SLEEP OF PLANTS. 245 



noon. This is one of the best plants to obtain for 

 persons who reside in town, and desire to watch the 

 movements of the leaves. It will grow freely and 

 readily in a small flower-pot, by the window, in a 

 sitting room, covering the top with its delicate green 

 leaves, so as to be a pretty object, as well as a most 

 interesting one. Several other species are commonly 

 cultivated, and many of these exhibit similar pheno-; 

 mena, although some of them do not. 



The blimbing (Averrhoa bilimbi) is an oriental 

 fruit tree, which may be mentioned here because of 

 its belonging to the same natural order as the humble 

 little wood-sorrel. This tree and some of its move- 

 ments were known a hundred years ago. 1 The leaves 

 move spontaneously during the day, they move also in 

 response to a touch, being what is termed " sensitive," 

 and finally they subside into a condition of sleep at 

 night. It is said to be a remarkable sight to observe 

 the leaflets of this tree sinking rapidly one after the 

 other, and then slowly rising. At night the leaflets 

 hang down vertically, and are then motionless. By 

 regulating the light in a conservatory, the behaviour 

 of a plant under variations of light was observed. A 

 leaflet was seen to rise in diffused light for twenty- 

 five minutes, and then a blind was removed so that a 

 strong light fell upon it, and within a minute the 



Dr. Bruce in " Philosophical Transactions for 1785," p. 356. 



