104 



COMPARATIVE ELECTRO-PHYSIOLOGY 



tenable. There are cases, again, in which a large portion of the 

 incident stimulus is held latent for a time, to find subsequent 

 manifestation externally. This I have been able to demon- 

 strate by the discovery of multiple response in plants. Thus 

 while a single moderate stimulus in such cases evokes a 

 single response, a single strong stimulus is found to give 

 repeated or multiple responses. This I have shown, not 



only in mechanical, but also 

 in electrical response, and the 

 latter subject will be taken 

 up in detail in a subsequent 

 chapter. 



And, lastly, it follows 

 from what has been said, 

 that incident stimulus need 

 not always cause depreciation 

 of the energy of the tissue, 

 but that, on the contrary, 

 it may actually raise it above 

 par. I shall now describe an 

 example in which incident 

 stimulus was seen to find 

 bifurcated expression. In 

 fig. 76 is given a photo- 

 graphic record of contractile 

 responses in the style of 

 Datura alba, in which growth 

 had previously been in a state 

 of standstill. The first five 



responses of this series are seen to be uniform. A portion 

 of the stimulus applied must, however, from the first 

 have been absorbed and held latent in the organ, thus 

 increasing that internal energy, or tonic condition, on 

 which growth depends. For at the sixth response we 

 find that growth recommences, and the stimulus now 

 finds bifurcated expression, in maintaining response and in 

 renewing growth, as seen in the trend downwards of the 



FIG. 76. Photographic Record of 

 Responses of Style of Datura alba 

 in which Growth had come to a 

 Temporary Stop . 



The up curve shows contraction. As 

 long as the base-line is horizontal, 

 growth is seen to be at standstill. 

 Renewal of growth at sixth re- 

 sponse, after which growth-elon- 

 gation is shown by the trend of 

 the base-line downwards. 



