RESPONSE TO WIRELESS STIMULATION 177 



growth. The tropic effect is very strong in the ultra-violet 

 region of the spectrum with its extremely short wave-length 

 of light ; but the effect declines practically to zero as we move 

 towards the less refrangible rays, the yellow and the red, with 

 their comparatively long wave-length. As we proceed further 

 in the infra-red region we come across the vast range of electric 

 radiation, the wave-lengths of which vary from the shortest 

 wave I have been able to produce (0-6 cm.) to others which may 

 be miles in length. There thus arises the very interesting question 

 whether plants perceive and respond to the long aether-waves, 

 including those employed in signalling through space. 



At first sight this would appear to be very unlikely, for the 

 most effective rays are in the ultra-violet region with wave- 

 length as short as 20 x io~ 6 cm. ; but with electric waves used 

 in wireless signalling we have to deal with waves 50,000,000 

 times as long. The perceptive power of our retina is confined 

 within the very narrow range of a single octave, the wave- 

 lengths of which lie between 70 x io~ 6 cm. and 35 x io~ 6 cm. 

 It is difficult to imagine that plants could perceive radiations so 

 widely separated from each other as the visible light and the 

 invisible electric waves. 



But the subject assumes a different aspect when we take into 

 consideration the total effect of radiation on the plant. Light 

 induces two different effects which may broadly be distinguished 

 as external and internal. The former is visible as movement ; 

 the latter finds no outward manifestation, but consists of an ' up ' 

 or assimilatory chemical change with concomitant increase of 

 potential energy. Of the two reactions, then, one is dynamic, 

 attended by dissimilatory ' down ' change ; the other is potential, 

 associated with the opposite ' up ' change. In reality, the two 

 effects take place simultaneously ; but one of them becomes 

 predominant under definite conditions. 



The modifying condition is the quality of light. With refer- 

 ence to this 1 quote the following from Pfeffer : ' So far as is at 

 present known, the action of different rays of the spectrum gives 

 similar curves in regard to heliotropic and phototactic move- 

 ments, to protoplasmic streaming and movements of the chloro- 

 plastids, as well as the photonastic movements produced by 

 growth or by changes of turgor. On the other hand, it is the 

 less refrangible rays which are most active in photosynthesis.' 

 The dynamic and potential manifestations are thus seen to 

 be complementary to each other, the rays which induce 



