318 BOTANY. [Oh. XVII. 



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 axe 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 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 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 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. Nevertheless the bending of this lower part, as 

 I conclude from my experiments with opaque caps, is in- 

 fluenced by the action 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. 



Independently of the question of transmission, my mind is 

 so full of facts leading me to believe that light, gravity, &c, 

 act not in a direct manner on growth, but as stimuli, that I am 

 quite unable to modify my judgment on this head. I could 

 not understand the passage at jk 78, until I consulted my 

 son George, who is a mathematician. He supposes that your 

 objection is founded on the diffused light from the lamp 

 illuminating both sides of the object, and not being reduced, 

 with increasing distance in the same ratio as the direct light ; 

 but he doubts whether this necessary correction will account for 

 the very little difference in the heliotropic curvature of the 

 plants in the successive pots. 



With respect to the sensitiveness of the tips of roots to 

 contact, I cannot admit your vie~ff until it is proved that I am 

 in error about bits of card attached by liquid gum causing 



