SUMMARY 173 



Summary 



By the application of sensitive physiological tests, 

 gradation of excitability has been discovered in the layers 

 of tissue in the pulvinus of Mimosa. 



In an organ with pronounced physiological anisotropy, 

 in which the distal lower is far more excitable than the 

 upper or proximal side, stimulation of the proximal side is 

 followed by a transverse conduction of excitation which 

 brings about a greater contraction of the lower side. The 

 sequence of response is then positive, neutral, and very 

 pronounced negative. The terms proximal and distal are 

 used in the sense of stimulated and unstimulated sides. 



When the stimulus is applied on the more excitable 

 lower side of the organ, the result is a predominant con- 

 traction of that half ; the resulting curvature cannot be 

 neutrahsed by transverse conduction of excitation to the 

 feebly excitable distal side. 



The phototropic and photonastic movements are not 

 unrelated phenomena, but there is continuity between them. 



