REACTIONS AT 45° AND 90° 



351 



Experiment 187. — I obtained a series of galvanometric 

 responses with a petiole of Tropaeolum when rotated 

 through the entire cycle of inclination from the vertical 

 to 45° (as read by the movement of the index), back to 

 zero and then to — 45°, and back once more to zero. The 

 same procedure was followed in the case of inclination at 

 90°. The records are given in fig. 206; the response to 

 inchnation of + 45° is seen as an up-curve, with subsequent 

 recovery on return to the vertical. Inchnation of — 45° 

 evoked a reverse response of down-curve, with subsequent 

 recovery. Inclinations of + 90° and - 90° evoked re- 

 sponses of larger amplitude. The ratio of reactions at 

 90° and 45°, as determined by the amphtude of responses, 

 came out in this case as i : i • 5. The ratio of sin 90° : sin 45° 



is I : 1-41. 



The following table embodies the reactions observed 

 at 45° and 90° in six different specimens of the petiole of 

 Tropaeolum : 



Table XXVII. — Excitatory Reactions at Inclinations of 

 45° AND 90° (Petiole of Tropaeolum). 



The ratio of excitatory reaction at the two angles is 

 I -44, while the ratio of the sines is i -41. It will be noted 

 that there is a persistent small difference between the 

 two ratios, the excitation at the larger angle being greater 

 than the value deduced from the ratio of the sines. The 



