SOME USEFUL PLANTS AND PLANT PRODUCTS 325 



ancient times. At present, more than half of the world's 

 supply is raised in the southern United States. The cotton 



Fig. 179. — A field of cotton. 



fiber is a long, single-celled hair borne on the seed. The 



fibers are separated from the seeds by the machine Icnown as 



a cotton gin. Cotton yams are 



used in .the weaving of cambric, 



muslin, cheesecloth, duck, and 



other fabrics. Cotton threads 



are largely used with silk or wool 



in the weaving of mixed goods. 



Cotton treated with a solution of 



caustic soda is "mercerized"; 



the fibers are much changed and 



take on a silky appearance. 



Linen is made from the bast 

 fibers of the stem of the flax 

 plant. The varieties of flax that 

 are raised primarily for seed (from 



Fig. 180. — Cotton seeds 

 with fibers attached. 



