185 



with their diameter. The method of growth, according to Bowman* 

 is by the successive linear development of cells, the walls of which are 

 absorbed at the point of contact until an elongated cell is produced, 

 which constitutes the cotton fibre. The continued growth of this mass 

 of fibre assists in bursting open the pod when the period of maturity 

 is reached. The length of the fibre varies considerably on different 

 parts of the seed, being longest on th p crown and shortest at the base. 



It is claimed that the fibres do not attain their full length until the 

 pod has be ; n opened and the fibres are exposed to the drying and ri- 

 pening effect of the air and sun. 



In their earliest stages the young fibres appear circular in section, 

 but with their increase in length, the walls become thinner and finally 

 collapse into a flat, thin-walled fibre in appearance like a thin trans- 

 parent ribbon. With the opening of the boll there is a rapid consoli- 

 dation of the liquid cell contents, which by being deposited on the in- 

 ner side of the walls give to the fibre a greater thickness and density. 

 As the degree of maturity is increased the fibre once more becomes 

 rounded in section. As this action is not perfectly regular, owing to 

 the unequal pressure and deposition of the cell contents, the fibres be- 

 come twisted, a character readily recognized under the microscope, 

 and one that distinguishes cotton from any other fibre. 



In the eaily period of their formation the cells are filled with astrin- 

 gent juices whose presence may be recognized by applying the tongue 

 to the cut surface of an immature boll. During the process of ripening 

 these juices are replaced by others of a neutral or saccharine nature, and 

 when perfectly ripe the cotton fibre consists almost entirely of cellulose. 



When viewed under a microscope the general appearance of a cotton 

 fibre is that of an irregular, flattened, and somewhat twisted tube, the 

 tubular form sometimes being lost in the completely flattened fibre. 

 The edges of the fibre are somewhat thickened and slightly corrugated. 

 The hollow tubular character and constant diameter of the fibre are 

 maintained for about three-fourths its length, when it tapers to a point, 

 where it is perfectly cylindrical and often solid. From various causes 

 there are often found solid places in the body of the fibre, and where 

 such places exist, the quality of the staple is reduced, owing to the in- 

 equality with which such fibies take up dvestuffs. - 1*! 



The twist in the fibre, which seems to be an acquired character not 

 possessed by wild cotton, is explained by Monief as follows : 



The rotary motion begins with the process of vacuation in the fibre, 

 caused by the withdrawal of some of the fluid in the fibre when the seed 

 begins to ripen, and as this is effected slowly and progressively, be- 

 ginning near the extremity farthest from the seed and gradually re- 

 ceding toward the base, the free end or point becomes twisted on its 

 own axis several times, thus producing the convoluted form exhibited 

 under the microscope. 



In every lot of cotton three classes of fibres may be recognized — 

 (1) unripe, (2) half-ripe, and (3) ripe. These conditions are dependent 

 upon several factors, the most important of which is the gathering of 

 cotton before it has been exposed for a sufficient time to the ripening 



* Structure of the Cotton Fibre, p. 25. 



f The Cotton Fibre, its Structure, &c, p. 25. 



