Part 68. Bast Plant Fibers

Part 68. Bast fibers form, generally speaking, the strongest and most elastic part of the framework of plants. In contrast with the woody part they contain commonly a larger proportion of pure cellulose and are thus comparatively little affected by agencies of decay or the various chemicals which destroy or soften wood. The bast fibers of greatest economic importance are flax, jute, and hemp.

Flax Fibers

Flax is next to cotton, the most useful and valuable of all fibers. It has an even wider range of uses, but as its preparation requires more labor, it is more costly and hence more a fiber of luxury. The flax plant (Fig. 217) flourishes throughout the temperate zones, and was cultivated in the Old World even during prehistoric times. To-day the world's supply of flax comes chiefly from northern Europe.

Fig. 217, I.-Flax (Linum usitatissimum, Flax Family, Linaceoe). Plant in flower. Young flower-cluster. Seed, entire and cut vertically. (Baillon.)-Annual, about 60 cm. tall; leaves smooth; flowers light blue; fruit dry. Native home, Southeastern Europe and Asia Minor.

Fig. 217, II.-Flax. Flower, cut vertically. Pistil and calyx. Stamens and pistil. Floral diagram. Pod open for discharge of seeds. Seed, cut vertically. (Baillon.)

The bast of a flax plant forms the main strengthening element of its stem, running near the surface where, plainly, the strain is greatest. These fibers consist of nearly solid cylinders of almost pure cellulose. The essentials of the process by which pure flax is obtained are, first rotting or "retting" the stems and then, after drying them, breaking the weakened parts into fragments, and finally beating and combing these away from the bast. After further combing to separate the longest and best fibers, and then bleaching, they are ready to be manufactured into the finest linen fabrics as well as such strong materials as canvas and duck, and the foundation of carpets and oil-cloth. The strongest thread and twine, and the finest lace are also made from flax, while from linen rags are made the best papers for writing and artist's use. From this paper, by treatment with sulphuric acid, a "vegetable parchment" is made which fully takes the place of the parchment formerly manufactured from the skin of sheep.

Jute Fibers

Jute is obtained from two closely related species (Fig. 218). Though cultivated from very early times in India the fiber has assumed commercial importance only within the nineteenth century. The bast is extracted from the stem in somewhat the same way as flax. In luster and fineness it rivals flax, but as it contains less cellulose it is inferior in strength and enduring qualities. Its most important use is for coffee-sacks, cotton-bagging, burlap, webbing, and similar coarse fabrics. It is coming rapidly into use, however, for finer fabrics, imitating linen and silk, and as a substitute or adulterant of hemp it is used extensively in cordage; but it is ill-suited for this purpose on account of its rapid deterioration.

Fig. 218, I.-Jute (Corchorus olitorius (A) and C. capsularis (D), Linden Family, Tiliacece). A, flowering and fruiting top of pot-herb jute. D, flowering top of podded jute. (Schumann.)-Annuals about 2-3 m. tall; leaves light green; flowers whitish yellow; fruit dry, elongated in pot-herb jute, globular in the other species. Native home, India.

Fig. 218, II.-Podded Jute. Fruit. (Baillon.)

Hemp Fibers

Hemp (Fig. 171) is coarser than flax but longer and stronger. It is thus especially well adapted for twine, rope, and heavy cordage, and likewise for sail-cloth, bagging, and similar coarse fabrics. Tarred ravelings of hemp rope are extensively used under the name of oakum for calking the seams of wooden vessels and also the joints of iron pipes, and the like. The plant has been grown and its fiber used for many centuries in the Old World. At present the largest supply comes from Northern Europe, and the best quality from Italy. The method of treatment is much the same as for flax.