PLANTS PROM AN ECONOMIC STANDPOINT 341 



from the fibers of flax. Flax is also grown for its seed, 

 from which linseed oil is made: Hemp has a coarse 

 fiber not suitable for clothing. Its fibers are used for 

 loosely woven materials such 

 as burlap, and also for ropes. 



Weeds. -- Weeds are 

 plants that have little or no 

 economic value. They are 

 plants that in some particu- 

 lar place are not wanted. 

 In a garden all the plants 

 which are not cultivated as 

 flowers or vegetables are 

 weeds. In a tennis court all 

 plants are weeds. Most 

 weeds seem to be unusually 

 hardy. They possess great 

 ability to disperse their seeds 

 and to resist the extremes of 

 climate and the attempts of man to eradicate them. They 

 flourish in poor soil and in fertile soil. They preempt 

 the soil and absorb the plant food so that other plants 

 are crowded out or die from lack of food. A number of 

 weeds are so persistent in their growth and spread so 

 rapidly that the United States Department of Agricul- 

 ture has classed them as national pests and has adopted 

 radical measures leading to their extermination. 



Weeds have some real value. They help to make 

 soil and to renew soils in worn-out regions. When soil, 

 through poor farming, becomes too poor to grow crops, 

 weeds will still grow on it and build up the soil. Weeds 

 are also valuable in that they force farmers to cultivate 

 the land. 



FIG. 303. A Cotton Plant. 



