338 BOTANY. [ch. xvn. 



merit in Plants by an accomplished botanist, Dr. Julius 

 Wiesner, Professor of Botany in the University of Vienna : 



C. D. 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 lan- 

 guage 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 horizon- 

 tally extended roots, and of those laterally exposed to moist- 

 ure ; but I cannot persuade myself that the horizontal posi- 

 tion of lateral branches and roots is due simply to their 

 lessened power of growth. Nor when I think of my experi- 

 ments with the cotyledons of Phalaris, 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 misunder- 

 stood 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 seedlings 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 rectangularly when the light is horizontal. Never- 

 theless the bending of this lower part, as I conclude from 

 my experiments with opaque caps, is influenced by the ac- 

 tion of light on the upper part. My opinion, however, on 

 the above and many other points, signifies very little, for I 

 have no doubt that your book will convince most botanists 

 that I am wrong in all the points on which we differ. 



* Das Bewegungsvermugen der Pflanzen. Vienna, 1881. 



