320 CLIMBING AND [1862. 



me a week, for, at the present moment, I care more about 

 Drosera than the origin of all the species in the world. But 

 I will not publish on Drosera till next year, for I am frightened 

 and astounded at my results. I declare it is a certain fact, 

 that one organ is so sensitive to touch, that a weight seventy- 

 eight-times less than that, viz., y^qq of a grain, which will 

 move the best chemical balance, suffices to cause a conspicu- 

 ous movement. Is it not curious that a plant should be 

 far more sensitive to the touch than any nerve in the human 

 body ? Yet I am perfectly sure that this is true. When I 

 am on my hobby-horse, I never can resist telling my friends 

 how well my hobby goes, so you must forgive the rider." 



The work was continued, as a holiday task, at Bourne- 

 mouth, where he stayed during the autumn of 1862. The dis- 

 cussion in the following letter on " nervous matter " in Drosera 

 is of interest in relation to recent researches on the continuity 

 of protoplasm from cell to cell :] 



C. Darwin to J. D. Hooker. 



Cliff Cottage, Bournemouth. 

 September 26 [1862]. 



MY DEAR HOOKER, — Do not read this till you have leisure. 

 If that blessed moment ever comes, I should be very glad to 

 have your opinion on the subject of this letter. I am led to 

 the opinion that Drosera must have diffused matter in organic 

 connection, closely analogous to the nervous matter of animals. 

 When the glands of one of the papillae or tentacles, in its 

 natural position is supplied with nitrogenised fluid and 

 certain other stimulants, or when loaded with an extremely 

 slight weight, or when struck several times with a needle, the 

 pedicel bends near its base in under one minute. These 

 varied stimulants are conveyed down the pedicel by some 

 means ; it cannot be vibration, for drops of fluid put on quite 

 quietly cause the movement ; it cannot be absorption of the 



