Cuap. IX, SUMMARY OF THE CHAPTER. 223 
@ 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, colchiciue, curare, and diluted alcohol 
would bave produced some marked effect; whereas 
