210 



CLIMBERS, PARASITES, SAPROPHYTES. 



In the Pitcher-plants, of which Nepenthes (Fig. 67) is the 

 best-known example, the whole or a part of a leaf is developed 

 as a pitcher with a lid attached to one side of the opening. 

 The bottom of the pitcher contains water, usually swarming 

 with Bacteria, and in Nepenthes a digestive ferment (pepsin) 

 is secreted, so that the insects falling into this liquid are 

 first drowned and then digested. The pitchers of Sarracenia 

 (Fig. 68) are also modified leaves, but instead of digesting 

 the captured insects they seem simply to absorb the products 

 of their decomposition by Bacteria. In these and other 

 Pitcher-plants, the lids of the pitchers are brightly coloured 

 and serve to attract insects, but they have no power of move- 

 ment, and cannot close when once they have opened. 



Fig. 67. Pitcher of Nepenthes 

 Distillatoria. 



Fig. 68. Pitcher of 

 Sarracenia. 



The rim of the pitcher bears honey- glands, which help in 

 attracting insects ; below the rim there comes a zone covered 

 with small glands sunk in pits on the inner surface of the 

 pitcher, then comes a smooth slippery region, the lower part 

 of which has hairs pointing downwards, and finally tne 

 lowest part containing water. Insects crawling over the 

 gland-bearing upper region soon reach the slippery zone, and 

 are prevented by the hairs below this from crawling up 

 again, so that they eventually fall into the liquid and are 

 drowned. 



