LECT. XI.J CAULINAR AND FOLIAR APPENDAGES. 679 



the air is charged with moisture, the scroll swells, 

 and by unrolling itself enlarges the thickness of 

 the ring, and thus produces a pressure upwards 

 and backwards, by which the lid is forced open. 

 I have found, from experiment, that the en- 

 largement of the ring one sixteenth of an 

 inch, would bring the lid nearly into the erect 

 position ; and it is evident that the opening of 

 the lid must follow such an enlargement of the 

 ring, unless we suppose that the hinge length- 

 ens synchronously with the unrolling of the scroll, 

 which is not probable. In advancing this explana- 

 tion, I must allow that it is purely hypothetical, 

 and requires to be confirmed by observations on 

 the habits of the plant in its living state. 



With regard to the fluid found in these vege- 

 table pitchers, the most probable opinion is, that 

 it is obtained from the atmosphere, and is intended 

 for the nourishment of the plant; for we can 

 scarcely suppose that so large a quantity of mois- 

 ture can be thrown out as a excretion, in a plant 

 growing in the dry, sterile situations where Ne- 

 penthes is found, and for the sole purpose of drown- 

 ing a few insects*. Rumphius indeed observes, that 

 the insects which crawl into the pitcher all die, 



* Sir E. J. Smith supposes these pitchers to be merely fly- 

 traps; and, speaking of the source of the fluid, says it is 

 " certainly secreted through the footstalk of the leaf." Introd. 

 to Phys. and Syst. Bot, p. 197. 



x x 4 



