Chief functions of the leaf: 

 Photosynthesis. 

 Absorption of gases. 

 Absorption of the sun's energy 

 Transpiration. 



Important functions of the 

 leaf in common with other 

 plant parts: 



Synthesis of proteids. 



Respiration. 



Digestion. 



Absorbed by the leaf: 

 Sun's energy. 

 Oxygen for respiration. 

 Carbon dioxide for photosynthesis. 



Given off from the leaf: 

 Oxygen from photosynthesis. 

 Carbon dioxide from respiration* 

 Water by transpiration. 



Absorbed by the roots: 



Oxygen. 



Water. 

 Salts of: 



Potassium. 



Calcium. 



Magnesium 



Iron. 



Nitrogen. 



Sulphur. 



Phosphorus. 



Given off from the roots: 

 Carbon dioxide. Possibly in some in- 

 stances organic acids and enzymes. 



FIG. 120. Longitudinal Diagram of a Plant. 



In this diagram the dotted highway is the water conducting area, and the black highway is the area 

 for conduction of the food made in the leaf. The arrows indicate the direction of flow in these highways. 

 From Steven's " Introduction to Botany," copyright, 1902, by D. C. Heath & Company. Used by 

 permission. 



317 



