CHAP. IX SUMMARY OF THE CHAPTER. 223 



a fresh leaf from another plant. The latter had most of its 

 tentacles strongly inflected within 30 m. ; whereas the leaf which 

 had been exposed to the carbonic acid remained for 24 hrs. in 

 the solution without undergoing any inflection, with the excep- 

 tion of two tentacles. This leaf had been almost completely 

 paralysed, and was not able to recover its sensibility whilst still 

 in the solution, which from having been made with distilled 

 water probably contained little oxygen. 



Concluding Remarks on the Effects of the foregoing 

 Agents. As the glands, when excited, transmit some 

 influence to the surrounding tentacles, causing them 

 to bend and their glands to pour forth an increased 

 amount of modified secretion, I was anxious to 

 ascertain whether the leaves included any element 

 having the nature of nerve-tissue, which, though 

 not continuous, served as the channel of transmission. 

 This led me to try the several alkaloids and other 

 substances which are known to exert a powerful in- 

 fluence on the nervous system of animals. I was at 

 first encouraged in my trials by finding that strych- 

 nine, digitaline, and nicotine, which all act on the 

 nervous system, were poisonous to Drosera, and caused 

 a certain amount of inflection. Hydrocyanic acid, 

 again, which is so deadly a poison to animals, caused 

 rapid movement of the tentacles. But as several in- 

 nocuous acids, though much diluted, such as benzoic, 

 acetic, &c., as well as some essential oils, are ex- 

 tremely poisonous to Drosera, and quickly cause 

 strong inflection, it seems probable that strychnine, 

 nicotine, digitaline, and hydrocyanic acid, excite in- 

 flection by acting on elements in no way analogous 

 to the nerve-cells of animals. If elements of this 

 latter nature had been present in the leaves, it might 

 have been expected that morphia, hyoscyamus, atro- 

 pine, veratrine, colchicine, curare, and diluted alcohol 

 would have produced some marked effect; whereas 



