FIBRE. In the commercial sense the un modified term "fibre" signifies the vegetable tissues used in the arts, and does not include the animal fibres, such as wool, hair and silk, which are classed as textile fibres, along with, however, several of the vegetable fibres, as cotton, linen, ramie, etc. Vegetable fibre is derived from the cellular structure or tissue of plants, the cells of which vary in diameter from one three-hundredth to one five-hundredth of an inch, the smaller sizes admitting of 125,000, 000 cells to a cubic inch. The walls of these cells are composed of a substance of starch like chemical composition, called cellulose, en closing the living element of the plant, known as protoplasm. There are three forms of cells, simple cells, woody cells and ducts. Woody fibre is formed by the lengthening and thicken ing of simple cells- The ducts or vessels are large cylindrical cells whose walls have been absorbed and broken away. Wood cells con sist of tubes one or two thousandths of an inch in diameter, their ends pointed and overlapping, so that when detached they form a continuous thread of cell structure of fibre proper, such as a filament of flax; and when they occur in the bark of dicotyledonous plants, or exogens, they are known as bast fibre. In monocotyledons, like the palms, and the century plant, the fibrous cells are built up with vessels into a com posite structure known as Cfibrovascular bun dle?' These bundles of elongated, thickened cells pressed firmly together, and often em bedded in soft cellular tissue, constitute, so to speak, the bones or structural part of the plant, and are called structure/ fibres, sisal hemp be ing an example. Even the common or simple cells form a valuable fibre material when they are produced on the surfaces of the leaves, stems and seeds of plants, in the form of hairs. This form of fibrous substance is known as surface fibre, cotton being an example. In this instance the hairs envelop the seeds produced in the boll or capsule. The Mown" on the
stems and surfaces of the leaves of plants is another example.
The term fibre is also given to other forms of vegetable growth where the fibrous material is not employed in the form of detached fila ments, like flax sisal and cotton. The stems and twigs, and even wood of exogenous trees, divided into splints and used for basket-making are designated as fibre; and in like manner the stems and leaves of endogenous plants split or used entire, as rattan, or when coarsely sub divided for plating into such articles as hats, mats, etc., are also classed commercially as fibre. The stripped epidermis of palm leaves, such as the raffia of commerce, is considered fibre, yet it is not in any sense filamentous. Even some species of mosses, marine weeds and fungous growths, on account of their economic employ, ment, are regarded as fibre substitutes, and are mentioned in the category of fibres. In general terms, however, fibre° is composed of bundles of bast or fibrovascular tissue in the form of long flexible filaments, such as flax, hemp or manila; or of hairs, such as cotton, capable of being twisted or spun into yarns or threads, to be manufactured into fabrics or cordage.
The following classification illustrates the different forms of fibrous material recognized by experts and shows the positions of the different fibres in their relations to each other: All fibrous material is classed in two grand divisions: A, Fibrovascular structure and, B, simple cellular structure. A is again divided into three groups: (1) Bast fibres; (2) Woody fibres, and (3) Structural fibres; B is divided into two groups, (4) Surface fibres and (5) Pseudo-fibres or false fibrous material.
1. The bast fibres are derived from the inner fibrous bark of the stems of dicotyledonous plants and are composed of bast cells, their ends overlapping to form in mass a continuous filament. Their utility is to give strength and flexibility to the tissue.