370 BOTANY [CHAP. XI 



Leiter 692 which, though of no importance, has been largely read in 

 England. I have little or nothing to tell you about myself. 

 I have for a couple of months been observing the effects of 

 carbonate of ammonia on chlorophyll and on the roots of 

 certain plants, 1 but the subject is too difficult for me, and I 

 cannot understand the meaning of some strange facts which I 

 have observed. The mere recording new facts is but dull work. 

 Professor Wiesner has published a book, 2 giving a different 

 explanation to almost every fact which I have given in my Power 

 of Movement in Plants. I am glad to say that he admits that 

 almost all my statements are true. I am convinced that many 

 of his interpretations of the facts are wrong, and I am glad to 

 hear that Professor Pfeffer is of the same opinion; but I believe 

 that he is right and I wrong on some points. I have not the 

 courage to retry all my experiments, but I hope to get my son 

 Francis to try some fresh ones to test Wiesner's explanations. 

 But I do not know why I have troubled you with all this. 



Letter 693 To F. M tiller. 



[4, Bryanston St.], Dec. igth, 1881. 



I hope that you may find time to go on with your experi- 

 ments on such plants as Lagerstrosinia, mentioned in your 

 letter cf October 29th, for I believe you will arrive at new 

 and curious results, more especially if you can raise two sets 

 of seedlings from the two kinds of pollen. 



Many thanks for the facts about the effect of rain and mud 

 in relation to the waxy secretion. I have observed many 

 instances of the lower side being protected better than the 

 upper side, in the case, as I believe, of bushes and trees, so 

 that the advantage in low-growing plants is probably only an 

 incidental one. 3 As I am writing away from my home, I 



1 Published under the title " The Action of Carbonate of Ammonia on 

 the Roots of Certain Plants and on Chlorophyll Bodies," Linn. Soc.Journ., 

 XIX., 1882, pp. 239-61, 262-84. 



2 See Letter 763. 



3 The meaning is here obscure : it appears to us that the significance 

 of bloom on the lower surface of the leaves of both trees and herbs 

 depends on the frequency with which all or a majority of the stomata 

 are on the lower surface where they are better protected from wet (even 

 without the help of bloom) than on the exposed upper surface. On the 

 correlation between bloom and stomata, see Francis Darwin Limi., Soc. 

 Journ., XXII., p. 99. 



