190 KLINOSTAT. (CH. VII 



klinostat is placed with the spindle at right angles to the 

 plane of the window, the leaves will be pointing almost 

 directly away from the light. The angular divergence 

 from the vertical of a few leaves having been noted the 

 klinostat is set in movement. After two or three days it 

 will be found that the leaves have curved towards the 

 light, and that they have come to rest in such a position 

 that the laminae are roughly vertical, i.e. at right angles 

 to the horizontal illumination from the window 1 . 



(ii) Dig up a Ficaria with a large ball of earth (so 

 that the epinastic curve cannot occur), and place it in the 

 dark, in which case the leaves will bend upwards. Leave 

 it in the dark until the leaves are about 45 above the 

 horizon, and fix it on the klinostat precisely as described 

 for (i). The leaves will now be pointing more or less 

 towards the light, and in two or three days they will have 

 curved away from the light until their blades are approxi- 

 mately vertical. 



(iii) In this experiment the klinostat stands as iD (i) 

 and (ii), but the plant is arranged so that its axis is at 

 right angles to the spindle. The leaves behave in the 

 same way as if the plant was stationary, that is to say, 

 those pointing towards the light curve downwards, while 

 those pointing away from the light move upwards until 

 the laminae of both are at right angles to incident light 2 . 



1 Strictly speaking it is the resultant of the illumination which gives 

 the effect of horizontal light. See F. Darwin, loc. cit. p. 427. 



2 Into the difficult question of the behaviour of the lateral leaves on 

 the klinostat we do not propose to enter. 



