1863.] CLIMBING AND INSECTIVOROUS PLANTS. 485 



eluding the growing tip) is constantly and slowly twisting round 

 making a circle in from one-half to two hours ; it will some- 

 times go round two or three times, and then at the same rate 

 untwists and twists in opposite directions. It generally rests 

 half an hour before it retrogrades. The stem does not become 

 permanently twisted. The stem beneath the twisting portion 

 does not move in the least, though not tied. The movement 

 goes on all day and all early night. It has no relation to light 

 for the plant stands in my window and twists from the light 

 just as quickly as towards it. This may be a common 

 phenomenon for what I know, but it confounded me quite, 

 when I began to observe the irritability of the tendrils. I do 

 not say it is the final cause, but the result is pretty, for the 

 plant every one and a half or two hours sweeps a circle (ac- 

 cording to the length of the bending shoot and the length of 

 the tendril) of from one foot to twenty inches in diameter, 

 and immediately that the tendril touches any object its sensi- 

 tiveness causes it immediately to seize it ; a clever gardener, 

 my neighbour, who saw the plant on my table last night, said : 

 " I believe, Sir, the tendrils can see, for wherever I put a 

 plant it finds out any stick near enough." I believe the 

 above is the explanation, viz. that it sweeps slowly round and 

 round. The tendrils have some sense, for they do not grasp 



each other when young. 



Yours affectionately, 



C. Darwin. 



C, Darwin to J. D. Hooker, 



Down, July 14 [1863]. 



My dear Hooker, — I am getting very much amused by 

 my tendrils, it is just the sort of niggling work which suits 

 me, and takes up no time and rather rests me whilst writing. 

 So will you just think whether you know any plant, which 

 you could give or lend me, or I could buy, with tendrils, re- 

 markable in any way for development, for odd or peculiar 

 structure, or even for an odd place in natural arrangement. I 

 have seen or can see Cucurbitaceae, Passion-flower, Virginian- 



