472 



LIFE MOVEMENTS IN PLANTS 



in the even series. In every case the upper side l)ecame 

 galvanonietriciill}^ positive. 



TABLE XXXVIII. — OEO-ELEC'l'RIC RESPONSE OK ROOT IN THE REGION 

 OE GROWTH. 



ADDITIVE ACTION-CURRENT AT THE TIP AND THE 

 GROWING REGION. 



It has been shown tliat under geotropic stimulus the 

 upper side of the tip, a, becomes galvaiiometrically nega- 

 tive, while the point A, higher up in the growing region, 

 becomes galvanometrically positive. If now we make the 

 two galvanometric connections with a and A, the induced 

 electric difference is increased, and the galvanometric res- 

 ponse becomes enhanced. 



Experiment 184. — The root was at first held viertical, 

 and two electric contacts made with a and A. In this 

 neutral position there is little or no current. But as soon 

 as the root was laid horizontal, an electro-motive response 

 was obtained which showed that, a was galvanometrically 

 negative, and A galvanometrically positive (Fig. 173d). 

 The induced electric response disappeared on restoration of 

 the root to the vertical position. I give below the results 

 of typical experiments with a vigorous specimen which 

 gave strong electric response. It was possible to repeat 



