ECONOMIC IMPORTANCE OF GREEN PLANTS 119 



which supports the life of many natives in Africa. Another stem, 

 living underground, forms one of man's staple articles of diet. 

 This is the potato. 



Roots as Food. - - Roots which store food for plants form im- 

 portant parts of man's vegetable diet. Beets, radishes, carrots, 

 parsnips, sweet potatoes, and many others might be mentioned. 



The following table shows the proportion of foods in some of 

 the commoner roots and stems : - 



Fruits and Seeds as Foods. - - Our cereal crops, corn, wheat, 

 etc., have played a very great part in the civilization of man and 

 are now of so much importance to him as food products that bread 



Wheat 



Nuts Pear 



Seeds and fruits used for food. 



Melon 



made from flour from the wheat has been called the " staff of life." 

 Our grains are the cultivated progeny of wild grasses. Domesti- 



