SECTION 7.] 



SPECIAL LEAVES. 



65 



172. The leaf of Nepenthes (Fig. 175) combines three structures and 

 uses. The expanded part below is foliage : this tapers into a tendril for 



174 175 



climbing ; and this bears a pitcher with a lid. Insects are caught, and per- 

 haps digested, in the pitcher. 



173. Leaves as Fly-traps. Insects are 

 caught in another way, and more expertly, 

 by the most extraordinary of all the plants 

 of this country, the Diouaea or Venus's Fly- 

 trap, which grows in the sandy bogs around 

 Wilmington, North Carolina. Here (Fig. 

 176") each leaf bears at-its summit an appen- 

 dage which opens and shuts, in shape some- 

 thing like a steel-trap, and operating much 

 like one. For when open, no sooner does 

 a fly alight on its surface, and brush against 

 any one of the two or three bristles that grow 

 there, than the trap suddenly closes, captur- 

 ing the intruder. If the fly escapes, the trap 

 soon slowly opens, and is ready for another 

 capture. When retained, the insect is after 

 a time moistened by a secretion from mi- 

 nute glands of the inner surface, and is 

 digested. In the various species of Drosera or Sundew, insects are caught 



Fin. 174. Leaf of Sarracenia purpurea, entire, and another with the upper part 



off. 



FIG. 175. Leaf of Nepenthes; foliage, tendril, and pitcher combined. 



FIG. 176. Leaves of Dionaea; the trap in one of them open, in the others closed. 



