TURNING OF FLOWERS TO THE LIGHT. 159 



delicacy. It is important, as demonstrating the turning 

 to be accomplished by an impression made on the 

 leaf itself, and not upon its footstalk. 



Nor is this effect of light peculiar to leaves alone. 

 Many flowers are equally sensible to it, especially the 

 compound radiated ones, as the Daisy, Sun-flower, 

 Marigold, See. In their forms Nature seems to have 

 delighted to imitate the radiant luminary to which they 

 are apparently dedicated, and in the absence of whose 

 beams many of them do not expand their blossoms 

 at all. The stately Annual Sun-flower, Heliauthus 

 annuus, displays this phaenomenon more conspicuously 

 on account of its size, but many of the tribe have 

 greater sensibility to light. Its stem is compressed in 

 some degree, to facilitate the movement of the flower, 

 which, after following the sun all day, returns after 

 sun-set to the east, by its natural elasticity, to meet his 

 beams in the mornin<:j. Dr. Hales thought the heat of 

 the sun, by contracting the stem on one side, occa- 

 sioned the flower to incline that way ; but if so, it 

 would scarcely return completely at night. There 

 can be no doubt, from the observation of other similar 

 flowers, that the impression is made on their radiated 

 florets, which act as wings, and seem contrived chiefly 

 for that purpose, being frequently destitute of any 

 other use. A great number of leaves likewise follow 

 the sun in its course ; a clover-fleld is a familiar in- 

 stance of this. 



Of all leaves those of pinnated leguminous plants 



