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The mecha- 

 nism of the 

 p©lygal«. 



The flower 

 dilates and 

 ••ntracts. 



OTf THE MECKANUM OE FLOWER!. 



contemplation of a pliilosophic mind: and when it is con- 

 sidered what a quantity of plants there are, and that each 

 species has its appropriate contrivance, what an idea does it 

 give us of the Creator of all ! 



1 shall begin with the mechanism of the polygalae, all the 

 species of which are, I believe, managed in the same way. 

 To defend the stamen and pistil, till the seed is to be im- 

 pregnated, a hood covers them ; but as it is also necessary, 

 that the sun should, at the same time, shine on the female, 

 the hood has a gatherer behind, see PI. 1 1 1, tig. I, a a, to raise 

 or depress it. When the sun appears, the contraction of 

 this gatherer, in which runs the spiral wire, draws back the 

 hood as at fig. 2. b b is a. small ball, on which it turns a« 

 on a swivel. When it falls back, the drops appear on the 

 pistil, and are seen saturated with the powder of the stamen ; 

 but if a cloud should in the mean time obscure the sun, 

 and the wind rise, the gatherer behind would directly be 

 lengthened, the hood return to its place, and the drops of 

 the pistil retire within the orifice. 



How often have 1 watched this beautiful process ! Seated 

 on the ground I have at pleasure made the hood rise and 

 fall by the help of the sun, and a wet napkin, alternately 

 admitted over it ; thus viewing all its mechanical wonderft 

 at once. 



The wings, represented at fig* 2, 3, 4, have also a part 

 which contracts and dilates, fig. 3, dd. The spiral wire; 

 meeting at *e, fig. 4, is fastened to the exterior edge of 



is then collected and drawn together to a sort of pin, round 

 vhich it winds, while the outside part, fig. 3, dd, gathers 

 up like a gatherer, and throws the wing from it, or draws it 

 near the body, alternately, as fine weather, or bad require^ 

 it ; as the part X/" will necessarily open it by the contraction 

 of the spiral wire, and throw it from the body of the flower 

 to admit the suu to the seeds, that they may be perfected 

 by its rays. 



On examining a flower this effect will be easily seen. 

 The lengthening of the filaments also serves to keep the 

 hood on, when the wind blows; but when the sun shines, 

 they contract, and the hood is again at liberty to retire. 



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