150 



LIVING PLANTS 



Varying tints 



Synthesis 

 of food 



In some cases the outer layers of cells of the 

 the leaf, or merely the walls of the cells, may 

 contain coloring matter. The number and 

 size of the chloroplasts, and consequently the 

 amount of the chlorophyll, may be greater in 

 some leaves than in others. Besides, the chlo- 

 roplasts may be moved about in the cell and 

 their distance from the surface of the leaf 

 altered, or they maybe placed in lines perpen- 

 dicular or parallel to the surface. In this 

 manner the infinite and elusive variations of 

 color, so fascinating to the lover of nature, 

 are produced in vegetation. The color of a 

 leaf may vary momentarily throughout the 

 day, as indeed does that of the entire land- 

 scape to the puzzled artist. 



The cell sap which bathes thechloroplast in 

 the leaves contains carbon dioxide absorbed 

 from the air. When the sun shines upon a 

 leaf the rays pass through the epidermis and 

 penetrate the cells containing the chloroplasts. 

 The chlorophyll converts a large proportion 

 of the light into heat and other forms of en- 

 ergy. With this energy as a motive power 

 the protoplasm of the chloroplast withdraws 

 water and carbon dioxide from the surround- 

 ing cell sap and combines them in such man- 

 ner that a substance known as formic alde- 

 hyde is formed and oxygen is liberated. In 

 a second stage the atoms of carbon, hy- 



