274 THE BIOLOGY OF FLOWERING PLANTS 



constantly to be found a community of small plants and 

 animals. Oye (1921) investigated the flora and fauna of 

 terrestrial pitchers and found representatives of the fol- 

 lowing groups : M50iophycese, Desmidiaceae, Diatomaceas, 

 Rhizopoda, Nematoda, Acarina, Poduridae, Diptera, and 

 larvae of Diptera and Lepidoptera. These organisms must 

 be protected in some w^ay, probably by anti-enzymes, 

 against the action of the digestive enzymes (Hepburn and 

 Jones, 1919). 



(c) The Sarraceniacese are marsh plants of tropical and 

 sub-tropical America. Their leaves are arranged in a 

 rosette, the mature leaves having the form of pitchers, 

 standing upright, inclined outwards, or lying almost hori- 

 zontal. In Nepenthes the pitcher is part of the leaf ; in 

 Sarracenia the whole leaf except the short stalk is modified. 

 The pitcher is asymmetrical ; along the inner edge — that 

 towards the centre of the rosette — is developed a more or 

 less strongly marked wing, which increases the assimilating 

 surface. The outer side of the rim is prolonged, in Sar- 

 racenia, into an arched lid which partially protects the 

 mouth. In DarUngtonia the upper part of the pitcher is 

 completely arched over the mouth which opens downwards, 

 flanked at each side by a wide wing. In the third genus, 

 Heliamphora, the mouth is widely splayed open, and the 

 lid is rudimentary. 



The edge of the pitcher, in Sarracenia psittacina for ex- 

 ample, is furnished with a stiff rim rolled outwards. About 

 the rim, the Ud, and even the outer surface of the pitcher 

 nectar glands secrete drops of sweetish fluid. In Sarracenia 

 variolaris and Sarracenia rubra so strong is the secretion 

 that the rim appears as if smeared with syrup. Insects 

 seeking nectar are thus led towards the inside of the pitcher. 

 Below this region the inner surface of the pitcher is provided 

 with a slipping zone of quite different structure from that 

 of Nepenthes. The smooth cuticularised epidermal cells 

 have their lower edges projecting over the cells next below ; 

 the appearance is that of a tiled roof. Then comes a zone 

 which bears long bristles, also pointing downwards. Nectar 



