i] . INSECTIVOROUS PLANTS. 5 



ivorous plant. In the genus Pinguicuk, which frequents 

 moist places, generally on mountains, the leaves are 

 concave with incurved margins, and the upper surfaces 

 are covered with two sets of glandular hairs. In this 

 case the naturally incurved edges curve over still more 

 if a fly or other insect be placed on the leaf. 



Another case is that of Utricularia, an aquatic species, 

 which bears a number of utricles or sacs, which have 

 been supposed to act as floats. Branches, however, 

 which bear no bladder float just as well as the others, 

 and there seems no doubt that their real use is to 

 capture small aquatic animals, which they do in con- 

 siderable numbers. The bladders in fact are on the 

 principle of an eel-trap, having an entrance closed with 

 a flap which peimits an easy entrance, but 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 flowers are to in- 

 sects ; every one knows that bees, butterflies, &c, 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 themselves are 

 dependent on insects. Yet it has, I think, been clearly 

 1 See Hooker, British Association Journal, 1874. 



