294 INDIRECT BENEFITS DERIVED FROM INSECTS. 



as in Sarraccfiia, Nepenthes, Aquarium, Cephalotus, &c., 

 the tubular leaves of which are usually found stored with 

 putrefying insects. In this last class may be placed the 

 common Dipsacus of this country, the connate leaves of 

 which form a kind of basin round the stem, that retains 

 rain-water in which many insects are drowned. To these 

 a fourth class might be added, consisting of those plants 

 whose flowers smelling like carrion [Stapelia hirsuta, &c.) 

 entice flies to lay their eggs upon them, which thus 

 perish. 



The number of insects thus destroyed is prodigious. 

 It is scarcely possible to find a flower of the Muscicapce 

 Asclcpiadecs that has not entrapped its victim, and some 

 of them in the United States closely cover hundreds of 

 acres together. 



What may be the precise use of this faculty is not so 

 apparent. Dr. Barton doubts whether the flowers that 

 catch insects, being only temporary organs, can derive 

 any nutriment from them ; and he does not think it pro- 

 bable that the leaves of Dioncca, &c., which are usually 

 found in rich boggy soil, can have any need of additional 

 stimulus. As nothing however is made in vain, there can 

 be little doubt that these ensnared insects are subservient 

 to some important purpose in the economy of the plants 

 which are endowed with the faculty of taking them, 

 though we may be ignorant what that purpose is ; and 

 an experiment of Mr. Knight's, nurseryman in King's 

 Road, London, seems to prove that in the case of Dionaca, 

 at least, the very end in view, contrary to Di*. Barton's 

 supposition, is the supplying the leaves with animal ma- 

 nure ; for he found that a plant upon whose leaves he laid 

 fine filaments of raw beef, was much more luxuriant in 



