218 Elementary Biology. 



would otherwise soon fill the hollow portion of the leaf and 

 render it useless. The microscopic structure of the trumpet 

 is of some importance. The lid and the mouth of the tube 

 are covered by honey glands, and by small downwardly 

 directed hairs. Some of these glands are also distributed 

 on the outside of the trumpet on the ladder-like ledge which 

 runs up one side. Following upon the gland-bearing area 

 is a zone covered by slippery epidermal cells ; after that a 

 zone on which are numerous glands secreting the fluid with 

 which the trumpet is partly filled. Lastly, there comes a 

 zone where the epidermal cells are pulled out into long, 

 stiff downwardly directed hairs or bristles. An insect, lured 

 up the honey-strewn path on the outside of the pitcher in 

 search of more honey, climbs into the mouth itself, and, 

 gently goaded by the short hairs of that region, reaches the 

 glassy epidermis over which it slides rapidly downwards 

 amongst the secretory glands, only to be stranded on the 

 long bristles, which, though they permit of a downward, effec- 

 tually prevent an upward, movement. Indeed, the struggle 

 of the hapless visitor only serves to stimulate the glands to 

 more active secretion, washing it into the putrid fluid below. 



Virgil's lines 



Facilis descensus Averno ; 



Seel revocare graclum superasque evadere ad auras, 

 Hoc opus, hie labor est 



are not more applicable to the descent into Avernus than 

 they are to trumpet-shaped leaves of Sarracenia. 



The leaf seems to have the power only of absorbing the 

 gases arising from the decomposition of the dead bodies and 

 decaying animal matter lying in the pitcher. 



The description of these two species must suffice to illus- 

 trate this subject. Full details of the marvellous adaptations 

 for the absorption of nitrogenous organic compounds occur- 

 ring in other species and genera will be found in the article 

 on * Insectivorous Plants ' in the Encyclopedia Britannica 

 or in Darwin's Insectivorous Plants. 



