XXXVIIL— RESPONSE OB' PLANTS TO WIRELESS 

 STIMULATION 



Sir J. C. Hose, 

 Assisted fnj 

 GURUPRASANNA DaS. 



A GROWING plant bends towards light, and this is, true 

 not only of the main stem but also of its branches and 

 attached leaves and leaflets. Light affects growth, the effect 

 being modified by the intensity of radiation. Strong stimu- 

 lus of light causes a diminution of the rate of growth, 

 but very feeble stimulus induces an acceleration. The 

 tropic effect is very strong in the ultra-violet region of the 

 spectrum with its extremely short wave length, 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 beyond 

 the infra-red region, we come across the vast range of 

 electric radiation, the wave lengths of which vary from 

 0-6 cm., the shortest wave I have been able to produce, 

 to others which may be miles in length. There thus arises 

 the very interesting question, whether plants perceive and 

 respond to the long ether 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 10"^ cm. ; but with 

 electric waves used in wireless signalling we have to deal 

 with waves 50 million times as long. The perceptive power 

 of our retina is confined within the very narrow range of 



