WHAT MAKES MAN GO 57 



manufacture food. The products, however, are 

 not of the same value. Science and experience 

 have selected a large number of plants whose 

 products are valuable to man and domestic 

 animals. The mere mention of wheat, oats, po- 

 tatoes, barley, buckwheat, corn, rye, sugar, apples, 

 bananas, etc., sufficiently emphasizes their im- 

 portance in maintaining life. There is no known 

 process by means of which man with all of his 

 scientific and inventive skill can manufacture one 

 of these food products as do the green plants. 



It has been well said that a plant cell containing 

 chlorophyll is the "chemical laboratory in which 

 was manufactured the food of the world." In 

 these microscopic cells containing bodies rarely 

 seen except by those taking courses in botany, is 

 decided the fate of nations. They cannot be hur- 

 ried in their work nor can they be compelled to 

 work in eight-hour shifts, three shifts in twenty- 

 four hours; but as of old, long before man lived 

 on earth, in the North Temperate zone, they work 

 only during the summer. The increase In the pro- 

 duction of any of the necessary foods, then, must 

 wait upon the activity of uncounted billions of mi- 

 croscopic cells that work only in their season. 

 When the chemical changes thus dependent upon 

 living protoplasm have taken place, the product 

 can be stored for longer or shorter periods of 

 time. Apples and potatoes will last till the next 



