308 THE FORAGE AND FIBER CROPS IN AMERICA 



pounds are soluble in certain acids and alkalis, while vegetable 

 fibers, composed largely of carbohydrates under the general 

 term of cellulose, are insoluble in nearly all of the usual solvents, 

 although readily dissolved in a solution of copper oxide in 

 ammonia. Silk is more soluble in certain solutions than wool, 

 by which means they may be identified. While vegetable fibers 

 are not soluble in ordinary acids and alkalis, they may be dis- 

 integrated or greatly modified by solutions which will not injure 

 wool. Many processes of freeing wool from cotton and other 

 vegetable substances, such as seeds and burs, are based upon the 

 fact that weak acids and alkalis will disintegrate the cellulose, 

 after which the fragments may be shaken out. Many manufac- 

 turing processes, such as giving a silky luster to cotton, are 

 based upon the action of chemicals on the fibers. 



Woolen fibers can be recognized under the microscope by 

 the scales which point toward the outer end. Many of them 

 appear not unlike a series of baskets placed one within the 

 other. Silk and usually vegetable fibers have a smooth surface. 

 The cotton fiber is very much twisted. Different vegetable 

 fibers vary in color when treated with certain reagents. The 

 cells also vary in length, thickness, and shape, a knowledge of 

 which may help in identifying fibers. (399) 



396. Number of Fiber Plants. While there are hundreds of 

 plants that might be used for fiber plants, and while there are 

 30 to 40 plants which enter into the world's supply, and 20 to 30 

 which are used commercially in America, the most im- 

 portant of these from the standpoint of manufacture are cotton, 

 flax, jute, hemp, manila hemp, ramie, sisal hemp, and istle or 

 Tampico fiber. 



397. Production. Of cotton, America raises a great excess 

 for export, less than half the hemp required for local consump- 

 tion and practically none of the flax fiber, although producing 

 nearly one-half of the world's supply of flax seed, about 



