460 LIFE MOVEMENTS IN PLANTS 



Whatever the reason may be, I find as a result of 

 experiments with 12 different specimens that the mean 

 ratio of the effects at 90' and 45°, obtained by the Method 

 of Vertical Rotation, is 1*8 : 1 which is greater than 1*J^9 : 1 

 obtained by the Method of Axial Rotation, this latter 

 value being practically the same as ^^7-. . 



SUMMARY. 



It is shown that the state of excitation under direct 

 stimulus is exhibited by an electrical change of galva- 

 nometric negativity ; tho eft'ect of indirect stimulus induces, 

 on the other hand, an electrical ch mge of galvanometric 

 positivity. The negative electric change corresponds to 

 contraction and diminution of turgor ; the positive electric 

 change indicates, on the other hand, an expansion and 

 increase of turgor. 



The electric response to geotropic stimulus is studied 

 by the two methods of Axial and Vertical Rotation, The 

 upper side of a horizontally laid shoot is found to undergo 

 an excitatory change of galvanometric negativity. 



In quick reacting organs the latent period of geo-electric 

 response is about 5 seconds, and the maximum excitation 

 is induced in the course of 2 minutes. 



The geo-electric response is due to physiological reaction. 

 The intensity of response declines with age and is abo- 

 lished at the death of the plant. 



Under symmetrical conditions, the intensity of geotropic 

 reaction is found proportional to the sine of the angle of 

 inclination. 



Electric investigation shows that the lower half of the 

 pulvinus of Mimosa is geotropically more excitable than 

 the upper halt. 



