CHAPTER IV 



LKAVKS 



'1'^ hax'e learned in the pre\'ious chajj- 

 tcrs that the roots are the means by 

 hich a ])hint t^^athers out of the earth 

 hr \ari()us constituents which are need- 

 Lo maintain its h'fe. 

 The Iea\es ha\e also to do their part in collect- 

 ing from the air such gases as are required to 

 effect the processes carried on within the substance 

 of the leaf. 



The leaf is really the digestive (jrgan of the 

 l)lant ; it feeds, breathes, and gives off in the form 

 of vap(jur an\' excess of water not required for its 

 work, ^^)r these purposes sunlight and air are 

 necessar)-. 



A leaf consists of a stalk, called a petiole, and 

 the flat green part, which we may call the blade. 



