404 CHAP. XXXV. TORSION UNDER DIFFUSE STIMULATION 



and at the base in the inverted, position. The tabulated 

 results show that in the inverted position the rate of rotation 

 invariably underwent a marked diminution ; the statolithic 

 particles now press against the apical ends of the cells, 

 which are thus shown to be the more excitable. 



Table LII. — Effect of Geotropism in Inverted Position in 



Retardation of Torsion. 



Experiment 225. Reversal of torsion. — In highly sen- 

 sitive specimens, inversion of the plant did not merely 

 retard the rate of torsion, but induced an actual reversal of 

 its direction. Thus, in a specimen of Porana the rate in the 

 erect position was 23. When inverted, the torsional move- 

 ment was found to have undergone an actual reversal to 

 negative — that is to say, the direction of torsion was now 

 with the hands of the clock, at a rate of — 5. 



In the next series of experiments, observations were 

 taken with specimens erect, then inverted, then erect again, 

 in order to eliminate the effect of any chance variation. 

 These repetitions induce fatigue, so that the response on re- 

 erection of the stem is sometimes less than at the beginning. 

 In vigorous specimens, however, there is but little decline. 

 The following table gives results obtained with a number 

 of different plants : 



Table LIII. — Geotropic Reaction in Different Positions : 

 Erect, Inverted, and Re-erected. 



