COTTON. 87 



Structure of Cotton Fibres. Cotton fibres are composed almost 

 entirely of pure cellulose, each being a unicellular hair. The wall of 

 the fibre is lined by a delicate layer of protoplasm or living substance. 



The cell-wall of the cotton hair grows by the accretion of new 

 cellulose material formed from the protoplasm. 



Fig. 63 shows a number of cotton fibres highly magnified. Fully ripe, 

 they are slightly twisted, and resemble to some extent a miniature stick 

 of barley-sugar. This spiral appearance is always a characteristic of fully 

 ripe cotton fibres. 



Of the four specimens shown in the illustration, the one on the right 



Fig. 61. Brazilian seed cotton. 



is a "Kempy" fibre, i.e., one that has been interrupted or crippled in its 

 growth. There is generally a less amount of twist in one part than in 

 the other, as can be seen by observing the point at which the interruption 

 occurs. These Kempy fibres do not take dyes so readily as do 

 those which are fully ripe. 



Fig. 64 shows three fully ripe fibres of Sea Island cotton. The 

 diameter of the fibres is remarkably uniform, and the spiral form very 

 distinct. When fibres are not ripe they become rod-like, with the spiral 

 feature suppressed. The want of this is a detriment to the spinning of 

 a good and reliable yarn, particularly in the finely-spun yarns for which 



