208 



BOTANY OF THE LIVING PLANT 



dependent upon the absorption of nitrogenous matter from the 

 stimulating body : a piece of indigestible matter produces less secre- 

 tion and without proteolytic powers. The body of the insect, or the 

 cube of white-of-egg, enveloped in the secretion, is slowly digested, 

 and the dissolved material, together with the secretion itself, absorbed 

 into the cells of the leaf. In the white-of-egg the rounding of the 

 edges of the cube can easily be followed. All that remains of an 

 insect when digestion is complete are the insoluble chitinous parts. 

 The process of digestion in the Butterwort, and Venus' Fly Trap is 

 essentially the same as in Sundew. The difference lies in the varying 

 perfection of the mechanism. 



FIG. 157- 



Leaves of Drosera rotundifolia : enlarged. A, in the receptive state before 

 stimulation. B, after stimulation, viewed from above, with tentacles partly 

 incurved. (After Darwin.) 



In Nepenthes the peculiarly formed leaves are an effective trap for 

 luring small animals into the fluid that partly fills the pendent urn 

 (Fig. 1 58). In Botanic Gardens these are often choked by the partially 

 digested remains of ants, cockroaches, and other victims. There is 

 no motile mechanism that catches them, but only a static trap. The 

 lip of the urn slopes inwards, and is cartilaginous and smooth, with 

 secreting glands at its inner rim. Insects attracted by the secretion 

 into a dangerous position on the smooth sloping surface lose their 

 footing, and fall into the urn, from which, owing to the absence of 

 foothold on the converging walls, there is no escape. Death and 

 digestion follow. 



The secretion within the urn is exuded by numerous large, button- 

 shaped glands upon its inner surface. Each is covered on its upper 





