MOVEMENTS OF PLANTS 49 



plan) or vice versa, as^in the feminine way of 

 threading a needle. In other cases you create what 

 is practically a new machine by inversion, as in 

 a certain apparatus in which the hand of a clock 

 stops still while the clock itself rotates. The effect 

 is still more striking with my plants, for the inver- 

 sion practised on them entirely changes the character 

 of their movement. 



The result may be shown with the seedling 

 Setarias of which I have spoken, or with Sorghum, 

 as in Fig. 4. If one of these is supported by its seed 

 with its stem projecting freely in the horizontal 

 plane, the gravitation stimulus makes it bend 

 upwards until the tip is vertical, when the stimulus 

 ceases to act and the curvature comes to an end. 

 If the conditions are reversed, if the seedling is 

 supported in a horizontal position by its tip, while 

 the seed projects freely, the result is at first the 

 same, though finally it comes to be strikingly 

 different. The basal end of the seedling is carried 

 upwards by the curvature of the stem ; but 

 according to the theory we are testing, the tip of the 

 seedling is the only part of the plant which feels 

 the gravitational stimulus, and the tip of the 

 seedling remains horizontal in spite of the curvature 

 of the stem. Therefore the tip of the seedling is 

 not freed from stimulation as it was in the first 

 case, where the curvature brought the tip into the 

 vertical position. The horizontal tip therefore 

 continues to send commands to the stem to go on 

 curving, in a way I can best explain if I am allowed 

 to make the plant express its sensations in words. 

 The tip says to the stem, "I am horizontal, therefore 



