Part 66. Plant fibers in general. Next to food-plants those producing fibers have proved the most useful of all the vegetable kingdom, and have contributed most to the advancement of civilization.

Mankind while yet in the stage of savagery needed some sort of cordage easier to procure than sinews or strips of hide, and more suitable for bowstrings, snares, fish-lines, nets, baskets, and the like. He needed also some form of clothing less cumbersome and cooler than that afforded by the skins of animals. These needs were admirably met by twisting, plaiting, or weaving the flexible strands which he found strengthening roots, stems, and leaves, or by spinning the woolly covering of seeds. We know that sheep's wool and other animal fibers, including the silk of which the silkworm makes its cocoon, were used very early in certain regions as materials for fabrics, but in general it is safe to say that vegetable fibers have been far more extensively used than animal fibers even from prehistoric times.

As civilization has advanced, and man's needs have multiplied, the uses of vegetable fibers have also multiplied, and their importance in daily life has increased enormously. To-day as their properties are better understood and their wonderful possibilities more fully realized, these fibers are coming to be used more and more in place of animal fibers and other animal products. It is true that mineral fibers, such as asbestos and spun glass, and metals in the form of wire, are replacing vegetable fibers to a limited extent; but in spite of this the consumption of fibers from plants is steadily increasing. They are now used most extensively as materials for fabrics, cordage, plaiting, matting, wickerwork, thatch, brushes, stiffening, filling, paper, and various cellulose products.

Fabrics are made of especially flexible fibers spun or twisted into yarns, threads, or cords, which are then variously intertwined by weaving, braiding, knitting, or netting. According to its texture a fabric may serve for wearing apparel, house-furnishing, decoration, awnings, sails, tape, belts, girths, webbing, burlap, gunny bagging, hammocks, nets, or lace. The finer fabrics are among the greatest triumphs of human skill and constitute the most highly developed of fiber products. Cordage includes yarn or thread for sewing or needlework, twine, fish-lines, cords, ropes, and cables. These consist, for the most part, of especially strong fibers, which are twisted into strands and then "laid" or twisted again in such a manner that they will not freely untwist. Plaiting consists of flat fibrous strands sufficiently pliable to be folded into plaits or flat braids and used for straw hats, fine basketry, and the like. Matting consists of elastic fibrous strands woven or braided into mats or screens. Wickerwork is made of supple twigs, strips of wood or similar fibrous strands interlaced to form hampers and other stout baskets, or chairs and similar articles of furniture. Thatch consists of strips of fibrous material, overlapped and fastened so as to shed water, as on a roof. Brushes, including brooms and whisks, require fibers of special stiffness and elasticity. Stiffening, which is mixed with plaster like cow's hair to give cohesion, calls for fibers which are at once strong and able to resist the softening influence of the plaster. Filling, such as the stuffing used in upholstery, calking for the seams of water-craft, casks, etc., and packing for objects to be transported, require light fibrous material so soft and elastic that it will fully occupy the spaces into which it may be crowded. Paper consists of fibers, especially rich in cellulose, which have been softened and compacted, and finally pressed into sheets or molded into other forms as papier-māche. Besides the more familiar uses of paper for writing, drawing, printing, book-binding, boxes, and so on, there are many others of considerable importance. Thus we have paper garments, paper napkins and other substitutes for fabrics used in the household, paper pails and similar articles replacing wooden ware, paper canoes and paper car-wheels. Such wheels having steel hubs and tires, are found to wear far better than wheels made wholly of steel. Fine paper is nearly pure cellulose. The larger the percentage of cellulose in a fiber the better the paper it makes. Fibers rich in cellulose are also the source of various cellulose products, obtained by chemical means presently to be described. These products include guncotton which is a high explosive used in the manufacture of smokeless powder; collodion, of much use in surgery as a covering for wounds; celluloid, the well-known substitute for ivory, bone, tortoise-shell, and similar materials; and artificial silk which is coming to be used widely in place of the product of the silkworm.

From what has been said of the great variety of uses to which fibers are put, it follows that the term fiber must have a rather broad definition. Fibers may be either fine or coarse, flexible or stiff, elastic or soft. They differ also in structure and chemical composition, and in the part from which they are derived. They agree, however, in being comparatively slender structures, which although separately weak, form strong yet pliable articles of manufacture when twisted, woven, or otherwise intimately joined together. If we define fiber-plants as those which yield slender parts of economic use when thus united, it may be said that over a thousand species of them are known to be used more or less in various parts of the world. The great majority of these, however, are used only in restricted regions and are not cultivated. Less than fifty are of much commercial importance. Of these the most useful are the species yielding cotton, flax, jute, hemp, and manila.

Fibers may be classified most conveniently for our present purpose into the following groups: (1) surface fibers, more or less hair-like outgrowths; (2) bast fibers, consisting entirely of such tough strands as form the bast or strength-giving part of the inner bark of stems; (3) woody fibers, composed entirely of wood; (4) mixed fibers, containing both woody and bast-like fibers; and (5) pseudo-fibers, which consist either of entire plants or of parts lacking both wood and bast.