GEORGE T. SCOTT AND HUGH K. HAYWOOD 



57 



composition with respect to these cations. If the experiment is carried beyond 

 75 hours in the presence of phenyl urethane the inlluence of the inhibitor is not 



POTASSIUM 



2 20 



20 30 

 - HOURS- 



SODIUM 



20 30 



-HOURS- 



FiGS. 15 {top) and 16. Loss of potassium and gain of sodium in Ulva resulting from o.ooi 

 m/1. phenyl urethane. At the arrow 3 samples were transferred to running sea water. 



reversible on restoration to light and running sea water (fig. 17). As in Ulva 

 an active process must be postulated for cation regulation. The possibility of 

 passive accumulation of potassium in the sap does not exist, since, as pointed 

 out by Osterhout, the concentration of dififusible anion in the sap is not low 



