i862.] CLIMBING AND INSECTIVOROUS PLANTS. 493 



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

 discussion 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 leis- 

 ure. 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 mat- 

 ter 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 fluid from cell to cell, for I can see the rate of absorp- 

 tion, which though quick, is far slower, and in Dionaea the 

 transmission is instantaneous ; analogy from animals would 

 point to transmission through nervous matter. Reflecting on 

 the rapid power of absorption in the glands, the extreme 

 sensibility of the whole organ, and the conspicuous move- 

 ment caused by varied stimulants, I have tried a number of 



substances which are not caustic or corrosive, 



but most of which are known'to have a remarkable action on 

 the nervous matter of animals. You will see the results in 

 the enclosed paper. As the nervous matter of different ani- 

 mals are differently acted on by the same poisons, one would 

 not expect the same action on plants and animals ; only, if 

 plants have diffused nervous matter, some degree of analo- 

 gous action. And this is partially the case. Considering 



