176 



INJURY. 



[CH. VII 



Fig. 32. Exp. 206. 



(206) Recovery from the effect of amputation. 



If the roots in exp. 205 (p. l7o) are allowed to remain 

 undisturbed for 3 or 4 days, the growing point is re- 

 generated and the roots recover the 

 power of geotropic curvature. They 

 will grow into an S-like form, because 

 until the growing point is regene- 

 rated they continue growing horizon- 

 tally or obliquely in the direction 

 Impressed on them by the geotropic 

 curvature induced before amputation. 

 When the power of reacting to the 

 gravitation-stimulus is restored they 

 curve downwards. Fig. 82^ shows this 

 state of things, L indicates the side of 

 the seedling which was downwards while the root was 

 horizontally extended, AB shows the strong induced 

 curvature, BC the second geotropic curvature occurring 

 after regeneration of the root-cap. 



(207) Curvature induced hy contact, injury, dx.^. 



If the tip of a bean root is amputated by an oblique 

 cut with a razor, so that the growing point is laterally 

 injured, the root curves away from the injured side. The 

 beans should be pinned to the lid of a jar and may be 

 grown either in damp air or with the tips in water. It is 

 imjDortant that the temperature should not exceed 16° C. 



A similar curvature may be produced by contact. 



Minute squares (lo mm. x 1*5) of cardboard or of very 



1 Poiver of Movement, fig. 195, p. 527. 

 ~ Ibid., Chap. iii. 



