PLANT LEAVES 



28? 



LESSON LXXX 



PLAXT LEAVES 



Work of leaves. The main object to be brought out 

 in the study of this lesson is the great work that leaves 

 have to do, and the important relations they sustain to 

 the life of the plant. 



1. Leaves spread out a great surface through which 

 the plant takes in oxygen, necessary for its life and 

 growth. 



2. Through this expanded leaf-surface the carbon- 

 dioxide gas of the air enters, and in the sunlight the 

 green leaf makes plant food out of the carbon-dioxide 

 and the minerals brought up in solution from the soil. 

 As one result of this process in the leaf, oxygen is set 

 free. 



3. After the leaf has used all the food-material 

 a needed from the sap-solu- 



tion brought up from the 

 soil through the roots and 

 stem, the excess of water is 

 thrown off by the leaf. This 

 is called transpiration. 



A great amount of water 

 is passed out of some plants 

 in this way. In the corn 

 plant about 275 pounds of 



water are P assed through 



the plant for each pound of 

 dry matter in the corn. In 

 oats almost double this amount of water is handled by 



FIG. 87. 



MAGNIFIED SETION 



S BR E EA T F Hir 



