MORPHOLOGY OF LEAVES AND FLOWERS 



599 





Fig. 454. Section of leaf of Bromus mollis. Car, mid-nerve; L., leptome ; H, 

 hadrome ; B, bulliform cells ; Ste, stereome ; CB, chlorophyll bearing par- 

 enchyma ; EC, epidermal cells ; Tri, trichone. 

 (Sirrine and King.) 



FUNCTION OF LEAVES. 



Photosynthesis. This is the process by which sugar and starch 

 are produced for the plant. It is really a process of food manufac- 

 ture by which raw materials are made into plant food and is an 

 exceedingly important one, for upon it depends the lives of all 

 plants and animals. 



If an active leaf be submerged in water in the sunlight, bubbles 

 will be seen continuously forming on the leaf surface and rising 

 through the water. If light is excluded, the action will cease, and 

 by increasing and decreasing the amount of light, it will be found 

 that the process varies with the amount of light. An examination 

 of 4his gas will show that it is oxygen. It has also been found that 

 at the same time the oxygen is given off by the leaf, carbon dioxide 

 (CO..) is taken in, and that the outgo of oxygen and intake of car- 

 bon dioxide have a close relation. 



