6 FLOWERS FERTILISED BY INSECTS. [CHAP. 



effectually prevents the unfortunate victim from 

 getting out again. 



I will only allude to one foreign case, that of the 

 Sarracenia. 1 In this genus some of the leaves are in 

 the form of a pitcher. They secrete a fluid, and are 

 lined internally with hairs pointing downwards. Up the 

 outside of the pitcher there is a line of honey glands 

 which lure the insects to their destruction. Flies 

 and other insects which fall into this pitcher cannot 

 get out again, and are actually digested by the plant. 

 Bees, however, are said to be scarcely ever caught. 



Every one knows how important flojers_are_a 

 insects.; every one knows that bees, butterflies, etc., 

 derive the main part of their nourishment from the 

 honey or pollen of flowers, but comparatively few are 

 aware, on the other hand, how much the flowers them- 

 selves are dependent on insects. Yet it has, I think, 

 been clearly shown that if insects have been in some 

 respects modified and adapted with a view to the 

 acquirement of honey and pollen, flowers, on the other 

 hand, owe their scent and honey, their form and 

 colour, to the agency of insects. Thus the lines and 

 bands by which so many flowers are ornamented have 

 reference to the position of the honey ; and it may be 

 observed that these honey-guides are absent in night 

 flowers, where they of course would not show, and 

 would therefore be useless, as for instance in Lychnis 

 vespertina or Silene nutans. Night flowers, moreover, 

 are generally pale ; for instance, Lychnis vespertina is 

 white, while Lychnis diurna t which flowers by day, 

 is red. 



See Hooker, British Association Journal, 1874. 



