Some Families of Angiosperms 



535 



They are mentioned here 

 merely because of the fact that 

 all three families are made up 

 of insectivorous plants. In 

 the pitcher plants the insects 

 die by drowning in the water 

 contained in the pitcher-like 

 leaves. In the closely related 

 sundews, the insects are caught 

 by the sticky secretion from 

 glandular hairs on the upper 

 surface of the leaves. In the 

 Venus' flytrap the blade of the 

 leaf consists of two halves which 

 fold together. On the upper 

 surface of each half are three 

 hairs and numerous small red- 

 dish glands. The margins of 

 the blades have tooth-like pro- 

 jections. When the hairs are 

 touched the two halves of the 

 blade suddenly close, the mar- 

 ginal teeth interlock, and small 

 insects may be caught. In all 

 these plants the insects are sub- 

 sequently digested and the prod- 

 ucts absorbed by the plants. 

 It is rather remarkable that 

 three such unusual habits should 

 have arisen within a single order 

 of plants. It should be stated 

 that all these plants may be 

 grown in conservatories with- 

 out feeding them insects. 



Fig. 



of Nepenthes, one of a group of tropical 

 epiphytes. These pitchers contain water 

 and are provided with glands that secrete 

 enzymes and absorb the products resulting 

 from the digestion of insects that drown 

 in them. 



