ISq mechanism op L£AF«&TALR£. 



size of the part'that joins the stein, which at one tiineof the 

 year is but little larger, and shows the gathere* but poorly. 

 There appears a regular gradation of mechanism in this 

 part of all plants, from those which, having tho leaves per- 

 fectly sessile, are fastened in such a manner to the stem, att 

 to be absolutely incapable of turning, or moving in any 

 manner,- to those plants, the leaves of which move with a 

 touch, and the mechanism of which I hare before described 

 in the mimosa sejisitivaf. 

 Mechanism I have already with indefatigable pains traced this grada- 



mcreasing jj^j^ through 130 genera of plants, differing as much as 

 from the firs to .,,,.. i c •,, V- , i 



the mimosas. Bossible, selecting m each a tew to illustrate this truth, and 



in which the mechanism increases gradually from the firs, 

 the leaves of which move not, and have therefore no spiral 

 wire, to the mimosa, which has it knotted and turned over 

 balls. 



The first degree of motion in the peduncle is caused by 

 the simple spiral wires in their cases passing into every di- 

 minutive vessel in the leaf. The motion is then as simple 

 as the raean«, and the leaf is merely drawn nearer, or falls 

 farther from the stalk : but when the spiral wire is doubled 

 or crossed, there appears sonfie diversity of motion, by the 

 leaf not only advancing and retiring, but being able to be 

 Most plants drawn on one side. The nest gradation is shown by the 

 haTe gather- increase of the peduncle next the stalk, and this increase I 

 have ventured to call the gatlierer, because it contracts and 

 dilates to favour the spiral wire. When this is found dou- 

 ble, that is, adjoining the leaf, as well as the stem, the 

 motion is very greatly increased, since each of them moves 

 through the third of a circle, as [ shall presently show. 

 When there appears a ball within the gatherer, the leaf 

 generally proves to be one of those compound leaves, which 

 close as the evening advances. The gradation from this to 

 the .mimosa, or those leaves which move with a touch, seems 

 effected by more balls, and by the spiral wire being knotted 

 in a more complicated manner. It would have been curious 

 tp show one of each of these specimens, which l have drawn 



^ • The name by which I distinguish the increased part of the peduncle. 

 ; t See Journal, vol. XXIV, p. 160. 



for 



crs 



