()4. Mr Spittal on the Mimosa pudica. 



destroyed its vitality, could cause the leaf, after this opera- 

 tion, to flex itself towards the ground. This experiment, then, 

 proves that the portion of the bourrelet which raises the leaf, is 

 not the upper half, but that it is forced up by the action of the 

 lower half alone. 



To shew the action of the upper, I removed the lower half 

 of the bourrelet in the same manner as formerly mentioned, con- 

 cerning the upper, immediately after which, the leaf bent itself 

 towards the ground, and there it remained, and never rose again, 

 although otherwise quite natural. The descent was always more ra- 

 pid after this operation than the ascent of the leaves after the re- 

 moval of the upper half of the bourrelet, as in the former ex- 

 periment ; and this no doubt is caused by the assistance which 

 gravity gives to the force downwards ; but it is manifest that 

 there is a force pushing downwards, for, on simply inverting the 

 flower-pot containing the plant carefully, the leaves operated on 

 will be found to be only sHghtly raised from the earth, the effect of 

 gravity being in such a case reversed. This experiment, then, proves 

 that the lower part of the bourrelet does not cause the descent of 

 the leaf, but that this is confined to the upper half alone, the mo- 

 tion beingcaused by incurvation downwards, as the contrary is pro- 

 duced by incurvation upwards, in consequence of the occasion- 

 al turgescence of these parts, excited by the stimuli mention- 

 ed. After these operations the leaves remained in a healthy con- 

 dition for a considerable time, generally for many days, but 

 were rendered less able to bear the heat of the mid-day sun. 



The leaves of the Mimosa pudica, like the leaves of most 

 plants, turn themselves towards the light, and this is effected in 

 theplant under consideration by the action of the bourrelet, which 

 possesses a lateral incurvation to a slight extent ; and in remov- 

 ing the upper or under portions of the bourrelet, in the experi- 

 ments described, if the incision happened to be a little to either 

 side, the leaves were invariably twisted upwards or downwards, 

 and to one or other side of the stem. 



Such, then, are i-epetitions of a few of the experiments of M. 

 Dutrochet, on this very interesting plant, and the conclusions to 

 which they lead are quite in unison with those of the author 

 himself. There are many more however, just as interesting, 

 which at some future opportunity I propose to consider. 



