52 



MORPHOLOGY OF LEAVES. 



[LESSON 7. 



126. 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 Dionam or Venus's Fly- 

 trap, which grows in the sandy bogs 

 around Wilmington, North Carolina. 

 Here (Fig. 81) each leaf bears at its 

 summit an appendage which opens and 

 shuts, in shape something like a steel- 

 trap, and operating much like one. For 

 when open, as it commonly is when the 

 sun shines, no sooner does a fly alight 

 on its surface, and brush against any 

 one of the several long bristles that grow 

 there, than the trap suddenly closes, 

 often capturing the intruder, pressing it 

 all the harder for its struggles, and com- 

 monly depriving it of life. 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 minute glands of the inner sur- 

 face, and is apparently digested ! How such 

 and various other movements are made by 

 plants, some as quick as in this case, 

 others very slow, but equally wonderful, 

 must be considered in a future Lesson. 



127. kaves serving both Ordinary and 



Special Purposes, Let us now remark, that 

 the same leaf frequently answers its gen- 

 eral purpose, as foliage, and some special 

 purpose besides. For example, in the Dio- 

 nasa, the lower part of the leaf, and prob- 

 ably the whole of it, acts as foliage, while the 

 appendage serves its mysterious purpose 

 as a fly-catcher. In the Pea and Vetch 

 (Fig. 20, 127), the lower part of the leaf 

 is foliage, the upper a tendril. In the Pitcher-plants of the Indian 

 Archipelago (Nepenthes, Fig. 80) which are not rare in conserva- 

 tories, the lower part of the leaf is expanded and acts as foliage ; 



FIG. 80. Leaf of Nepenthes: leaf, tendril, and pitcher combined. 



FIG. 81. Leaves of Dionaea : the trap in one of them open, in the others closed. 



