222 COMPARATIVE ELECTRO-PHYSIOLOGY 



ceased, the galvanometer-spot of light is thrown into a state 

 of oscillation, indicative of the local excitatory reactions at 

 the growing-point. 



These multiple pulsations of growth consist of alternating 

 positive and negative turgidity-variations. In dealing with 



the concomitant electrical response, however, we have seen 

 (p. 64) that the induced galvanometric negativity, owing to 

 its greater intensity, always overpowers the galvanometric 

 positivity, if the two occur in rapid succession. In growth- 

 pulsation, the constituent pulses are often extremely rapid. 

 Hence a growing-point may be expected to exhibit, galvano- 

 metrically, a resultant negativity. This consideration may 

 explain the observation of Johannes Miiller-Hetlingen, other- 

 wise unexplained, that the growing-points of both shoot and 

 root, in the seedling of Pisum sativum, are* negative, as 

 compared with the indifferent cotyledons. 



