PHYSICAL STRUCTURE OF VEGETABLE FIBRES 93 



The ultimate fibres of the jute plant, as seen under the 

 microscope, are relatively short, being only about i- in. in 

 length and yj n in. in breadth. In cross section the jute fibre 

 shows a bundle of several elements bound together, these 

 being more or less polygonal in outline, with sharply defined 

 angles. Between the separate elements is a narrow medial 

 layer. The lumen is usually of about the same width as the 

 cell wall, and in cross section is round or oval. Longitu- 

 dinally the lumen shows remarkable constrictions, though 

 towards the end of the fibre the lumen broadens out consider- 

 ably, causing the cell wall to become very thin. Externally 

 the fibre is smooth and lustrous, and has no jointed ridges or 

 transverse markings such as are seen on flax or most other 

 bast fibre. 



Microscopically the ramie fibre is remarkable for the large 

 size of its bast cells. These are, on the average, about 6 in. 

 in length and n in. in breadth. Joints and transverse 

 fissures are of frequent occurrence along the fibres. The 

 lumen is quite broad and easily noticeable. The ends of the 

 ultimate fibres have a thick-walled, rounded point, and the 

 lumen is reduced to a line. The cross section of the fibre 

 shows usually only a single element or a group of but a few 

 members. The cross section is elliptical in shape, and the 

 lumen appears open, and frequently contains granular matter. 

 The fibres are frequently very broad, and at these parts are 

 flat and ribbon-like in form, and are never twisted. 



In its microscopic characteristics Gambo or Ambari hemp 

 is very similar to jute. The length of the ultimate fibres is 

 about i in. The median layers of lignin between the cells are 

 broad. The lumen presents the same appearance as with jute, 

 having such very marked contractions that in .places it is 

 discontinuous. The ends of the fibres are very blunt and 

 thick-walled. 



Cotton fibre may be readily differentiated from other fibres 

 on account of its pronounced microscopical characteristics. 



