" Photosynthesis," or Sugar and Starch 

 Manufacture 



THE GREEN PLANTS OF OUR WAR GARDENS STAND FOR THE MOST 



FUNDAMENTAL OF ALL THE WORK OF THE EARTH: THEY 



ALONE CAN MAKE FOOD FROM THAT WHICH IS 



NOT FOOD— FROM EARTH AND AIR 



By JOHN M. COULTER 



Professor and Head of Department of Botany, University of Cliicago; President of the American 

 Association for the Advancement of Science; Founder and Editor, Botanical Gazette 



Ar THIS time we are much con- 

 cerned with our national re- 

 L sources. Much of our business 

 has been reorganized to supply the ma- 

 terials needed, and as a consequence, 

 we think of the essential work in terms 

 of manufacture and transportation, 

 work that depends upon the activities 

 of men. Of course all this work is es- 

 sential, but it is made possible by a still 

 more fundamental process which should 

 be realized. Men could not work with- 

 out food and materials, but few realize 

 how these are produced. In fact, so 

 little thought was given to food pro- 

 duction before the war that our popu- 

 lation was increasing very much faster 

 than our food production. This was 

 the most important material problem 

 this nation was facing before the war, 

 and it became very acute as soon as we 

 entered the war. 



If men cannot work without food, 

 neither can they work without mate- 

 rials, and fundamental among mate- 

 rials are wood and coal. Food and wood 

 and coal may be regarded as the basis 

 of our activities, and still very few 

 know how these essential things are 

 produced. They are made hy green 

 plants! The results of the work of 

 green plants are food used directly or 

 .transformed in the bodies of food ani- 

 mals, coal deposits, forests of timber. 

 Green plants have sometimes been 

 characterized as the mediators between 

 death and life, and this is true, in that 

 through their work a dead world is 

 transformed into a living world. They 

 426 



stand at the threshold of our life, of 

 our resources and activities. 



The word photosynthesis may not 

 suggest its meaning to many people, 

 but it stands for the most important 

 process in the world. It is primarily 

 the fundamental process of food pro- 

 duction without which the world of 

 organisms, including ourselves, could 

 not live. Photosynthesis is chiefly the 

 work of the foliage, because the 

 leaves represent the greatest display of 

 green tissue. To most of us foliage is 

 simply a thing of beauty in a park or a 

 landscape, but we must realize that it is 

 also a laboratory for food manufacture, 

 upon which the world depends. In this 

 laljorator}^ inorganic materials are built 

 into organic substances, and upon 

 these organic substances the green 

 plants live and provide an excess suf- 

 ficient to feed animals — and also those 

 plants which are not green, such as the 

 mushrooms and other fungi. 



There are several general kinds of 

 food as man classifies them, but the 

 work of green plants has to do first and 

 foremost with carbohydrates, such as 

 sugar and starch — which, however, are 

 in turn the basis for the manufacture 

 of other foods. 



The raw materials used in carbohy- 

 drate manufacture are a1)out the most 

 widely distributed materials on the 

 earth; namely, water and carbon diox- 

 ide. The occurrence of water needs no 

 explanation, while carbon dioxide is 

 everywhere in the air. Green plants 

 can manufacture food therefore wher- 



