244 COMPARATIVE ELECTRO-PHYSIOLOGY 



animals. For an exact vegetal analogue to the electrical 

 plate of Torpedo, we may take certain leaves in which the 

 ventral, or anterior, surface is formed of a prominent network 

 of highly excitable nervous elements, while the upper consists 

 of an indifferent and relatively inexcitable mass of tissue. An 

 example of this may be found in the leaf of Pterospermum 

 suberifolium (Rox.) whose lower surface is characterised by 

 a remarkably perfect venation, while the upper or posterior 

 is dry and leathery. Thus the nerve passing into an elec- 

 trical plate of Torpedo corresponds with the petiole attached 

 to the leaf just described, since in the two cases alike, it is the 

 ventral surface which contains the highly excitable nervous 

 elements. 



In the exceptional Malepterurus, on the other hand, 

 it is, as we have seen, a modified gland, and not a modified 

 muscle, which forms the posterior surface of an individual 

 electrical element. Morphologically speaking, the vegetal 

 analogue is found in such organs as the carpellary leaf of 

 Dillenia indica, or the pitcher of Nepenthe^ both of which 

 are glandular on their upper or inner surfaces. In point 

 of structure, then, these leaf-organs are analogous to single 

 discs or elements of the electrical organs of Torpedo and 

 Malepterurus respectively. But we have still, in the course 

 of the present chapter, to inquire whether the electrical 

 reactions are equally correspondent that is to say, whether, 

 on stimulation, the excitatory current in the type of vege- 

 table organ represented by the leaf of Pterospermum is or 

 is not, from the lower or anterior surface to the upper 

 posterior, as in the electrical plate of Torpedo ; and, con- 

 versely, whether in the type represented by the carpel of 

 Dillenia or the pitcher of Nepenthe the excitatory current is 

 from the posterior to the anterior surfaces, corresponding 

 with the discharge in the electrical element of Malepterums, 

 from the posterior glandular to the anterior non-glandular 

 surface. 



While dealing with the theory of the action of electrical 

 organs, I shall be in a position to show that the characteristic 



