]gO CAUSE OF MOTION IN PLANTS. 



them in the sketch, had I not been fearful, b - mi- ing them 



•with the spiral wire, to make such confusion, they would 



not be known one from the other. But it is easy to under? 



stand, that by crossing vessels they are retained in their 



present situation. 



Seminal leave* I must now mention a circumstance, which helps greatly 



wire n ° ^^ * n m y rnm( l to P rov ! e J that the spiral is the cause of motion. 



It is that in the seminal /eaves there is no spiral wire; and 



in the seminal leaves there is no motion whatever.* In de<- 



scribing the spiral wire 1 did not mention the case, in which 



it is confined, because 1 wished at the same time to give a 



sketch of it to avoid confusion. It will now be found in 



Plate IV, fig. 4. 



Dmseraac:iulis J might -add to the three plants I have given many others, 

 Tery curious. . ■ \i- . . , ' . . , . ... _,. , 



in which the spiral wire distinguishes itself, i he droserq. 



acaulis is entirely governed by the spiral wire, which enters 

 the hairs, or rather arms of the leaf, and the moment a fly 

 touches it, it collapses, confining it within its circle; or 

 should the fly escape the first arm, the point leaves so viscid 

 a humour, that the next is sure to be caught. This is in- 

 finitely more curious in its formation than the dionea mus- 

 cipula; which is also governed by the spiral wire turning 

 over a ball like the mimosa, and drawing the leaves together 

 in the same manner. But drosera is managed in a more 

 peculiar way, and well worthy a drawing, which I will give 

 in my next. 

 Z,eatheriike I hope to be perfectly understood, in giving an account of 



substance the that which regulates the mo//on o/* p/iiwte, that the leather- 



lame ma'ter . ° . . 



•with the "spiral like substance, and the spiral icire, are the same matter. The 



t * r:re * thickness of the first balancing the force the second gains 



by its spiral form ; and the latter gains much firength also 



from the case that encloses it. 



"Recapitulation Before I close this letter you will excuse my recapitula- 



•f the proofs. tin ^ the pr00 f s brought forward in it and the former. The 



spiral wire is found in every leaf that has motion; in no leaf 



that, does not move ; in no firs, grasses, sea-weed, except 



confervas, and the confervas alone of all the tribe have motion. 



It is found in no chenopodinms, salsolas, or ice plants. In 



leaves that have no other motion than toward the stem and 



£>ack again, the spiral wire occurs only in the midrib of the 



leaf. 



