Il6 COMMERCIAL FIBRES. 



diameter of the field unicellular, flat, but with thickened edges, so 

 that frequently one would say the sides of the fibre were concave 

 rather than flat, always with more or less of a twisted appearance. 

 The fibres of cotton, having only a single layer of cellulose for their 

 cell walls, are easily collapsed. While the cells of linen and of all 

 kinds of fibre consisting of a liber structure are cylindrical or nearly 

 so. When cotton hairs are growing they are full of protoplasm; as 

 soon as they become ripe, however, the protoplasm is absorbed and 

 the thin delicate walls, unable longer to retain their youth and full- 

 ness, become wrinkled and collapsed, looking very much like a 

 twisted bit of old ribbon. Any one can see how the cotton hairs 

 look when they are ripe and ready to be gathered, before they have 

 reached the manufacturers' hands, by examining the cotton from 

 our common cotton batting, or by examining the hairs on the sur- 

 face of the leaf in the white foliage plant called "dusty miller." 



Linen comes from the inner part of the bark of the Flax plant 

 Linum, and is cellular in structure. There is a central opening run- 

 ning the entire length of the fibre. It sometimes is not possible to 

 see it all the way without treating the fibre with some reagent to 

 bring it out. The cell walls are much thickened by secondary depos- 

 its and are tougher than ordinary wood fibre. The firm consist- 

 ency of the walls keeps the fibres full and round so that linen is 

 never found collapsed like cotton. Occasionally the cells are 

 pointed but generally the ends are square. Sometimes the cells are 

 of nearly the same length as their breadth, though generally much 

 longer. The secondary deposits on the cell wall are quite uneven, 

 so that some cells have a much larger central cavity than others, 

 and occasionally a cell wall will be exceedingly thickened. These 

 layers of cellulose peel off in strips, giving a rough appearance to 

 the surface. When boiled in potasic hydrate or treated with the 

 stronger acids faint spiral markings appear on the cell walls. Jute, 

 flax and hemp are very similar, though coarser than linen. 



The individual cells of jute are rather longer than those of 

 linen. Generally of a greyish-brown color, appearing like dead 

 cellulose. Quite a prominent central cavity with smooth edges is 

 present, seeming to be perfectly empty. Much more uniform than 

 in linen. It is apt to break straight across when broken at the ends 

 of the cells, but breaks with a long fibrous fracture if broken any- 

 where in the middle of the cell. 



