22 HOW PLANTS USE ANIMALS. 



petioles which loiui, at their extremities, pitchers surmounted 

 by a hinged lid. Inside the pitchers is secreted a watery, slight- 

 ly acid fluid, partly tilling the cavities. Upon the lips of the 

 pitchers, as in the case of the Sarracenia, is produced a sweetish 

 substance exceedingly attractive to winged insects which, falling 

 into the fluid within, are soon dissolved by it, and their sub- 

 stance absorbed by the plant for its nourishment. Dr. Hooker 

 found that although the fluid within the pitcher of Nepenthes 

 possesses extraordinary power of digestion, yet when removed 

 from the pitchers, before they have been excited, and placed in 

 a vessel, it has no such power, altliough it is already acid. Dar- 

 win acc(nints for this fact by the supposition that the proper 

 ferment is not secreted until some exciting matter is absorbed.* 

 Order III. — The Droseraceae is a large fanjily of very re- 

 markable plants, distributed throughout the world; and fre- 

 quently abounding in bogs and marshy localities. It emliraces 

 six genera and about one hundred and ten species one hundred 

 of these belonging to a single genus, Drosera. Owing to its 

 adaptation for entrapping insects, the family has attracted a 

 large share of attention, and several of its members have been 

 subjected to numberless experiments. 



1. In some respects the niost wonderful species is the Venus' 

 fly-trap (Dionaea muscipuhi), '^o named from the extreme irrita- 

 bility of its leaves, which quickly close like a steel-trap at the 

 slightest touch. It is a native <>f the eastern part of North 

 Carolina, where it flourishes in sandy bogs along rivers from the 

 Neuse to the Santee. It adheres to the soil by one or two sniall 

 roots, terminated 1.) 3' bulbous enlargements, which probably serve 

 for the absorption of water. In conservatories it is often culti- 

 vated in a pot of bog material i)laced in a pan of water, proving 

 that it is not dependent upon the soil for its food. The stem is 

 from six to twelve inc^hes high, and bears an umbel of eight to ten 

 white flowers. Its leaves are all radical, forming a rosette, the 

 blades are roundish and two-lobed, their margins fringed with 

 long, sharp, rigid spines. The upper surface of each leaf has 



*Dar\vin. lust'ctivorous Plants, p. 97. 



