1868- 1881] DION 1 \ 395 



I will send up early to-morrow two plants [of / /] Letter 716 



with five goodish leaves, which you will know by their being 

 tied to sticks. Please remember that the slightest touch, 

 even by a hair, of the three filaments on each lobe makes 

 the leaf close, and it will not open for twenty-four hours. 

 You had better put \ in. of water into the saucers of the pots. 

 The plants have been kept too cool in order to retard them. 

 You had better keep them rather warm {i.e. temperature of 

 warm greenhouse) for a day, and in a good light. 



I am extremely glad you have undertaken this subject. 

 If you get a positive result, I should think you ought to 

 publish it separately, and I could quote it ; or I should be 

 most glad to introduce any note by you into my account. 



I hive no idea whether it is troublesome to try with the 

 thermo-electric pile any change of temperature when the leaf 

 closes. I could detect none with a common thermometer. 

 But if there is any change of temperature I should expect it 

 would occur some eight to twelve or twenty-four hours after 

 the leaf has been given a big smashed fly, and when it is 

 copiously secreting its acid digestive fluid. 



1 forgot to say that, as far as I can make out, the inferior 

 surface of the leaf is always in a state of tension, and that the 

 contraction is confined to the upper surface ; so that when 

 this contraction ceases or suddenly fails (as by immersion in 

 boiling water) the leaf opens again, or more widely than is 

 natural to it. 



Whenever you have quite finished, I will send for the 

 plants in their basket. My son Frank is staying at 6, Queen 

 Anne Street, and comes home on Saturday afternoon, but you 

 will not have finished by that time. 



P.S. I have repeated my experiment on digestion in Drosera 

 with complete success. By giving leaves a very little weak 

 hydrochloric acid, I can make them digest albumen — i.e. 

 white of egg — quicker than they can do naturally. I most 

 heartily thank you for all your kindness. 1 have been 

 pretty bad Lately, and must work very little. 



To J. Burdon Sanderson. Letter 717 



Sept. 1 1 1873]. 

 How very kind it was of you to telegraph to me. I am 

 quite delighted that you have got a decided result. Is it not 



