182 DROSERA ROTUNDIPOLIA. [Chap. IX. 



and thoir glands to pour forth an increased amount of modi- 

 fied 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 trans- 

 mission. This led me to try the several alkaloids and other 

 substances which are known to exert a powerful influence on 

 the nervous system of animals. I was at first encouraged in 

 my trials by finding that strychnine, digitaline, and nicotine, 

 which all act on the nervous system, were poisonous to Dro- 

 sera, and caused a certain amount of inflection. Hydrocy- 

 anic 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 extremely poisonous 

 to Drosera, and quickly cause strong inflection, it seems prob- 

 able that strychnine, nicotine, digitaline, and hydrocyanic 

 acid, excite inflection by acting on elements in no way an- 

 alogous 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, atropine, veratrine, 

 colchicine, curare, and diluted alcohol would have produced 

 some marked effect ; whereas these substances are not poison- 

 ous and have no power, or only a very slight one, of in- 

 ducing inflection. It should, however, be observed that cu- 

 rare, colchicine, and veratrine are muscle-poisons that is, 

 act on nerves having some special relation with the muscles, 

 and, therefore, could not be expected to act on Drosera, The 

 poison of the cobra is most deadly to animals, by paralysing 

 their nerve-centres,' yet is not in the least so to Drosera, 

 though quickly causing strong inflection. 



Notwithstanding the foregoing facts, which show how 

 widely different is the effect of certain substances on the 

 health or life of animals and of Drosera, yet there exists a 

 certain degree of parallelism in the action of certain other 

 substances. We have seen that this holds good in a striking 

 manner with the salts of sodium and potassium. Again, 

 various metallic salts and acids, namely those of silver, mer- 

 cury, gold, tin, arsenic, chromium, copper, and platina, most 

 or all of which are highly poisonous to animals, are equally 

 8o to Drosera. But it is a singular fact that the chloride of 



* Dr. Payrer. ' The Tbanatopbldia of India,' 1872, p. 4. 



