154 THE BEAUTIES OF NATURE CHAP. 
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 disadvantage, because it would render 
them liable to be robbed of their honey and 
pollen, by insects which are not capable of 
fertilising them. I have ventured to suggest 
then that the closing of flowers may have 
reference to the habits of msects, and is may 
be observed also in support of this, that wind- 
fertilised flowers do not sleep; and that many 
of those flowers which attract insects by 
smell, open and emit their scent at particular 
hours; thus Hesperis matronalis and Lychnis 
vespertina smell in the evening, and Orchis - 
bifolia is particularly sweet at night. 
But it is not the flowers only which 
“sleep” at night; in many species the leaves 
also change their position, and Darwin has 
given strong reasons for considering that the 
object is to check transpiration and thus tend 
to a protection against cold. 
