14 STRUCTURE AND PROPERTIES 



5. Fibres and Layers. When a branch of a 

 vascular plant is cut transversely, a certain 

 number of points are observed, which are of a 

 more compact character than the rest of the 

 structure. If the branch be divided length- 

 wise, we shall perceive that these points are the 

 ends of so many longitudinal threads, which will 

 separate from the rest of the tissue more readily 

 than they will themselves break. These threads 

 are called fibres. With a microscope we can 

 see that each fibre is composed of bundles of 

 vessels, bound up and intermixed with cellular 

 tissue. If we macerate the branch in water, 

 after some time the fibres separate of themselves, 

 as in the case of hemp, flax, &c. This separa- 

 tion in reality disorganizes the vegetable struc- 

 ture; the water first dissolves the softer parts, 

 i. e. the true cellular tissue, and so releases the 

 fibres which it held together, and if the process 

 be continued, the disorganization proceeds still 

 farther, and a homogeneous pulp alone remains, 

 as is seen in the manufacture of paper, where 

 the fibres which had formed the thread are ar- 

 tificially torn and reduced to a pulp, in which, 

 however, a good microscope will still shew us 

 the remains of a fibrous structure. This des- 

 cription of the structure of fibres explains why 



