RESPONSE TO WIRELESS STIMULATION 421 



incident ether-wave induced an electric response in the 



pulvinus, the more excitable lower half exhibiting galva- 



nometric negativity. On the cessation of stimulus there 

 was a recovery (Fig. 155). 



It is not at all necessary to employ the sensitive 

 Mimosa for exhibition of electric response ; for this is 

 universally exhibited by all plants. The only condition 

 for electric response is that the points of electric contacts 

 should be made with two unequally excitable areas in 

 the plant. This may be secured by artificial means as 

 by causing ' injury ' to one point of contact.* It is 

 however much better to take advantage of the natural 

 difference of excitability of two dillerent areas in the 

 organ as in the pulvinus of Mimosa. This difference 

 of excitability is also found between the inner and outer 

 sides of a hollow tubular organ as in the peduncles of 

 various lilies. I was thus able to secure specimens 

 which were far more sensitive to the action of electric 

 waves than the pulvinus of Mimosa. 



EFFECT OP WIRELESS STIMULATION ON GROWTH. 



There now remains the very interesting question as to 

 whether the effect of long ether waves induce any variation 

 of growth. The results given below show that growing 

 plants not only perceive but respond to the stimulus of 

 electric waves. The effects to be presently described are 

 exhibited by all plants. 



I shall, however, content myself in describing a typical 

 experiment carried with the seedling of wheat. The speci- 

 men was mounted on the Balanced Crescograph, and the 

 growth exactly balanced. This gives a horizontal record ; 

 an acceleration of growth above the normal is. in the 



♦"Comparative Electro-Physiology" — p. li'.t. 



