118 ECONOMIC IMPORTANCE OF GREEN PLANTS 



man. An onion is a compact budlike mass of thickened leaves 

 wriich contain stored food. 



Cabbage 



Onions 

 Leaves used as food. 



Lettuce 



Stems as Food. — A city child would, if asked to name some 

 stem used as food, probably mention asparagus. We sometimes 



forget that one of our 

 greatest necessities, cane 

 sugar, comes from the 

 stem of sugar cane. Over 

 seventy pounds of sugar 

 is used each year by every 

 person in the United 

 States. To supply the 

 growing demand beets are 

 now being raised for their 

 sugar in many parts of 

 the world, so that nearly 

 half the total supply of 

 sugar comes from this 

 source. Maple sugar is 

 a well-known commodity 

 which is obtained by boil- 

 ing the sap of sugar maple until it crystallizes. Over 16,000 tons 

 of maple sugar is obtained every spring, Vermont producing about 

 40 per cent of the total output. The sago palm is another stem 



Celery Kohl-rabi Potato 



Stems used as food. 



Sugar cane 



