GEO-ELECTRIC RESPONSE 



437 



of the present chapter, to submit to independent examina- 

 tion by means of electrical response. 



I have already shown that 

 the unilateral pressure of par- 

 ticles on the growing organ is 

 effective in inducing curvature 

 in such a way that the side 

 acted upon becomes concave. 

 This experiment was carried 

 out by subjecting one side of 

 a growing organ to the pres- 

 sure of iron particles, which 

 were pressed against it by the 

 action of an electro-magnet on 

 the opposite side (fig. 266). 

 The magnetic particles in this 

 case functioned as virtual 

 statoliths, and a curvature was 

 induced by the excited side 

 becoming concave (fig. 267). 



There is, however, one difficulty in connection with the 

 statolithic theory of stimulation. When the stem is held 

 erect the particles rest on the bases of the cells, and their 

 general distribution on 

 the two sides of the 

 organ is symmetrical. 

 Asymmetry of distri- 

 bution is induced, how- 

 ever, when the shoot is 

 laid horizontally, and 



Stimulation might be ex- FIG. 267. Record of Responsive Curvature 

 ,' r .. . , . . Induced in Bud of Crinum Lily by Uni- 



pected to iollOW Within lateral p ress ure of Particles 



a very short time, since 



the displacement of particles from base to side cannot take 

 long. This being so, the geotropic curvature of the shoot 

 upwards should take place within a short time. But, instead 

 of this, we find that the curvature is at first downwards ; and 



FIG. 266. Diagrammatic Repre- 

 sentation of Experiment showing 

 Curvature Induced by Unilateral 

 Pressure Exerted by Particles 



F, flower-bud of Crinum ; s, india- 

 rubber strip studded with iron 

 particles attracted by electro- 

 magnet, M, causing unilateral 

 pressure on growing region ; I, 

 index attached to flower. 



