geo-electrtc response of shoot 



4r>9 



below the results of a typical experiment carried out with 

 a vigorous specimen, the response being distinguished as - 

 when A is above, and + when A is below, the inversion 

 bringing about a reversal direction of the responsive current. 



RELATION BETWEEN ANGLE OF VERTICAL ROTATION AND 

 INTENSITY OP GEOTROPIC REACTION. 



The relation between the angle of inclination and the 

 resulting geotropic action has already been determined 

 by the Method of Axial Rotation. The ratio between 

 the geotropic effects at 90° and 45° was thus found 



to be 1*49, which is nearly the same as 



Sin 90* 



I was 



next desirous of determining the relative excitations at the 

 two angles by the Method of Vertical Rotation. It is 

 necessary here to refer to certain differences of condition in 

 the two methods. In the Axial Method, the hypothetical 

 statoliths are distributed uniformly through the length of 

 the cell, and rotation round the long axis causes displace- 

 ment of the statoliths, the resulting pressure thus increasing 

 with the sine of the angle of inclination. But in the case 

 of vertical rotation through 4.")^ to the right, the statoliths 

 originally at the base of the cell accumulate to the right 

 hand corner of the cell ; a portion of the basal side of 

 the cell is thus subjected to pressure. When the angle is 

 increased to 90^ the statoliths pass along the whole length 

 including the basal and apical sides of the cell ; but the 

 excitability of the apical half may prove to be greater 

 than that of the basal half. Hence excitatory geotropic 

 effect is not likely to vary strictly as in sine of angle of 

 inclination. 



