October 30, 1919] 



NATURE 



173 



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 con- 

 comitant increase of potential energy. Of the two 

 reactions, then, one is dynamic, attended by dissimila- 

 tory "down" change; the other is potential, asso- 

 ciated 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 reference to this I 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 movements, 

 to protoplasmic streaming and movements of the 

 chloroplastids, as well as the photonastic move- 

 ments 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 photosynthesis being relatively ineffective for 

 tropic reaction, and vice versa. 



Returning to the action of electric waves, since 

 they exert no photosynthetic action they might con- 

 ceivably induce the complementary tropic effect. 

 These considerations led me to the investigation of 

 the subject fourteen years ago, and my results 

 showed that very short electric waves induce a re- 

 tardation of rate of growth ; they also produce 

 responsive movements of the leaf of Mimosa when 

 the plant is in a highly sensitive condition.^ The 

 energy of the short electric waves is very feeble, and 

 undergoes great diminution at a distance; hence the 

 necessity for employment of a specimen of plant in a 

 highly sensitive condition. 



I resumed my investigations on the subject at the 

 beginning of this year. I wished to find out whether 

 plants in general perceived and responded to long 

 asther-waves reaching them from a distance. The 

 perception of the wireless stimulation was to be 

 tested, not merely bv the responsive movement of 

 sensitive plants, but also by diverse modes of response 

 given by all kinds of plants. 



The Wireless System. 

 For sending wireless signals I had to improvise 

 the following arrangement, more powerful means not 

 being available. The secondary terminals of a 

 moderate-sized Ruhmkorff's coil were connected with 

 two cylinders of brass, each 20 cm. in length ; the 

 sparking took place between two small spheres of 

 steel attached to the cylinders. One of the two 

 cylinders was earthed and the other connected with 

 the aerial 10 metres in height. The receiving aerial 

 was also 10 metres in height, and its lower terminal 

 led to the laboratory, and connected by means of a 

 thin wire with the experimental plant growing in a 

 pot ; this latter was put in electric connection with the 

 earth (Fig. i). The distance between the transmitting 

 and receiving aerial was about 200 metres, the maxi- 

 mum length permitted bv the grounds of the institute. 

 1 may state here that with the_ arrangement 

 described above I obtained very definite mechanical 

 and electric response to wireless impulse. For the 

 former I emploved the plant Mimosa ; the latter effect 

 ► was detected in all plants, sensitive and ordinary. 

 (Limitation of space will allo\y only a detailed 

 [description of the responsive modification of growth. 



1 PfcfTcr. "Phv«!oloev of Plants," vol. ii., p. 104. 



2 Bnse, " Plant Response." p. 618. (iqos-) 



■' A rlftailetl ace"unt of the response of plants to wireless stimulation will 

 ^he found in the Transactions of the Bose Institute, vol. i!., to be published 

 in November, 1919. 



NO. 2609, VOL. 104] 



Effect of Wireless Stimulation on Growth. 



For the detection of variation of growth it was 

 necessary to devise the extremely sensitive balanced 

 crescograph. In this apparatus a compensating 

 movement is given to the plant-holder by which the 

 plant subsides exactly at the same rate as its growth- 

 elongation, so that the tip of the plant remains at 

 the same point. This perfect balance is attained by 

 a variable regulator. The compound magnifying 



^ 



Fig. I, — Diagrammatic representation of the method of wireless stimulation. 

 On the right is seen the generating apparatus. The tip of the growing 

 plant is connected with the receiving aerial, and the lower part or the 

 flower-pot is earthed. 



lever attached to the plant records the movement of 

 growth. Under exact balance the record is hori- 

 zontal. .Any induced acceleration of growth would 

 upset the balance, with a resulting down record; 

 induced retardation, on the other hqnd, would cause 

 an upset in the opposite direction and an up curve. 

 The results given below show that growing plants 

 not only perceive, but also respond to the stimulus 

 of electric waves. These effects were found in all 



Fig- 2. — Automatic records obtained with the balanced crescograph showing 

 the effects of wireless stimulation on growth, (a) Feeble stimulus 

 inducing acceleration ; (^) strong stimulus inducing retardation of rate 

 of growth ; (c) series of growth responses by variation of growth due to 

 uniform moderate slimutation. Up-curve represents retardation of 

 growth and down-curve acceleration (seedling ot wheat). 



growing plants. The following records were obtained 

 with the seedlings of wheat. 



Effect of Feeble Stimulus. — Experiment i : I first 

 studied the effect of feeble stimulus. This was, 

 secured by decreasing the energy of sparks of the 

 radiator. The response was an acceleration of rate, 

 of growth as seen in Fig. 2, (a). This is analogous to 



