REVIEW OF RESPONSE OF ANISOTROPIC ORGANS 711 



of indifferent tissue on the posterior surface. Hence the 

 current of response is from the more excitable anterior to 

 the less excitable posterior. In the second type the pitcher 

 of Nepenthe and the electrical plates of Malepterurus the 

 posterior surface being glandular and therefore exceptionally 

 excitable, the responsive current is from posterior to anterior. 



In taking rheotomic observations on the response to 

 electrical stimulation in various anisotropic leaves virtually 

 acting, as has been shown, like electrical plates it was found 

 that in sluggish specimens the maximum electro-motive value 

 was attained '2 second after the exciting shock. This was 

 also the value of the period which elapsed after the applica- 

 tion of moderate mechanical stimulation. With vigorous 

 specimens, however, such as the leaves of Nymphcea alba, 

 the maximum effect was attained in a much shorter time, 

 that is to say, in about -03 second. In the electrical organ 

 of Torpedo the corresponding period has been found to be 

 oi second. The response of electrical organs is found to be 

 repeated or multiple. In the rheotomic records obtained 

 with leaves, further, the multiple apices of the curve show 

 that the response of vegetable organs also has this multiple 

 character Multiple response, however, is not the peculiar 

 characteristic of the electrical organ, but has been shown to 

 take place in various kinds of animal and vegetable tissues. 



Again, that this peculiarity of definitely uni-directioned 

 response, whether the excitation be homodromous or hetero- 

 dromous is not distinctive of life, with its specific powers 

 of assimilation and dissimilation, but of anisotropy in 

 general, with its consequent differential excitability, was 

 shown by the fact that similar uni-directioned responses to 

 homo- or hetero-dromous shocks were given by an inorganic 

 structure, consisting of prepared lead (fig. 167). 



We have next to pass in review the question of the 

 response of plant and animal tissue to stimulus of light 

 The various motile responses, induced by light in plants, are 

 so diverse and so apparently incapable of being explained 

 by any single reaction of fundamental excitation, that it 



