XLIV.— ON GEOTROPKJ T0R8I0N 



Bll 



Sir J. ('. HosK, 



Assisted bij 



GURUPRASANNA DaS. 



I HAVE explained that in a dorsiventral organ, lateral 

 application of various stimuli induces a respon?iive torsion 

 by which the less excitable side is made to face the sti- 

 mulus (p. 403). I shall in this chapter show that the 

 effect of stimulus of gravity is in every respect similar to 

 other forms of stimulation. 



The direction of force, of gravity is fixed, and we have 

 to arrange matters in such a way ih^^t the geoiropic sti- 



t'lG. 179. — Diaojram of arrangement for torsional response innler geotropic 

 stimulus. The less excitable upper half of pulvinus is, in the above figure, to 

 the left and the torsional response is clockwise 



mulus should act on the dorsiventral organ in a lateral 

 direction. In the following experiments the pulvinus of 



37 



