I.] SLEEP OF FLOWERS 25 



t 



tions with insects, is the habit of " sleeping," which 

 characterises certain species. 



Many flowers close their petals during rain, which 

 is obviously an advantage, since it prevents the honey 

 and pollen from being spoilt or washed away. Every- 

 body, however, has observed that even in fine weather 

 certain flowers close at particular hours. This habit 

 of going to sleep is surely very curious. Why should 

 flowers do so ? 



In animals we can understand it ; they are tired 

 and require rest. But why should flowers sleep ? 

 Why should some flowers do so, and not others ? 

 Moreover, different flowers keep different hours. The 

 Daisy opens at sunrise and closes at sunset, whence 

 its name " day's-eye." The Dandelion (Leontodon 

 taraxacum) is said to open about seven and close 

 about five ; Arenaria rubra to be open from nine to 

 three ; 1 Nymphcza alba from about seven to four ; the 

 common Mouse-ear Hawkweed (Hieracium Piloselld) 

 from eight to three ; the Scarlet Pimpernel (Ana- 

 gallis arvensis) to waken at seven and close soon 

 after two ; Tragopogon pratensis to open at four in 

 the morning, and close just before twelve, whence 

 its English name, "John go to bed at noon." Far- 

 mers' boys in some parts are said to regulate their 

 dinner-time by it. Other flowers, on the contrary, 

 open in the evening. 1 



Now, it is obvious that flowers which are fertilised 

 by night-flying insects would derive no advantage from 



1 In my own observations the opening and closing was more gradual 

 and more dependent on the weather than I should have expected from 

 the statements quoted above. 



