III. 



PLANT SLEEP. 



W wonderful and beau- 

 tiful is the arrange- 

 ment by wbicli plants 

 obtain the rest that 

 with them, as with all 

 beings and things that 

 grotv, is essential to 

 their well-being in the 

 wise economy of Nature ! 

 We do not here allude to the really curious and 

 interesting arrangements by which leaves during 

 the night in Summer alter their position, and, so 

 to speak, fold themselves np to sleep. Familiar 

 examples of this singular function are afforded in 

 the case of the pretty Wood Sorrel {Oxalis 

 acetosella), which folds its upper surfaces, that 

 most require protection, together during the 

 night, and unfolds them again in the morning; 



