FIBER CROPS 



307 



and of the cell is the same, since the fiber consists of a single 

 cell; but in bast and structural fibers the length of the fiber is 

 many times the length of the single cells, since each fiber is 

 composed of many cells. Thus according to Wiesner the raw 

 fiber of flax varies from 8 to 55 inches in length, while the 

 length of the individual cells composing the fibers varies from 

 0.08 to 0.16 inch. 1 



The readiness with which the material that helps to hold the 

 individual cells together may be removed, as, for example, when 

 washed with soap, affects the wear when made into cloth, and 

 methods have been devised for determining the readiness with 

 which these and other substances may be removed as a partial 

 basis for judging the value of fibers. (400) 



The following outline classifies the most important fiber 

 plants of America into the three groups mentioned: 



395. Identification of Fibers. The simplest test for distin- 

 guishing animal from vegetable fibers is burning. Vegetable 

 fibers when thoroughly burned leave a white powdery ash, 

 while animal fibers leave a crisp coal. On account of the rel- 

 atively large percentage of nitrogen in animal fibers the am- 

 monia evolved may be recognized by the odor. 



Animal fibers which consist principally of nitrogenous com- 



1 Matthews: Textile Fibres, p. 99. 



