THE NUTRITION OF PLANTS 



165 



swallowed by animals. Some common illustrations are as 

 follows : 



(1) Pitcher plants. — In these plants the leaves form 

 tubes, or urns, of various forms, which contain water, and 

 to which insects are attracted and drowned (see Fig. 146). 

 A pitcher plant common throughout the Southern States 

 may be taken as a type (see Fig. 147). The leaves are 

 shaped like slender, hollow cones, and rise in a tuft from 



the swampy ground. 

 The mouth of this 

 conical urn is over- 

 arched and shaded 

 by a hood, in which 

 are translucent spots, 

 like small windows. 

 Around the mouth 

 of the urn are 

 glands, which se- 

 crete a sweet liquid 

 {nectar), and nectar 

 drops form a trail 

 down the outside of 

 the urn. Inside, just 

 below the rim of the 

 urn, is a glazed zone, 

 so smooth that insects 

 cannot walk upon it. 

 Below the glazed zone 

 is another zone, 

 thickly set with stiff, 

 downward-pointing hairs, and below this is the liquid in 

 the bottom of the urn. 



If a fly is attracted by the nectar drops upon this curious 

 leaf, it naturally follows the trail up to the rim of the urn, 

 where the nectar is abundant. If it attempts to descend 

 within the urn, it slips on the glazed zone, and falls into 



Fig. 155. 



A sun-dew, showing rosette habit of 

 the insect-catching leaves. 



