GEOTROPIC REACTION 283 



recording surfaces. The successive dots in the records 

 may, according to different requirements, be at intervals 

 varying from 5 to 20 seconds. The records therefore not 



Fig. 165. The Quadruplex Geotropic Recorder. 



only give the characteristic curves of the geotropic move- 

 ments of different plants, but also their time-relations. 

 For certain experiments I employ the high magnification 

 of 100 times ; a smaller magnification is, however, sufficient 

 for general purposes. 



Determination of the Character of Geotropic 



Reaction 



The observed geotropic concavity of the upper side of 

 a horizontally laid shoot may be due to excitatory con- 

 traction of that side, or it may result from compression due 



