Chap. XI. TRANSMITTED EFB^ECTS : CONCLUSION. 545 



the attraction of gravity has an important bearing on 

 the theory of geotropism. Authors seem generally to 

 look at the bending of a radicle towards the centre of 

 the earth, as the direct result of gravitation, which is 

 believed to modify the growth of the upper or lower 

 surfaces, in such , a manner as to induce curvature in 

 the proper direction. But we now know that it is the 

 tip alone which is acted on, and that this part trans- 

 mits some influence to the adjoining parts, causing 

 them to curve downwards. G-ravity does not appear 

 to act in a more direct manner on a radicle, than it 

 does on any lowly organised animal, which moves 

 away when it feels some weight or pressure. 



