494 CLIMBING AND INSECTIVOROUS PLANTS. [1862 



these experiments, together with the previously made remarks 

 on the functions of the parts, I cannot avoid the conclusion, 

 that Drosera possesses matter at least in some degree analo 

 gous in constitution and function to nervous matter. Now 

 do tell me what you think, as far as you can judge from my 

 abstract; of course many more experiments would have to be 

 tried ; but in former years I tried on the whole leaf, instead 

 of on separate glands, a number of innocuous* substances, 

 such as sugar, gum, starch, &c., and they produced no effect. 

 Your opinion will aid me in deciding some future year in 

 going on with this subject. I should not have thought it 

 worth attempting, but I had nothing on earth to do. 



My dear Hooker, Yours very sincerely, 



CH. DARWIN. 



P.S. We return home on Monday 28th. Thank Heaven ! 



[A long break now ensued in his work on insectivorous 

 plants, and it was not till 1872 that the subject seriously oc- 

 cupied him again. A passage in a letter to Dr. Asa Gray, 

 written in 1863 or 1864, shows, however, that the question 

 was not altogether absent from his mind in the interim : 



" Depend on it you are unjust on the merits of my beloved 

 Drosera ; it is a wonderful plant, or rather a most sagacious 

 animal. I will stick up for Drosera to the day of my death. 

 Heaven knows whether I shall ever publish my pile of experi- 

 ments on it." 



He notes in his diary that the last proof of the ' Expres- 

 sion of the Emotions' was finished on August 22, 1872, and 

 that he began to work on Drosera on the following day.] 



* This line of investigation made him wish for information on the ac- 

 tion of poisons on plants ; as in many other cases he applied to Professor 

 Oliver, and in reference to the result wrote to Hooker : " Pray thank Oli 

 ver heartily for his heap of references on poisons." 



