348 ASSIMILATION. 



" The cause which attracts flies is evidently a viscid substance, 

 resembling honey, secreted by or exuding from the internal sur- 

 face of the tube. From the margin where it commences, it does 

 not extend lower than one fourth of an inch. The falling of the 

 insect as soon as it enters the tube is wholly attributable to the 

 downward or inverted position of the hairs of the internal surface 

 of the leaf. At tne bottom of the tube, split open, the hairs are 

 plainly discernible, pointing downwards ; as the eye ranges up- 

 ward they gradually become shorter and attenuated, till at or 

 just below the surface covered with the bait, they are no longer 

 perceptible to the naked eye nor to the most delicate touch. It 

 is here that the fly cannot take a hold sufficiently strong to sup- 

 port itself, but falls." 



914. The tissues of the internal surfaces of the pitchers have 

 been classified by Hooker in the following manner : 



" (1) An attractive surface, occupying the inner surface of 

 the lid, which possesses stomata, and (in common with the 

 mouth of the pitcher) minute honey-secreting glands ; it is, 

 further, often more highly colored than any other part of the 

 pitcher, in order to attract insects to the honey. 



" (2) A conducting surface, which is opaque, formed of 

 glassy cells, which are produced into deflexed, short, conical 

 processes. These processes, overlapping like the tiles of a 

 house, form a surface down which an insect slips, and affords 

 no foothold to one attempting to crawl up again. 



" (3) A glandular surface (seen in S. purpurea), which occu- 

 pies a considerable portion of the cavity of the pitcher below the 

 conducting surface. It is formed of a layer of epidermis with 

 sinuous cells, and is studded with glands. Being smooth and 

 polished, this, too, affords no foothold for escaping insects. 



" (4) A detentive surface, which occupies the lower part of the 

 pitcher, in some cases for nearly its whole length. It possesses 

 no cuticle, and is studded with deflexed, rigid, glass-like, needle- 

 formed hairs, which further converge towards the axis of the 

 diminishing cavity ; so that an insect, if once amongst them, is 

 effectually detained, and its struggles have no other result than 

 to wedge it lower and more firmly in the pitcher." 



915. Mellichamp describes a line of saccharine liquid which 

 leads up from the base of the leaf to its brim. This secretion 

 comes from glands at the mouth of the pitcher ; but it is found 

 only at certain periods. Led by this lure, insects are drawn 

 towards the brim of the pitcher, and sooner or later they are 

 caught in considerable numbers in the pitchers themselves. 



