THE PERMEABILITY OF PROTOPLASM 105 



sea-water. They were attached to the cover -glasses which 

 formed the roof of an irrigation chamber. After definite 

 root-hairs had been sketched by the aid of a camera lucida 

 during irrigation with sea-water, the latter was changed 

 for distilled water. This had been carefully prepared by 

 using glass vessels only, and plugs of absorbent cotton as 

 stoppers. It was not toxic to sensitive species of Spirogyra 

 or root-hairs of Gypsophila, whereas water distilled from 

 metal stills is poisonous to such cells. 



Within half an hour of the application of distilled water, 

 the Zostera cells were plasmolyzed, so as to remain in 

 contact with the walls at the lower side only. This slow- 

 ness of action is not, however, a characteristic of false 

 plasmolysis, for the colourless terminal hairs of Polysi- 

 phonia violacea contract rapidly, a marked reaction being 

 visible at the ends of the cells within two minutes from 

 their immersion in distilled water. Additional proof that 

 this was not due to any toxic action of the distilled water 

 was furnished by the fact that pond, river, or spring water 

 could be substituted for distilled with the same result. 



The phenomenon may in part be accounted for by an 

 increased permeability of the cell surfaces, as the result 

 of which the substances which maintain the osmotic 

 pressure diffuse out. That the effects are not due to an 

 absorption of water is shown by the failure of the cells 

 to increase in size, as well as by the action of isotonic 

 solutions of cane-sugar, which produce the same altera- 

 tions as distilled water, though not so rapidly. 



The increase in permeability appears to be occasioned 

 by the loss of substances upon which the maintenance of 

 normal conditions depends. Of these, the inorganic salts 

 are the most important, for in sea-water to which an equal 

 volume of distilled water has been added the cells remain 

 turgid, whereas when three volumes of fresh water are 



