466 THE UNIVERSE. 



more striking form in hotter countries. Humboldt, Avhile 

 traversing the banks of the Magdalena, observed that 

 there plants awake much later than in less torrid countries, 

 as if vegetation in these climates shared in the indolence 

 which is observable in all the peoples scattered beneath the 

 equator. 



Many Howers close every evening in order to give them- 

 selves up peacefully to repose. There are some, such as 

 certain bind-weeds, which are very lazy, falling asleep long 

 before siuiset, and only rousing \ip very late each morning, 

 Avhen the sun darts his rays upon them. 



In the evening if we view a meadow in which these 

 impressible flowers abound, its mournful aspect renders it 

 unrecognizable. In full mid-day, when it is enamelled 

 with all these open corollas, it seems a mass of verdure 

 filled with great yellow and blue eyes wdiich gaze at us. 

 But when twilight arrives all these seem to have closed 

 their eyelids in order to slumber : the living aspect of the 

 meadow has vanished; all appears inanimate — its flowers 

 are sleeping. 



INIen have sought to attribute the phenomenon we are 

 speaking of to the difference between the temperatiu'e 

 of the day and the temjierature of the night; but when it 

 was seen to take place in green-houses, where the heat was 

 equal night and day, they w^ere obliged to seek for some 

 other cause. 



De CandoUe showed by some interesting experiments 

 that within the empire of Flora sleep is to be attributed to 

 the absence of light. By throwing a very liright light 

 upon sensitive plants during the night, and conversely, by 

 placing them in profound darkness during the day, the 

 learned botanist succeeded in completely changing their 

 habits. These plants closed up their leaflets and slept the 



