380 



LIFE MOVEMENTS TN FLANTS 



I obtained similar results with various other creeping 

 stems. 



Fig. 140. — Photonastic curvature of creeping stem of Mimosa pudica : in the 

 central figure the stem is seen to be vertical: action of diftiise light induced 

 appropriate curvatures by greater contraction and concavity of the more excitable 

 lower or shaded side, as seen ia figures to the right(6) and left(c). 



It has been shown that under prolonged unilateral 

 stimulation, excitation becomes internally diffused ; this 

 gives rise to an effect similar to that of external diffuse 

 stimulus. Under strong light the shaded side becomes 

 concave, and thus press against the ground or the support ; 

 this will be the characteristic response of creeping stems in 

 which the shaded side is the more excitable. The facts 

 given above will probably explain the response of midribs 

 of leaves, of the creeping stem of Lysimachia, all of 

 which, in response to the action of strong light acting 



