326 CLIMBING AND [l374- 



observed this fact, or believe it on good authority. I also 

 wish to know what proportion by weight the atropine bore 

 to the water of solution, and how much of the solution was 

 applied to the eye. The reason why I am so anxious on this 

 head is that it gives some support to certain facts repeatedly 

 observed by me with respect to the action of phosphate of 

 ammonia on Drosera. The 4000000 °f a g ra i n absorbed by 

 a gland clearly makes the tentacle which bears this gland 

 become inflected ; and I am fully convinced that ^oooVooo" °f 

 a grain of the crystallised salt (i.e. containing about one-third 

 of its weight of water of crystallisation) does the same. Now 

 I am quite unhappy at the thought of having to publish such 

 a statement. It will be of great value to me to be able to 

 give any analogous facts in support. The case of Drosera is 

 all the more interesting as the absorption of the salt or any 

 other stimulant applied to the gland causes it to transmit a 

 motor influence to the base of the tentacle which bears the 

 gland. 



Pray forgive me for troubling you, and do not trouble your- 

 self to answer this until your health is fully re-established. 



Pray believe me, 



Yours very sincerely, 



Charles Darwin. 



[During the summer of 1874 he was at work on the genus 

 Utricularia, and he wrote (July 16th) to "Sir J. D. Hooker 

 giving some account of the progress of his work : — 



" I am rather glad you have not been able to send Utricu- 

 laria, for the common species has driven F. and me almost 

 mad. The structure is most complex. The bladders catch 

 a multitude of Entomostraca, and larvae of insects. The 

 mechanism for capture is excellent. But there is much that 

 we cannot understand. From what I have seen to-day, 

 strongly suspect that it is necrophagous, i.e. that it cannot 

 digest, but absorbs decaying matter." 



