132 



BOTANY FOR BEGINNERS 



CHAP. 



the door, which gives way and allows it to enter. It tries again 

 and again to push the door open but it will only open inwards. 

 After a time it dies ; decomposition sets in, and the products are 

 absorbed by the cells which line the bladder. 



In most parts of the world there are carnivorous plants. 

 Well-known examples are the Venus's Fly-trap (Fig. 154), which 



grows in South America, 

 and the Pitcher plants, 

 which are very widely dis- 

 tributed. 



Most of these plants 

 grow in soil which is 

 very poor in nitrates, with 

 lowly bog plants for their 

 companions. It is only 

 through their power of 

 entrapping small animals 

 that they are able to live. 

 It has been proved by 

 experiments that if car- 

 nivorous plants are grown 

 so that no animal food 

 can be obtained that they 

 are stunted in their 

 growth. 



Leguminous Plants 

 The members of the 

 Bean family can obtain 

 the nitrogen which they 

 require in a different way 



from most plants. If a Clover or Pea-plant is pulled up and the 

 roots examined, they will be seen to be covered with a number 

 of nodules, or root-tubercles, as they are called. These are 

 produced by Bacteria," which are themselves minute plants. The 

 Bacteria penetrate through the root-hairs into the cortex of the 

 root, and so produce the tubercles. The Bacteria live in and 

 around the tubercles in the soil, and take free nitrogen from 

 the air in the soil, and build up this nitrogen into compounds, 

 which are passed on to the plant. The plant most likely gives 

 carbonaceous compounds to the Bacteria in return for nitrogen. 



FIG. 154. Venus's Fly-trap. 



