ETIOLATED LEAVES 



193 



sition. Upon the outer portion of the pitcher a line of glandular tissue 

 stretches downward. The insect feeds upward along this line of secre- 

 tion, which so changes its nature toward the top of the pitcher, that 

 by the time the insect reaches that point he is more or less intoxi- 

 cated, and on crossing the margin, or quickly thereafter, falls into the 

 liquid and is drowned, digestion promptly occurring by means of 

 enzymes excreted into the liquid by special glands located upon the 

 inner face of the pitcher. 



Fig. 560. Modified (pitcher) leaf of Nepenthes. 561. Modified leaf of Dionaea 



The Venus's Fly-trap. — Another form is the well-known Venus's 

 fly-trap (Fig. 561), which secretes a nectar by certain glands which 

 surround its margin. The insect, alighting upon this point, is instantly 

 seized through the spasmodic coming together of the two lateral halves 

 of the leaf, which act precisely like the jaws of a trap. Digestive fluids 

 are then immediately poured forth from special glandular tissues on 

 the leaf-surface and digestion and absorption take place. That the 

 nutrients thus absorbed are of service to the plant has been proved by 

 elaborate experiments, in which the effects of such feeding have been 

 estimated by comparing their reproduction with that of other similar 

 plants, similarly treated in all respects except that they were deprived 

 of this form of food. 



Etiolated Leaves. — In other cases, the plant being nourished by 

 means of fully prepared nutrients absorbed from other leafy plants 

 (host-plants) upon which they are parasitic, the leaves lose the chloro- 

 phyll tissue upon which their ordinary functions depend, and are 

 known as Etiolated leaves. They become reduced in size and scale-like 

 in form. 

 13 



