344 SPONTANEOUS MOVEMENTS IN PLANTS. 



656. Movements from Irritation, The leaflets of numerous Legu- 

 minous plants, especially of the Mimosa tribe, when roughly 

 touched, assume their peculiar nocturnal position by a visible and 

 sometimes a rapid movement. The Sensitive Plant of the gardens 

 (Mimosa pudica) is a familiar instance of the kind : but it does not 

 greatly exceed the Mimosa strigillosa and the Schrankia of the 

 Southern States, where the leaflets promptly fold up when brushed 

 with the hand. The most remarkable instance of the kind, how- 

 ever, is presented by another native plant of the United States, the 

 Dionsea muscipula, or Venus's Fly-trap (Fig. 228) ; in which the 

 touch even of an insect, alighting upon the upper surface of the 

 outspread lamina, causes its sides to close suddenly, the strong 

 bristles of the marginal fringe crossing each other like the teeth of 

 a steel-trap, and the two surfaces pressing together with consid- 

 erable force, so as to retain, if not to destroy, the intruder, whose 

 struggles only increase the pressure which this animated trap 

 exerts. This most extraordinary plant grows abundantly in the 

 damp sandy savannas in the neighbourhood of the Cape Fear 

 River, especially from Wilmington to Fayetteville, North Car- 

 olina, where it is exceedingly abundant ; but it is not elsewhere 

 found. 



657. A familiar, although less striking, instance of the same kind 

 is seen in the stamens of the common Barberry, which are so ex- 

 citable, that the filament approaches the pistil with a sudden jerk, 

 when touched with a point, or brushed by an insect, near the base 

 on the inner side. The object of this motion seems plainly to be 

 the dislodgement of the pollen from the cells of the anther, and its 

 projection upon the stigma. But in the Dionsea it is difficult to 

 conceive what end is subserved as to the plant by the capture of 

 insects. 



658. In a species of Stylidium of New Holland, not uncommon 

 in conservatories, the column, consisting of the united stamens and 

 styles, is bent over to one side of the corolla ; but if slightly irritated, 

 it instantly springs over to the opposite side of the flower. Some 

 other movements, which have been likened to these, are entirely 

 mechanical in their nature ; as that of Kalmia, or Sheep Laurel, 

 where the ten anthers are in the bud received into as many pouches 

 of the monopetalous corolla, and being retained by a glutinous ex- 

 udation, are carried outwards and downwards when the corolla 

 expands. In this way the slender filaments are strongly recurved, 



