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 roots : 



Oxygen, 



Water. 

 Sahs of: 



Potassium. 



Calcium. 



Magnesium 



Iron. 



Nitrogen. 



Sulphur. 



Phosphorus. 



Fl 



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. 



Given off from the roots : 



Carbon dioxide. Possibly in some in- 

 stances organic acids and enzymes. 



Fig. I20. Longitudinal Diagram of a Plant. 



In this diag-ram the dotted liighiv'ay is the water conducting area, and the black hig-hway 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 



