108 RELATION OF PLANTS TO ELECTRICITY 



which roots of Phaseolus seedlings turn toward the cathode is 1.2 

 at a temperature of 20 C. If the strength of the current is in- 

 creased beyond this, mechanical effects due to the disturbance of 

 the conditions of turgidity are produced which may cause a cur- 

 vature in the opposite direction. Such curvatures are not to be 

 ascribed to electrotropism. The maximum currents for Helian- 

 thus are 1.3 8, and Lepidium, 3.5 d. 



Sporophores of Phycomyces exposed to the action of Hertzian 

 waves curved away from the source of the rays much after the 

 manner of apophototropic curvatures. ' 



167. Electrotaxis. The movement of the entire body of an 

 organism in such manner as to constitute locomotion, in response 

 to currents passing through the medium in which it is found, has 



a 



Fig. 50. Cell with walls of rubber and clay for testing electrotaxis of motile or- 

 ganisms. The electrodes are seen to be applied to the clay walls, and the organisms 

 are aggregated near the kathode. After Verworn. 



been observed only in animals, but the method of investigation is 

 given here with the idea that repeated tests with motile zoo- 

 spores and other free moving plants may secure some positive re- 

 sults. The following method will show the electrotactic move- 

 ments of paramoecium in a very striking manner. 



1 Hegler, R. Ueber die physiologische Wirkung der Hertz'chen Electricitatszellen 

 auf Pflanzen. 1892. 



Loeb, J. Ueber die physiologische Wirkung elektrischen Wellen. Arch. Ges. 

 Physiol. 69 : 99. 1897. 



Brunchorst, J. Die Funktion der Spitze bei den Richtungsbewegungen der 

 Wurzeln. Galvanotropismus. Ber. d. Deut. Bot. Ges. 2 : 204. 1884. 



