RESrONSIVE CURVATURES — NEGATIVE GEOTROPISM 50I 



The first record was taken after the curvature movement, 

 due to gravitation at an angle of 45°, had attained a constant 

 vakie. The tip of the flower was then found to be moving 

 at a rate of four divisions per minute. On changing the 

 angle to 135°, the rate of movement showed an imme- 

 diate increase, and attained in the course of five minutes 

 a permanent rate of I5'S divisions per minute. It has been 

 said that the experimental adjustment of change of position 

 took only about a minute 

 to effect, yet on renewing 

 the record we find that the 

 effective increase thus esta- 

 blished in the gravitation- 

 stimulus was immediately 

 perceived and responded 

 to by the organ, in an 

 accelerated rate of curva- 

 ture. The permanent in- 

 creased rate at 135° is thus 

 found to be nearly four 

 times that at 45°. The 

 organ was now returned 

 to its position at 45°, and 

 the rate once more fell till 

 it became nearly equal to 

 what it had originally been 

 at 45°, being only very 

 slightly greater. The organ 

 was once more placed at 135°, and the rate again rose, till it 

 reached slightly beyond its former value at that angle. The 

 ratio of the second rates determined at 45° and 135° was also 

 found to be almost as i is to 4 (fig. 208). 



With reference to the cause of this difference of gravita- 

 tional effect, Haberlandt .suggested that it may lie in the 

 fact that the weight of the statoliths in 45° position is on the 

 basal half, while at 135° it is on the apical half (fig. 209) 

 The next point is, to account for the greater reaction of the 



Fig. 208. Response Records showing Dif- 

 ferences in Rate of Curvature according 

 as Specimen is held at Angles of 45° 

 and 135° 



