346 BOTANY [CHAP. XI 



Letter 672 Schultze, but I did not read it, for German handwriting 

 utterly puzzles me, and I am so weak, I am capable of 

 no exertion. I took the liberty, however, of asking him to 

 send me a copy, if separate ones are printed, and I reminded 

 him about the Sponge paper. 



You will have received before this my book on orchids, 

 and I wish I had known that you would have preferred the 

 English edition. Should the German edition fail to reach 

 you, I will send an English one. That is a curious obser- 

 vation of your daughter about the movement of the apex of 

 the stem of Linuui^ and would, I think, be worth following 

 out. I suspect many plants move a little, following the sun ; 

 but all do not, for I have watched some pretty carefully. 



I can give you no zoological news, for I live the life of 

 the most secluded hermit. 



I occasionally hear from Ernest Hackel, who seems as 

 determined as you are to work out the subject of the change 

 of species. You will have seen his curious paper on certain 

 medusae reproducing themselves by seminal generation at two 

 periods of growth. 



On April 3rd, 1868, Darwin wrote to F. Miiller : "Your diagram of the 

 movements of the flower-peduncle of the Alisma is extremely curious. 

 I suppose the movement is of no service to the plant, but shows how 

 easily the species might be converted into a climber. Does it bend 

 through irritability when rubbed ? " 



Letter 673 To F. M tiller. 



Down, Sept. 2$th [1866]. 



I have just received your letter of August 2nd, and am, as 

 usual, astonished at the number of interesting points which 

 you observe. It is quite curious how, by coincidence, you 

 have been observing the same subjects that have lately 

 interested me. 



Your case of the Notylia 2 is quite new to me ; but it 

 seems analogous with that of Acropera, about the sexes of 

 which I blundered greatly in my book. I have got an 



1 F. Miiller, Jenaische Zeitschrift, Bd. V., p. 137. Here, also, are 

 described the movements of Alisma. 



2 See F. Miiller, Bot. Zeitung, 1868, p. 630; Pert, of Orchids, 

 Ed. ii., p. 171. 



