THE MANIFESTATIONS OF LIFE 



65 



of growth obeyed the laws of centrifugal force and the 

 shoot grew toward the centre of attraction and its root 

 away from it. When the wheel was revolved in a hori- 

 zontal plane, the force of gravity not being overcome, 

 the plant being subjected simultaneously to both centrif- 

 ugal force and that of gravitation, took an intermediate 

 position, directing the shoot upward and toward the 

 centre, the root downward and away from it. 



It is a common observation that plants that have 



I 



HI 



FIG. 15. The movements by which a flower of Aconitum napellus regains its 

 proper position when the axis bearing it (s) is inverted. I. Inverted position; 

 II. position resulting from geotropism, the flower facing the parent axis; III. 

 flower again facing outward, after the exotropic movement. (Strasburger, 

 Noll, Schenek and Karsten.) 



made a false start, through accidental circumstance 

 or intentional interference, adjust themselves to the 

 geotropic influences by certain curvatures that result 

 from increased growth of one side and retarded growth 

 of the opposite side, the region of greatest growth being, 

 in general, that of greatest curvature. This applies 

 both to the negatively geotropic stems and the positively 

 geotropic roots. As soon as the unequal growth succeeds 

 in establishing the upright position, it ceases and sym- 

 metrical growth progresses. 



Lateral geotropism is best exemplified in climbing 

 5 



