480 



E. J. LUND 



into consideration will be clear from such experiments as those 

 reported by Bayliss ('11) on certain colloidal salts when uniform 

 distribution in a solvent is prevented by means of a membrane 

 permeable to the anion, but impermeable to the cation. How- 

 ever, it seems that in most if not all such cases a P.D. exists 

 between the outside and inside of the membrane, so that in either 

 case we should have to account at least in part for the difference 

 in deflection b}^ an inherent P.D. in the stem. 



In order to make clear the peculiarities of the records given in 

 the tables, a sample series of tests upon an apical piece of the 

 main stem of a colony is given as follows: 



APICAL END OF STEM PLACED ON 



Left electrode — Deflec- 

 tion in millimeters on 

 left scale 



21.0 

 20.0 

 17.5 

 17.0 

 15.0 

 14.0 



Right electrode — Deflec- 

 tion in millimeters on 

 left scale 



22.5 



26.5 



24.0 



23.0 



22.5 



20.0 



DIFFERENCES BETWEEN 



SUCCESSIVE DEFLECTIONS 



IN MILLIMETERS 



-1.5 

 -6.5 

 -6.5 

 -6.0 

 -7.0 

 -6.0 



The numbers represent the magnitude of the galvanometer 

 deflections in millimeters on the scale. The direction of the 

 deflection was the same in all the tests given in this paper. 

 The arrows indicate the sequence of the tests; thus the first test 

 with apical end of the piece on the right electrode gave a deflec- 

 tion of 22.5 mm. The 'position of the piece on the electrodes 

 was then reversed. The deflection was now 21 mm. in the same 

 direction on the scale. Returning the piece to its first orienta- 

 tion gave 26.5 mm., and again placing the apical end on the left 

 electrode gave 20 mm. The tests were repeated in this way until 

 six pairs of readings were obtained in serial order. The duration 



current, sufficiently weak to be practically harmless when passed through the root 

 of a seedling from base to tip, produced marked injury when passed through the 

 root in the opposite direction. Recent experiments in this laboratory by Mr. 

 Emmett Rowles on the growth of roots through which an electric current was 

 passing seemed to indicate a difference in the effect on growth when the current 

 passed in opposite directions. 



