EX HA US TIVENESS. 69 



the various conditions under which the experi- 

 ments were made. As I have elsewhere shown 

 for another more involved case, the disputant 

 observers were both right. 1 It was lack of 

 exhaustion of the logical conditions of the 

 problem that led to the contradiction. Total 

 exclusion of error requires that every move- 

 ment of the experimenter be fraught with in- 

 tention. It is fairly safe to assume that, if two 

 observers are competent and upright, their con- 

 tradictory results, no matter on what subject, 

 will prove essential to the final solution of the 

 problem. 



The publication of the " Power of Movement 

 in Plants " was followed by several years of 

 active investigation on and discussion of the 

 "Darwinian curvature" of radicles. It has 

 been shown that radicles, instead of being 

 deflected by tin-foil on soft sand, will pene- 

 trate mercury and pierce tin-foil even when 

 they strike it at a quite high angle. In expla- 

 nation of the initial error of the Darwins it has 

 been suggested that the radicles upon which 

 they experimented were wilted. It has been 

 further shown that in the experiments in which 

 they attached small hard objects to the tips of 

 the radicles to induce them to curve, the curva- 



1 Popular Science Monthly, January, 1894, pp. 373~376 



