434 



ME. F. DARWIN ON THE POSITION OF 



Table VI. 



Leaf i. 



Leaf ii. 



Lamina. 



Petiole. 



Lamina. 



Petiole. 



April 2, 1 R R 

 3 45 p.m. )[ ~ 80 



April 5, 1 _ 20 

 4.30 p.m. ; zu 



April 6, \ _ 1Q 



10.20 a.m. I i 1U 

 1 



o 



-25 



*- 8 chd 



— 7 chd 



o 

 +60 



+ 15 



+ 6 



o 1 

 +45 chd 



+30 chd 



+30 



* For explanation of chd, see note to Table IV. 



This experiment shows that one leaf may approach the diahelio- 

 tropic plane by moving away from the light, while another on 

 the same plant may do the same by moving towards it. It shows 

 once more that the leaves of Ranunculus Ficaria place themselves 

 at right angles to the light when freed from the stimulus of 

 gravitation. 



The following experiments show the power possessed by the 

 leaves of adapting themselves to lateral illumination. 



Experiment 7.— A plant was placed (March 25th) in the lateral 

 position on the klinostat before a south-west window, where it 

 was shaded as far as possible from direct sunlight in the evening. 

 Leaf i. pointed (i. e. the axis of the petiole and of the midrib 

 was directed) nearly towards the window ; ii. pointed away from 

 the window. 



Table VII. 



Date. 



Leaf i. 



Leafii. 



Lamina. Petiole. 



Lamina. 



Petiole. 



March 25, "1 



3 P.M. J 



March 27, 1 

 6.15 p.m. J 



March 28, j 

 9.55 a.m. j 



- 3° - 3° 

 i -45° 



-60° ca 



o 

 -10 



+45 



+42 



-80° -30° 



+42° 



Thus leaf i. bent epinastically downwards until the lamina was 

 —80°, which, when the plant is in the lateral position, is nearly 

 at right angles to the light. The lamina of leaf ii. moved 

 through more than 100° in its attempt to reach the diaheliotropic 

 plane. 



