i872.] CLIMBING AND INSECTIVOROUS PLANTS. 495 



C. Darwin to Asa Gray. 



[Sevenoaks], October 22 [1872]. 



... I have worked pretty hard for four or five weeks on 

 Drosera, and then broke down ; so that we took a house near 

 Sevenoaks for three weeks (where I now am) to get complete 

 rest. I have very little power of working now, and must put 

 off the rest of the work on Drosera till next spring, as my 

 plants are dying. It is an endless subject, and I must cut it 

 short, and for this reason shall not do much on Dionasa. 

 The point which has interested me most is tracing the nerves ! 

 which follow the vascular bundles. By a prick with a sharp 

 lancet at a certain point, I can paralyse one-half the leaf, so 

 that a stimulus to the other half causes no movement. It is 

 just like dividing the spinal marrow of a frog : — no stimulus 

 can be sent from the brain or anterior part of the spine to the 

 hind legs ; but if these latter are stimulated, they move by 

 reflex action, I find my old results about the astonishing 

 sensitiveness of the nervous system (! ?) of Drosera to various 

 stimulants fully confirmed and extended. . . . 



[His work on digestion in Drosera and other points in 

 the physiology of the plant soon led him into regions where 

 his knowledge was defective, and here the advice and assistance 

 which he received from Dr. Burdon Sanderson was of much 

 value :] 



C. Darwin to J. Burdon Sanderson. 



Down, July 25, 1873. 



My dear Dr. Sanderson, — I should like to tell you a little 

 about my recent work with Drosera, to show that I have 

 profited by your suggestions, and to ask a question or two. 



I. It is really beautiful how quickly and well Drosera and 

 Dionasa dissolve little cubes of albumen and gelatine. I kept 

 the same sized cubes on wet moss for comparison. When 

 you were here I forgot that I had tried gelatine, but albumen 

 is far better for watching its dissolution and absorption. 

 Frankland has told me how to test in a rough way for pep- 



