DESCRIPTION OF THE CORN PLANT 



35 



parallel veins. On examining a cross-section of the leaf 

 under the microscope, each vein will be seen to contain a 

 fibrous bundle of various kinds of tissues, known as a 

 fibro-vascular bundle. In Fig. 14 are shown some of these 

 large, thick-walled cells, resembling somewhat the veins of 

 an animal ; and it is by means of these that solutions are 

 circulated through the leaf. These fibrous bundles ex- 

 tend into the stem and the roots, making a direct passage 

 for the transfer of soil solutions taken up by the roots 

 through the stem and out into the leaves. 



22. Air passages. — ■ Throughout the leaf tissues are 

 systems of air passages. These are connected with small 

 openings of the leaf surface, or stomata. Fresh air is con- 

 stantly coming into the leaf through these stomata, car- 

 rying carbon dioxid and oxygen, both of which are utilized 

 by the plant in connection with the minerals taken up from 

 the soil and elaborated into plant-food. 



23. Loss of water. — ■ As the air passes out of a leaf it 

 constantly carries out the water that has been taken up 

 from the earth. The outer covering, or epidermis, of the 

 leaf is impervious to water or air, but there are stomata 

 at regular intervals. The number of these is very great, 



