LEAVES WITH BEGABD TO LIGHT. 



431 



Table II.* 



Date. 



Leaf i. Leaf ii. 



Leaf iii. 



Lamina. 



Petiole. 



Lamina. 



Petiole. 



Lamina. 



Petiole. 



April 17, 1 



4 P.M. j 



April 19, 1 

 8.25 a.m. J 

 April 20,1 

 8.45 a.m. J 



-90 ca 

 + 10 

 + 



-90 ca 

 +20 -25 

 +20 ± 



o 

 +10 



+ 15 



-90 ca 



-20 



-12 



o 

 -20 



— 22 



Thus two of the three leaves had gained the diaheliotropic 

 plane " (that is, became at right angles to the light, see p. 429), and 

 the third leaf (iii.) was only 12° behind that plane. 



This experiment proves that the leaves are able to place them- 

 selves at right angles to the light without the aid of apogeotro- 

 pismf. If when the plant is not on the klinostat, but grow- 

 ing in the normal position, the horizontal position is the result of 

 apheliotropism balanced by apogeotropism, then in the above 

 experiment (Exp. 1) the leaves ought to have remained in the 

 position -90° into which epinasty had brought them— that is, the 

 petiole and lamina pointing away from the light. 



But it may be objected that epinastically bent leaves tend to 

 recover a normal position independently of the direction of light. 

 The following experiment shows that this is not the case. 



Experiment 3.— A plant, whose leaves were bent epinastically 

 backward., was pinned (April 6th, 3.8 p.m.) inside a tin box; so 

 that the plant was in complete darkness. The positions of the 

 leaves having been noted, the box was fixed to the klinostat 

 so that the axis of the plant was parallel to the axis of rotation. 



Table III. 



* Where the measurements were for any reason taken somewhat roughly 

 ca, abbreviation for -circa" = "about," is added, as in the upper line of 



^fwicaria sometimes exhibits well-marked sleep movement* of the younger 

 leaves,* which rise far above the horizon at night. These movements were well 



