744 PLANT RESPONSE 



sive effect, its diminution by fatigue, and the induction of 

 tetanus under rapidly succeeding stimuli, in either case 

 corresponds to a like phenomenon in the other. Fatigue- 

 relaxations, moreover, under strong and long-continued 

 stimulation, are the same in both. And, turning to the 

 electrical mode of response, we find that the excitatory 

 condition of a tissue is indicated by its induced galvano- 

 metric negativity, whether the tissue be animal or vegetable ; 

 and further, similar physiological modifications, as induced 

 by the action of various external agents, are manifested by 

 similar changes in the two cases in the electrical response. 



As by the nerves of the animal, so also by certain con- 

 ducting channels in the plant-tissue, the state of excitation 

 is, in the two cases alike, transmitted to a distance ; and 

 this conduction takes place in both by propagation of proto- 

 plasmic changes. In both alike, cold reduces, and warmth 

 accelerates, the velocity of the transmission. In both alike, 

 the stronger the stimulus, the greater is the velocity with 

 which it is transmitted. In both, this velocity is diminished 

 with fatigue. Anaesthetics cause the temporary abolition 

 of conduction in both. The anode, again, blocks the trans- 

 mission of the excitatory wave in both. And, lastly, the 

 velocity of the transmission of excitation in the plant is com- 

 parable to that of its transmission in the nerves of some of 

 the lower animals. Thus, in a certain specimen of the sensi- 

 tive Mimosa, excitation was found to be transmitted with a 

 velocity of 14 mm. per second ; and in the ordinary plant 

 Ficus religiosa this velocity was determined at 9*4 mm. per 

 second ; while in the nerve of Anodon a value of 10 mm. 

 per second has been recorded. If, then, the characteristic 

 of nerve be to conduct excitation, it must be admitted 

 that the plant, like the animal, is provided with a nervous 

 system. 



In the matter of the excitation induced by the electrical 

 current, there is an equally remarkable similarity of effects in 

 animal and vegetable. Under normal conditions in both 

 cases, the kathode excites at make and the anode at break ; 



