DESCRIPTION OF THE COTTON PLANT 19 



of cellulose laid down within and upon the envelope; (c) 

 the core of cell-contents filling up the central cavity. 



If a cotton fiber be examined carefully under a magnify- 

 ing glass it will be found that it is broadest near or a little 

 below the middle and gradually tapers toward both the 

 base and the apex. If the fiber is mature this examination 

 will show the fiber-tube to be somewhat flattened and 

 irregularly twisted. It is claimed that the number of the 

 twists varies from 300 to 500 to an inch. The amount of 

 twist in the cotton fiber is very important in determining 

 its spinning qualities and, hence, its value. The degree of 

 twisting is, to a large extent, determined by the stage of 

 maturity of the fiber. The immature fibers, on drying, 

 form almost flat, structureless ribbons, with very little 

 twist. In almost any lot of cotton the following classes of 

 fibers may be recognized: (1) ripe; (2) half ripe, and (3) 

 unripe. In addition to these three classes, a fourth class, 

 namely, over-ripe fibers is often noticeable. In this class 

 the fibers are spoken of as being rod-like, devoid of elastic- 

 ity and unsuitable for spinning purposes. 



20. Length and strength of fiber. The length of 

 cotton fiber varies with different kinds of cotton, and to a 

 slight extent with soil fertility. Duggar l gives the follow- 

 ing as the approximately average lengths of fibers of the 

 principal kinds of cotton: 



Sea Island, 1.61 inches; 



Egyptian, 1.41 inches; 



American upland, 0.93 inches; 



American long-staple, 1.3 inches. 



The fibers vary in length even on the same seed. Those 

 at the base or pointed end of the seed are usually shorter 

 than those borne on the apex end. This is probably due 

 1 Duggar, J. F., "Southern Field Crops," p. 263. 



