128 STUDIES IN ELECTRO-PHYSIOLOGY: 



many other examples could be found, but the foregoing 

 should be in themselves sufficient to establish the point I 

 have been endeavouring to make. 



Unfortunately it is not always possible to find parallel 

 illustrations, but I may take the opportunity afforded by 

 this chapter to give the views of some authorities upon 

 points of resemblance between animal and vegetable 

 organisms. In Vegetable Physiology, by J. R. Green, 

 F.R.S., I find the following : " If we turn to the reaction 

 of the leaf of the Dion&a to contact, we find that the whole 

 leaf may be somewhat roughly handled without closing, 

 so long as no contact is made with the hairs, three in 

 number, which arise on a particular portion of the blade. 

 So soon, however, as one of these is touched, the leaf closes. 



" It is impossible to avoid the conclusion that we have 

 to do in these instances, which are only representative 

 ones, with a localisation of sensitiveness, or the differentia- 

 tion of sense-organs. . . . The power of sight is very 

 complete in the higher animals . . . but in the lower 

 animals it becomes less and less perfect, till in some it goes 

 probably little further than the power of appreciating light. 

 This power we have seen to be possessed by certain parts 

 of the young seedlings of various plants in a very high 

 degree, and by other organs to a less extent. The sense of 

 touch may be compared with the power of responding to 

 the stimulus of contact shown by tendrils and by the tips 

 of roots ; the muscular sense, or power of appreciating 

 weight, is perhaps comparable to the property of respond- 

 ing to the attraction of gravitation, while the chemotactic 

 behaviour of certain organisms suggests a rudimentary 

 power of taste or smell, or both. ... If we turn to a 

 second feature of the nervous system, we find that the 

 motor mechanism of the plant seems at first to be entirely 

 different from that of the animal. Closer consideration, 

 however, lessens the difference considerably. The motor 



