On the Leaves of the Sensitive Plant. 77 



say and Dr. Dutrochet. Mr. Lindsay's observations are to be 

 met with in a MS. preserved in the hbrary of the Royal 

 Society, which is dated July 1790 : this essay is alluded to by 

 Dr. Smith in his ♦* Introduction to Botany." Dr. Dutrochet's 

 experiments were published in his " Recherches anatomiques 

 et physiologiques sur la Structure intime des Animaux et des 

 Vegetaux," which appeared in 1824. With the latter author 

 the reputation of originality is likely to rest : not undeservedly, 

 indeed, as there is no reason to suppose that his experiments 

 were suggested by a knowledge of those performed by Lindsay. 

 It is, however, an act of literary justice to secure to Mr. Lindsay 

 the credit of undoubted priority in describing the phenomena 

 which he noticed in common with Dutrochet. I have drawn 

 up the following remarks partly for this purpose — partly to have 

 an opportunity of mentioning some circumstances which escaped 

 the observation of both experimentalists. 



The leaves of the Mimosa Pudica consist either of one or 

 two or three pairs of leaflets, and occasionally terminate by an 

 odd one. Each leaflet bears from twenty to sixty subleaflets, 

 which are disposed in pairs. The petiole or stalk of each leaf, 

 at the extremity which is attached to the branch or stem of the 

 peant, swells into an intumescence varying from three to five 

 in length. A similar intumescence, of proportionate dimen- 

 sions, is seen upon each subpetiole, where it is articulated with 

 the petiole, and upon the base of the stalk of each subleaflet ; 

 the intumescence is the part in which motion takes place. 



During the day-time the petioles are obseiTed to have a 

 direction upwards, or rather to form an acute angle with the 

 upper part of the stem or branch, to which they are attached : 

 the subpetioles are divergent : the subleaflets are spread out, so 

 as to lie nearly in one plane. {Fig. 1.) 



During the night the petioles are found to be depressed ; 

 the subpetioles to be drawn together, the subleaflets folded, 

 the upper or solar surfaces of each pair being brought into 

 contact. {Fig, 2.) 



The leaves rise, the leaflets diverge, and open by throwing 

 down their subleaflets, at daybreak : the opposite changes occur 

 about sunset. The experiments that are to be described, are 

 supposed to be performed in the day-time.. 



