THE EFFECT OF IONS OF NaCl AND CaCls UPON 

 THE ELECTRICAL CONDUCTIVITY OF 

 CERTAIN COLLOIDAL MIXTURES 



NEWTON BALDWIN GREEN 



University of Cincinnati, Cincinnati, Ohio 



PART I 



The experiments described in this paper were suggested by the 

 discovery of Professor Osterhout that the permeabiUty of plant 

 tissues to various ions could be determined by measuring the 

 resistance offered by the tissue to an electric current. A de- 

 scription of his methods first appeared in 1912^ and since that 

 time he has reported numerous additional determinations of the 

 effect of a variety of substances upon permeability. 



The method employed by him is now well known, but for the 

 sake of clearness it may be well to give a brief description of it. 

 He allowed an alternating high tension electric current to pass 

 longitudinally through a stack of discs cut from the fronds of a 

 species of Laminaria. Each disc was covered with a fihn of sea 

 water, which remained after the excess had been drained off, and 

 the stack of discs was held rigidly by a rack of glass and hard 

 rubber so that the two electrodes were pressed firmly against 

 either end. He found that a cylinder of tissue of this description 

 gave a resistance which was fairly constant and considerably 

 higher than the resistance offered by a cylinder of dead tissue or 

 a similar volume of sea water. He considered this resistance to 

 be an indication of the hindrance offered to the passage of the 

 sea water ions by the living protoplasm. This is undoubtedly 

 true since the ions must pass from one electrode through all the 

 discs of tissue to the other, and he demonstrated that the film 



1 Osterhout, W. J. V. The Permeability of Protoplasm to Ions and the Theory 

 of Antagonism. Science 35: 112. 1912. 



303 



THE PLANT WORLD, VOL. 21, NO. 12 

 DECEMBER, 1918 



