance) need not 

 constitute a large part of the protoplasm, for it might, even in 

 small quantity, play an extremely important role, such as that 

 of a protective colloid or of a constituent of the plasma mem- 

 bers. These effects would be very simply explained by such an 

 assumption. 



Laboratory of Plant Physiology 



Harvard University 



8 In some cases failure to swell may be due to the rigidity of the cell wall, but 

 certain cells which have no rigid cell wall fail to swell under these conditions. 



9 This has been shown for certain animal cells by Loeb, Pfluger's Archiv 97:406. 

 1903. 



