20 FIELD CROPS FOR THE COTTON-BELT 



to the slower growth and later starting of the fibers on the 

 base of the seed. In the upland cotton there is, in addition 

 to the fiber proper, an " under-fleece " (called fuzz or 

 linters) which is very short, as a result of the failure of a 

 number of "cuticular cells" to elongate. 



The strength of the cotton fiber varies according to its 

 ripeness and fineness. From 2.5 to 15 grams represents 

 roughly its breaking strength. Williams, of North Car- 

 olina, found the average breaking strength of single fibers 

 representing twelve different varieties, to be 6.83 grams. 

 As a result of tests made by Hilgard the breaking strength 

 was found to vary, from 4 to 14 grams in upland cotton. 

 The cotton fiber, in proportion to its size, is stronger than 

 jute or flax and is three times as strong as wool. It is sur- 

 passed in strength by the fibers of hemp, manila hemp, 

 and silk. 



