276 THE BIOLOGY OF FLOWERING PLANTS 



they filled they would be mechanically incapable of re- 

 maining erect. 



The way in which the insect food is made available for 

 absorption is a matter that has not as yet been satisfactorily 

 cleared up. It has generally been supposed that no diges- 

 tive enzymes are secreted. Recently, however, Hepburn 

 (1920) claims to have demonstrated the presence of a prote- 

 olytic enzyme in Sarracenia, and its absence from Dar- 

 lingtonia. The Hquid in the pitcher is not antiseptic ; 

 bacteria are abundant, and, under the action of these, 

 decay of animal matter takes place. The products of this 

 decay may be absorbed by the plant. To what extent this 

 process supplements or is supplemented by the enzyme of 

 the plant, remains to be seen. Sarracenia seems to be on a 

 lower stage of organisation than Nepenthes ; the pitcher 

 is imperfectly supported and contains Uttle Uquid, the insect 

 trap is perhaps less efficient, the digestive arrangements 

 are incomplete. 



(d) Cephalotus follicularis, the Australian pitcher plant, 

 which is confined to the region of King George's Sound in 

 West Australia, has been Httle investigated. The leaves 

 are in a rosette and arranged in two tiers. The upper are 

 normal, flat and broadly elliptical. The lower are the 

 pitchers — short and fat with a very prominent ribbed rim, 

 a double wing down the middle, and a single wing at each 

 side. The rounded mouth is covered by an arched lid. 

 The hd is borne on a short stalk. A "slipping " zone is 

 present, and there are glands as to the functions of which 

 nothing certain is known. The pitchers are usually half 

 filled with fluid containing numerous small insects. How 

 these are utihsed we do not know. The brilUant red- 

 purple colouring of the outer side of the pitcher and of the 

 lid may be noted : " As the pitchers stand in a whorl under 

 thefoUage leaves ... the Cephalotus plant must be as striking 

 as if it bore brilliantly coloured flowers." 



{e) Of the Lentibulaxiaceee the simplest relations are 

 shown by Pinguicula. The British Pinguicula vulgaris, 

 the butterwort, is a common moorland plant ; two other 



