208 TURNING OP FLOWERS TO THE LIGHT. 



appear about the veins on their under sides, 

 and the cuticle scales off. Succulent leaves, 

 though so thick and firm as many of them 

 are, have been observed to be peculiarly sen- 

 sible to light, while other plants, as Mallows, 

 according to Bonnet, are much less so. The 

 Miseltoe, Viscum album, Engl. Bof. t. 1470, 

 the two sides of whose leaves are alike in ap- 

 pearance, and both equally, in general, pre- 

 sented to the light, are not found to turn 

 upon any change in the posture of the branch. 

 Neither do upright sword-shaped leaves alter 

 their position, because in them both sides 

 must be presumed to perform the same func- 

 tions with respect to light as well as air. 



Mr. Calandrini found vine-leaves turned 

 to the light when separated from the stem 

 and suspended by a thread. Of this any 

 one may be easily satisfied, provided the ex- 

 periment be made with sufficient care and 

 delicacy. It is important, as demonstrating 

 the turning to be accomplished by an im- 

 pression made on the leaf itself, and not upon 

 its footstalk. 



Nor is this effect of light pecuhar to leaves 

 alone. Many flowers are equally sensible to 



