GEORGE T. SCOTT AND HUGH R. HAYWOOD 



41 



production of which is prevented by this inhibitor, 4) low temperatures. In 

 addition, experiments were carried out in which the effect of external sodium 

 concentration on potassium reaccumulation was studied. 



An examination of a large body of data indicates a close correlation between 

 potassium content and calculated cell water in Ulra, while sodium content is 



50 



45 



40 



35V 



25 



20 



POTASSIUM 



20 



40 



80 



100 



120 



60 



-hours- 

 Fig. I. Influence of illumination and darkness on the potassium content of Ulva lactuca. 



most consistent on a dry weight basis. For these reasons the potassium and 

 sodium are expressed as indicated although essentially the same results appear 

 when the data for each ion are expressed on either basis. 



The variation in ion contents in these experiments cannot be a reflection of 

 changing cell volume, since although the percentage dry weight varied between 

 the limits of 25 and ^;^ there was no trend correlating with any variation in ion 

 contents. 



Influence of Light and Dark. In these experiments two groups of algae were 

 used, the one being maintained in the light throughout the experiment and the 



