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CHAPTER XV. 



PHYSICAL STRUCTURE OF VEGETABLE FIBRES 

 AS SEEN UNDER THE MICROSCOPE. 



THE flax fibre as it is obtained from the plant and as 'it 

 appears in trade, is in the form of filaments of various length. 

 These filaments are composed structurally of small elements 

 or cells, which may be isolated by treatment with a dilute 

 chromic acid solution. These cells are cylindrical in form, and 

 taper to a point at each end, their average length being about 

 i J in. The ratio of the length of the fibre to its breadth is 

 about as i : 1,200. Under the microscope the surface of the 

 fibre appears smooth and marked longitudinally with frequent 

 transverse fissure lines and jointed structures. On treatment 

 with chloriodide of zinc the latter are coloured much darker 

 than the rest of the fibre, and are thus rendered more appa- 

 rent. The lumen appears in the centre of the fibre as a narrow 

 yellow line, and it is usually completely filled with protoplasm. 

 In cross section the fibres of flax are polygonal, with rounded 

 edges, show a large lumen and a relatively thin cell wall. In 

 these respects they are very similar to hemp, but may be dis- 

 tinguished from the latter, however, in that they do not 

 aggregate in thick bundles, but are more or less isolated from 

 each other, so that the cross section frequently shows but 

 one fibre, and seldom more than three or four. Other differ- 

 ences from hemp, exhibited by the flax fibre, are (i) the 

 lumen of the hemp fibre is seldom filled with yellowish proto- 

 plasm like that of the flax fibre ; (2) flax fibres end in sharp 

 points, whereas those of hemp do not. 



