SOME PLANTS WHICH ENTRAP INSECTS. 



423 



aboul in the Alps. The leaves are broad and undivided, slightly in- 

 rolled at the edges and coaled on the upper surface with a sticky .slime 

 exuded from minute groups of glandular cells. An insect alighting 

 on the leaf is can-lit and held by the sticky secretion, and the more 

 it struggles to escape the more firmly is it held and the more com- 

 pletely does its whole body become involved. If the insect has chanced 

 to alight near the edge of the leaf the inrolled margin will roll still 



Fig. 6. Flower of the Parrot's-beak Pitcher-plant. 



further so as to cover it completely, but whether near the edge or not, 

 there is something in the contact of this available food which causes 

 the excretion of juice to be so abundantly renewed as to be sure to 

 envelop the insect. In the renewed excretion there is to be found a 

 digestive princi le such as occurs in the pitchers of the East Indian 

 pitcher-plant, so the captured prey, soon smothered to death, is also 

 rapidly consumed and its essence carried into the leaves by means of 

 the glandular secreting cells. 



It is of interest that the only case in which any of the insectivorous 

 plants have been found of practical use is in connection with the 

 presence of the digestive juice in the butterwort. There is associated 



