336 'POWER OF MOVEMENT [l88r. 



C. Darwin to Julius Wiesner. 



Down, October 25th, 1881. 



MY DEAR SIR, I have now finished your book,* and have 

 understood the whole except a very few passages. In the 

 first place, let me thank you cordially for the manner in which 

 you have everywhere treated me. You have shown how a 

 man may differ from another in the most decided manner, 

 and yet express his difference with the most perfect courtesy. 

 Not a few English and German naturalists might learn a 

 useful lesson from your example ; for the coarse language 

 often used by scientific men towards each other does no good, 

 and only degrades science. 



I have been profoundly interested by your book, and some 

 of your experiments are so beautiful, that I actually felt 

 pleasure while being vivisected. It would take up too much 

 space to discuss all the important topics in your book. I fear 

 that you have quite upset the interpretation which I have 

 given of the effects of cutting off the tips of horizontally 

 extended roots, and of those laterally exposed to moisture ; 

 but I cannot persuade myself that the horizontal position of 

 lateral branches and roots is due simply to their lessened 

 power of growth. Nor when I think of my experiments with 

 the cotyledons of Pkalaris, can I give up the belief of the 

 transmission of some stimulus due to light from the upper 

 to the lower part. At p. 60 you have misunderstood my 

 meaning, when you say that I believe that the effects from 

 light are transmitted to a part which is not itself heliotropic. 

 I never considered whether or not the short part beneath the 

 ground was heliotropic ; but I believe that with young seed- 

 lings the part which bends near, but above the ground is 

 heliotropic, and I believe so from this part bending only 

 moderately when the light is oblique, and bending rectan- 

 gularly when the light is horizontal. Nevertheless the bending 



* 'Das Bewegimgsvermogen der Pflanzen.' Vienna, 1881. 



