SLEEP OF PLANTS. 251 



to propose a satisfactory solution of these phenomena, 

 for in one plant we have an illustration of all the 

 three methods in which different species of lupin have 

 been observed to pass the night. 



The French bean {Phaseolus vulgaris) also ex- 

 hibits sleep movements, but only under special con- 

 ditions. With plants growing out of doors no 

 tendency to sleep was observed in July, whereas in 

 August the same plants had most of their leaflets in 

 a condition of repose. In this plant the leaflets sink 

 vertically at night, whilst the footstalk rises a little. 

 Other species of the same genus have been observed, 

 and all of them sleep in a like manner. 



We have given as many illustrations as necessary 

 from ordinary and well-known plants, either native, 

 or in common cultivation, and these we would now 

 supplement by a few observations on foreign plants 

 such as are cultivated in the green-house or conser- 

 vatory. For the facts we shall be indebted here, as 

 on previous occasions, to Mr. Darwin's recent work, 

 which, like his other works, is a perfect cyclopaedia 

 of facts and observations. 



In Desmodium gyrans, one of the "sensitive 

 plants," so-called, the leaves consist of a large 

 elliptical terminal leaflet, and two very small lateral 

 ones. The large terminal leaflet sinks vertically 

 at night, whilst the footstalk, or petiole, rises. 

 By this rising of the petioles an altered and more 

 compact appearance is given to the plant. The 



