CH, VIl] 



DIAGEOTROPISM. 



in 



poetims by using either flowers attached to the plant or 

 cut specimen placed in water as shown in fig. 37. 



Fig. 37. Exp. 223. 



Select a specimen in which the scape is vertical and 

 the corolla tube approximately horizontal: place it (not 

 necessarily in the dark) in a position so that the 

 corolla tube is 45° below the horizon. The curvature 

 of the flower scape will begin to diminish and the corolla 

 tube will ultimately become once more horizontal as 

 shown in figure, in which the dotted line D gives the 

 position from which the flower has risen. The angle 

 made by the corolla with the horizon may be roughly 

 measured, as shown in the figure, by means of a graduated 

 semicircle of cardboard Q to the centre of which a 

 plummet P is suspended. The zero should be in the 

 centre of the arc and the graduations should run from 

 0° to 90° in either direction. 



12—2 



