THE VEGETABLE KINGDOM. 439 



system. According to him, this structure is represented by 

 the granulations interposed between the cells. But with 

 the most powerful microscope the eye cannot perceive any- 

 thing that can be identified with the nerves of animals. 



Although the existence of nerves in plants may still be 

 matter of doubt, it is none the less certain that the irrita- 

 bility shown by the sensitive plant seems to be under the 

 empire of organs analogous to nerves, as it is influenced by 

 the same agents and in the same manner as animals. Nar- 

 cotics weaken its sensibility as they weaken ours. If opium 

 be sprinkled upon the plant it ceases to feel irritants, and 

 no longer contracts ; it is paralyzed. And, as we have said, 

 an electric shock kills it. 



But a still more extraordinary phenomenon is that this 

 plant knows, like ourselves, how to accommodate itself to 

 circumstances. Desfontaines, having placed one in his car- 

 riage on a journey, saw it contract all its leaves so soon as 

 it felt the shaking of the wheels. Then, strange to say, 

 while the journey was still continued, the Mimosa, having 

 recovered from its fright, opened all its leaves little by little, 

 and kept them expanded so long as the movement lasted. 

 It had accustomed itself to the motion. But as soon as the 

 vehicle stopped the same peculiarity was repeated, and on 

 starting the plant contracted afresh, only to open again 

 when farther off. 1 



1 In the Proceedings of the Botanical Congress at London, in 1866, there is 

 an exhaustive paper by Professor Caspary, on movements induced in different 

 trees by cold. It seems to be made out that the seat of such movements is the 

 protoplasm, not the outer cell-wall. The contractile power of the protoplasm is 

 strongly marked in the Selaginella mutabilis, which, when exposed to a bright 

 light, becomes of a pale whitish milky color, but resumes its green tint when the 



