322 CLIMBING AND [l8/2. 



[A long break now ensued in his work on insectivorous 

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

 occupied 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 ' Expression 

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

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



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 Dionaea. 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 on other points in 



