84 PLANT PHYSIOLOOY 



independently, present. They are not more intimately as- 

 sociated with the higher organism. 



The same hypothesis has been extended to the digestion 

 which takes place in the pitcher-like leaves of Nepenthes, and 

 with much more justice to the decompositions in the similar 

 leaves of Sarracenia. For Nepenthes, Goebel* and Vinest 

 have proved the presence in the pitchers of an enzym capa- 

 ble of digesting proteid matters. Goebel J says that the 

 Sarracenias and Darhngtonia secrete neither an enzym nor 

 a substance which checks decay ; that is, they do not them- 

 selves digest the bodies of insects, but, on the other hand, 

 they do not prevent the decomposition of these by living 

 organisms contained in the pitchers. The Sarracenias and 

 Darhngtonia, like Drosera, inhabit northern bogs, the soils 

 of which are relatively poor in nitrogen. The leaves are 

 large, erect or inclined, pitcher-shaped, holding often con- 

 siderable volumes of water. Owing to the peculiar form, the 

 slipper^' inner surface, and its downward-pointing hairs, the 

 mouth of a pitcher is an alighting-place as uncertain as it 

 is natural for flying insects. They fall down into the pitch- 

 er; their escape is prevented by the shape, slippery sur- 

 face, and hairiness of the inside of the pitcher ; finally they 

 die, either by drowning, or of starvation and exhaustion 

 from their futile efforts to get out. They now decay, bac- 

 teria feeding upon their dead bodies liberating soluble or- 

 ganic nitrogen compounds which are absorbed through the 

 walls of the pitchers. li Goebel's conclusions, based on 

 investigations carried on in the Botanic Garden at Marburg, 

 are confirmed by equally reliable investigations of these 

 plants in their native homes, they may constitute an inter- 

 esting case of an association mutually beneficial; but it 

 seems hardly a sufiicient reason for the formation of such 

 extremely modified leaves as these pitchers, that they 

 serve only as traps for insects, culture-tubes for bacteria, 



* Goebel. K. Pflanzenbiologische Schildeningen, 2ter Theil, p. 186 et 

 seq. 



f Vines, S. H. The proteolytic enzyme of Nepenthes. Annals of Botany, 

 Vol. XI., 1897. Vol. XII., 1898. 



} Goebel, K. L. ,. p. 170. 



