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Sir J. C. Bose and Mr. S. C. Guha. 



the perception of light. He rightly observes that "in zoological nomen- 

 clature, organs concerned with the perception of external stimuli have 

 always been known as sense organs, even among lower animals and in other 

 cases in which it is doubtful if the organs in question are responsible for 

 sensation in the psychological sense. It is, therefore, not only permissible, 

 but necessary in the interest of consistency to apply the term sense organ 

 to the analogous structure in plants." 



With regard to nerve and nervous impulse, I quote the following from 

 Bayliss (1), italicising the important passages : — 



" We find the presence of nerve at a very early stage of evolution. . . » 

 The effect of anything happening at one end of such a thread is conveyed 

 with great rapidity to the other end of the nerve, wherever it may be. Nerve 

 fibres have no other function than that of carrying excitation. When set into 

 activity by some influence, the disturbances set up disappear spontaneously 

 after a very short time if the stimulus ceases to act. . . . It is usual to 

 speak of a 'propagated disturbance ' passing along the nerve, or sometimes a 

 ' nervous impulse.' The most sensitive apparatus has been able to detect with 

 certainty one kind of change accompanying the passage of the propagated 

 disturbance, namely, an electrical effect." 



All the characteristics of nerve described above are also found in the con- 

 ducting tissues of plants. As regards the velocity of transmission of impulse, 

 it is not so high as in higher, but not so slow as in lower animals. Thus 

 in the frog's nerve the velocity is about 32 metres per second ; in Eledone it is, 

 however, as low as 1 mm. per second. The velocity in Mimosa is about 30 mm. 

 per second. Though the propagated disturbance causes no visible change, 

 yet the nervous impulse in plant, as in animal, may be detected by definite 

 electric change of galvanometric negativity ; the disturbance set up disappears; 

 spontaneously on the cessation of stimulus. If the electric contact be made 

 only at one point of the plant nerve, the other being at a distant indifferent 

 region, the electric response is monophasic. But if the contacts are made at 

 two points of the nerve, the proximal is the first to become galvanometrically 

 negative ; the propagated disturbance then reaches the distal point with con- 

 comitant negativity of that point. We thus obtain the characteristic diphasic 

 response of the nerve (see below). 



Since the nervous reactions in animals and plants are so essentially similar, 

 delay in full recognition of this fact will undoubtedly retard the advance of 

 science. I shall in the present paper demonstrate certain striking effects in 

 plants, which at first sight would no doubt appear as very astonishing, but 

 which in reality result from nervous reaction, usually regarded as the special 

 characteristic of the animal. I shall be able to show that in the plant a. 



