150 LEAVES. 



upon the hairy border, they are unable to return, and 

 at last fall into the water, where they perish. Here 

 unquestionably they may be of use to the plant, by 

 furnishing it with nourishment, which is absorbed by 

 its hollow leaf, for the air evolved by decaying insects 

 is favourable to vegetation. Dr. Smith therefore con- 

 cludes that the design of this singular construction is 

 to entrap and retain the small insects which become 

 food for their larger companions, and nourishment for 

 the plant which contains them, and he thinks it curious, 

 M that an European insect should find out an American 

 plant in a hothouse, in order to fulfil that purpose."* 



It would be useless to find fault with this hypothesis, 

 ©r to mention others which have been defended with 

 equal ingenuity, for none of them rest on the substantial 

 basis of observation and experiment. It remains to 

 be ascertained, whether the water which the leaf con- 

 tains is derived from its root or from another source, 

 whether it is pure, or impregnated with any of the veg- 

 etable secretions, whether the insects with which it is 

 stored, are forced into its cavity or become victims to 

 their own temerity, whether they furnish birds and in- 

 sects with food, and whether the plant is less vigorous, 

 when all foreign substances are excluded from the cav- 

 ity of its singular leaves. When these questions are all 

 answered, there will be time enough to speculate ; but 

 until the subject is more thoroughly investigated, no 

 theory can rest on a substantial foundation. 



The leaf of the Nepenthes distillatoria, Fig. 55, a plant 

 that grows among the bogs of India, presents a similar 

 anomaly. A pitcher-shaped appendage attached to its 

 superior extremity is partially filled with water, but the 



* Smith's Introduction. 



