X OBITUARY 290 



carried home some plants, and on giving them 

 some insects saw the movements of the tentacles, 

 and this made me think it possible that the insects 

 were caught for some special purpose. Fortu- 

 nately, a crucial test occurred to me, that of placing 

 a large number of leaves in various nitrogenous 

 and non-nitrogenous fluids of equal density ; and 

 as soon as I found that the former alone excited 

 energetic movements, it was obvious that here was 

 a fine new field for investigation." (I, p. 95.) 



The researches thus initiated led to the proof 

 that plants are capable of secreting a digestive 

 fluid like that of animals, and of profiting by the 

 result of digestion ; whereby the peculiar appara- 

 tuses of the insectivorous plants were brought 

 within the scope of natural selection. Moreover, 

 these inquiries widely enlarged our knowledge of 

 the manner in which stimuli are transmitted in 

 plants, and opened up a prospect of drawing closer 

 the analogies between the motor processes of plants 

 and those of animals. 



So with respect to the books on " Climbing 

 Plants" (1875), and on the " Power of Movement 

 in Plants " (1880), Darwin says ; 



" I was led to take up this subject by reading a 

 short paper by Asa Gray, published in 1858. He 

 sent me some seeds, and on raising some plants I 

 was so much fascinated and perplexed by the 

 revolving movements of the tendrils and stems, 

 which movements are really very simple, though 



