186 



KLINOSTAT. 



[CH. VII 



at right angles to incident light is replying in a specific 

 manner to stimulation, just as a positively heliotropic 

 stem reacts in its specific way by placing itself parallel to 

 incident light. 



To illustrate this fact, plants must be subjected to 

 one-sided illumination while kept in slow rotation on the 

 klinostat. 



We use the instrument designed by Mr H. Darwin 

 and described by one of us 1 in the year 1880. 



The instrument is shown in fig. 36 ; the plant in a 



-~dr 



FIG. 36. Exp. 217. Copied from the Linnean Society's Journal, 1880. 



flower-pot is fixed in a wooden box B, which again is 

 secured by the thumb-screw th to the plate pi : the box 

 being cubical can be fixed either as shown in the figure 

 or with the axis of the flower-pot at right angles to the 

 spindle (k) of the klinostat. The plate pi is attached 

 to the spindle k, which ends in a point turning in the 



1 Francis Darwin, Linnean Society's Journal, Vol. xvur. p. 4?0. The 

 original klinostat is described by Sachs in his Arbeiten, n. p. 214. 



