I INTRODUCTION 1 1 



relations 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 ? More- 

 over, some flowers sleep and not others, and those which 

 do sleep keep difi"erent hours. The Daisy opens at sun- 

 rise and closes at sunset, whence its name " day's-eye." 

 The Dandelion [Taraxacum officinale) is said to open 

 about seven and close about five ; Arenaria rubra, 

 to be open from nine to three ; Nymphoia alba, from 

 about seven to four ; the common Mouse-ear Hawkweed 

 [Hieraciuin Pilosella), from eight to three ; the Scarlet 

 Pimpernel (Anagallis 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." Farmers' 

 boys in some parts are said to regulate their dinner- 

 time by it. Other flowers, on the contrary, open in the 

 evening.^ 



Now, it is obvious that flowers which are fertilised 

 by night-flying insects would derive no advantage from 

 being open by day ; and, on the other hand, that those 

 which are fertilised by bees would gain nothing by being 

 open at night. Nay, it would be a distinct disadvan- 

 tage, because it would render them liable to be robbed 

 of their honey and pollen by insects which are not 

 capable of fertilising them. It may be observed also 

 that wind-fertilised flowers do not sleep ; and that some 

 of those flowers which attract insects by smell emit 



^ In my own observations the opening and closing were more gradual and 

 more dependent on the weather than I should have expected from the state- 

 ments quoted above. 



