48 



the existing ends of the roots, not the new 

 growth, have all turned short downward 

 toward the light, and that not from 

 flaccidity or drooping. And even in the 

 denser medium of water, if the end of a 

 root is accidentally turned upward, its new 

 growth will immediately turn perpendi- 

 cularly downward. 



And, from an admirable experiment of 

 Knight, both the ascent of the stem and 

 the descent of the root would appear to 

 depend on gravitation ; for when he 

 subjected growing beans to a horizontal 

 centrifugal force superior to gravity, their 

 roots grew from, and their stems towards, 

 the centre, and the whole growth of the- 

 plants was horizontal. But, suppose this 

 to be so : the root should obey, 



and the stem disobey, the otherwise 

 universal law of gravitation, would still 

 puzzle our philosophy, as I said be- 

 fore. I have hitherto been unable to 

 get a copy of Mr, Knight's work, and 



