THE LIBRARY. 75 



that it is not known in any determinate manner why the 

 name has been given to what is called The sleep of plants 

 (The Somniis Plantarum of Linaeus), and what difference of 

 constitution occasions this phenomenon so pronounced in 

 some, and imperceptible or awanting in others. When 

 the sun declines below the horizon, and the long twilight 

 comes on, it may be observed that the leaves of certain 

 species of plants, as those of the Cassia floribunda, 

 turn their leaflets in such a way that they approximate 

 one another considerably, a movement which is generally 

 manifested by the acacias, which are extensively cultivated 

 in our gardens as an ornamental tiee: And who has not 

 heard of the sensitive plant, Mimosa pudica L., whose move- 

 ments, like the natural and periodic ones of sleep, are 

 originated so easily by a passing cloud obscuring for a time 

 the light of the sun, or the distant galloping of a horse, or 

 by the excitation which an insect produces by alighting on 

 the leaves ? Who is not aware that it is enough to touch 

 the extremity of one of its leaflets, in order that all the 

 leaves, and even a b.anch, close up as if frightened by the 

 imprudent mortal who has taken the libeity to come near 

 it? 



' Remarkable also are the movements of the Htdysarum 

 girans L. (Desmodium girans D.G.), a curious plant, discovered 

 in Bengal by Lady Monsen, in which a large odd 

 leaflet is in constant motion ; and the other two, a good 

 deal less in size, keep up a lively oscillation of a peculiar 

 kind, on which the vertex, or extremity, of each describes 

 an elipsis the plane of which is oblique to the axis of the 

 leaf. And we may lastly cite the Dionaii Muscipula L. 

 (the Venus Trap-fly), which, togetherwith the Drosera.to the 

 Saracenia, and the Altpanthus, has by its movements given rise 

 to a lengthened controversy, in which Darwin, Hooker, 

 Reess, and Will, have displayed their genius and vast 

 experience, as they have discussed with all earnestness the 

 fact whether they be carnivorous plants or not. 



' In 1866, Ligeisan and Divers having made curious 

 experiments on the sensitive plant, found a remarkable 



