i860.] INSECTIVOROUS PLANTS. 319 



no change on the four in water ; every gland and hair affected 

 in those in ammonia. 



" I had measured the quantity of weak solution, and I 

 counted the glands which had absorbed the ammonia, and 

 were plainly affected ; the result convinced me that each 

 gland could not have absorbed more than -Q^^Q or -g-^yoo" f 

 a grain. I have tried numbers of other experiments all 

 pointing to the same result. Some experiments lead me to 

 believe that very sensitive leaves are acted on by much 

 smaller doses. Reflect how little ammonia a plant can get 

 growing on poor soil yet it is nourished. The really sur- 

 prising part seems to me that the effect should be visible, 

 and not under very high power ; for after trying a high power, 

 I thought it would be safer not to consider any effect which 

 was not plainly visible under a two-thirds object glass and 

 middle eye-piece. The effect which the carbonate of ammonia 

 produces is the segregation of the homogeneous fluid in the 

 cells into a cloud of granules and colourless fluid ; and 

 subsequently the granules coalesce into larger masses, and for 

 hours have the oddest movements coalescing, dividing, 

 coalescing ad infinitum. I do not know whether you will 

 care for these ill-written details ; but, as you asked, I am sure 

 I am bound to comply, after all the very kind and great 

 trouble which you have taken." 



On his return home he wrote to Sir J. D. Hooker 

 (November 21, 1860) : 



" I have been working like a madman at Drosera. Here 

 is a fact for you which is certain as you stand where you 

 are, though you won't believe it, that a bit of hair yg^oo" f 

 one grain in weight placed on gland, will cause one of the 

 gland-bearing hairs of Drosera to curve inwards, and will alter 

 the condition of the contents of every cell in the foot-stalk of 

 the gland." 



And a few days later to Lyell : 



" I will and must finish my Drosera MS., which will take 



