ETIOLA TED LEA YES 



193 



sition. U])()n the outer portion of the ])itc'her a Hue of ghiiiduhir tissue 

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

 tion, which so changes its nature toward the toj) 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 prom])tly occurring by means of 

 enzymes excreted into the liquid by special glands located upon the 

 inner face of the i)itchcr. 



Fig. 560. Modifitd (pitcher) leaf of NepeiUhcs. 561. Modified leaf of Die 



The Venus' s Fhj-fntp. — Another form is the well-known ^'enus's 

 fly-trap (Fig. 5()1), which secretes a nectar by certain glands which 

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

 seized through the sjiasmodic 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 i)lace. That the 

 nutrients thus absorbed are of service to the ])lant has been proved by 

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

 estimated by comparing their re})roduction with that of other similar 

 plants, similarly treated in all respects except that they were dei)ri\ed 

 of this form of food. 



Etiolated Leaves. — In other cases, the ])lant being nourished by 

 means of fully prepared nutrients absorbed from other leafy plants 

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

 phyll tissue uj)()n which their ordinary functions (lei)cnd, and arc 

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

 in form. 

 13 



