LEAVES WITH EEGABD TO LIGHT. 



Fig- 7. 



435 



Diagrams illustrating Experiment 7. 

 Fig. 7 shows the position of the leaves on March 25 ; fig. 8 on March 28 : 1 1, 

 the transverse plane ; x, the axis of the plant ; P i and P ii the petioles of 

 leaves i. and ii. ; L i and L ii the laminae. The arrows give the direction 

 of the light. 



These movements are shown in the diagrams : fig. 7 represents 

 the position of the leaves on March 25th ; fig. 8 on March 28th. 



Another similar experiment gave somewhat different results. 

 In this case it was the leaf pointing towards the light (correspond- 

 ing to L i in fig. 7), which failed to place itself exactly in the dia- 

 heliotropic plane, though it moved in the right direction. 



Experiment 8. — A plant had been grown a short time in the 

 dark, and was not etiolated ; the two youngest leaves (i. being 

 the older) had grown up highly inclined above the horizon. It 

 w*as then (April 2nd) placed on the klinostat in the lateral posi- 

 tion with the morphologically under surface of i. facing the light. 

 It will be seen that both leaves began to curve in the epinastic 

 direction, i. curving towards the light and ii. away from it. The 

 positions which the leaves ultimately assumed at the end of 

 the five days during which the experiment lasted are not in the 

 diaheliotropic plane ; to reach this, i. would have to move from 

 — 15° to —90°, and ii. from +52° to +90°. It is unfortunate 

 that the experiment was not continued longer, as the leaves would 

 possibly have become more truly at right angles to the light. It 



LINN. JOTJB.N. — BOTANY, VOL. XVIII. 2 K. 



