WORK OF THE BEAN LEAF 



277 



roots, or the seeds of the plant, and the tracks for carry- 

 ing the food to the storehouse are the sieve tubes of the 



Figure 268. — Germination of a Monocotyledon. 



flbrovascular bundles. Part of the carbon dioxide is fur- 

 nished by the plant's own respiration. The plant takes 

 from the carbon dioxide all of the carbon, but only a part 

 of the oxygen, leaving 



some of it to be thrown r~\ ft]) "i 1 ! 



off as waste. 



The waste oxygen 

 thus set free by the leaf 

 in the manufacture of 

 food can now be used by 

 animals in respiration. 

 Animals are constantly 

 setting free carbon di- 

 oxide which plants must 

 have if they are to make 

 food. Animals will never 

 be able to use up all of 

 the oxygen in the air so 



Figure 269. 



Rootlets of Two Corn 

 Plants. 



Showing how they strive for food 

 and moisture. 



