7l6 PLANT RESPONSE 



same statement holds good in the case of the plant. The 

 passage of mere hydro-mechanical disturbance could not 

 have been affected in any way by the anode. 



Nor is this transmission of excitation confined to sensi- 

 tive plants alone. The fact that it occurs in all plants alike 

 I have been able to demonstrate by various other methods, 

 in using which we are rendered independent of the mo- 

 tile indications afforded by lateral leaflets. Thus by the 

 Electrotactile Method we are enabled to detect, in any 

 zone of the plant, the moment of arrival of the state of 

 excitation from a distant point (p. 259). The Electro- 

 motive Method, again, displays the moment of arrival of the 

 wave by the induced galvanometric negativity of the point 

 (p. 261). The Chemical Method, again, shows the arrival 

 of the wave of excitation by the projection of a dense 

 precipitate, produced in a suitable solution (p. 255). All 

 these different methods give us results which are in mutual 

 agreement. 



As showing how ill founded is the common distinction as 

 between sensitive and ordinary plants, it was demonstrated 

 that the velocity of transmission in some of the latter is 

 greater than in the former. Thus in Ficiis rcligiosa the 

 velocity was determined at 9*4 mm. per second, whereas in 

 the 'sensitive' Neptttnia oUracca it was only ri mm. per 

 second. The velocity of transmission of the excitatory 

 impulse in plants is found, again, to be of the same order 

 of magnitude as in the nerves of lower animals (p. 252). 



I have shown further that excitation is transmitted in 

 the plant in both directions. It is, however, interesting to 

 note that, generally speaking, the facility of this trans- 

 mission is greater centrifugally — that is to say, in the 

 direction of the ascent of sap— than centripetally. Thus, for 

 example, in a petiole of BiopJiytuniy while the centripetal 

 velocity was i'8 mm. per second, the centrifugal velocity was 

 3 27 mm. per second. 



Since conduction of stimulus takes place by transmission 

 of protoplasmic change, such change is naturally conducted 



