BAST, or BASS, the thin layer of fibrous tissue formed by, but outside the layer of, cam bium (q.v.), or in popular phrase the inner bark of dicotyledonous shrubs and trees. Less fre quently it occurs in the leaves and pith of dicotyledonous herbs and in the stems of cer tain monocotyledonous plants in which it is not easily distinguished from the wood. By ex tension the term is also applied to the phloem portion of the vascular system (q.v.) of flower ing plants and ferns. For the plant, as well as for mercantile purposes, bast is highly import ant, for until it becomes changed into wood, it conducts the elaborated food from the green tissue to regions of use or storage. The bast cells are disposed and developed variously in different plants; occurring in rows, wreaths, more or less spread bundles, or single within the parenchyma. In some plants bast is formed but once, in others every year. Some fibres are simple, others branched; some primary, others secondary; some ever limber, and some change to wood. They are most developed toward the outside of the stem. While young they contain a granulary liquid, which disappears by the thickening of their walls. Young bast cells when treated by a solution of iodine and chloride of zinc become pale blue, the older ones violet, the full-grown pink. Thickened cells are plainly stratified, and their walls often be come contiguous by the disappearance of the cavity. The walls exhibit various designs, spiral or other lines, more or less constantly, accord ing to the species of the plant. By micro scopical examination and chemical analysis the nature of the various fabrics made of bast may be determined. Thomson and F. Baur have thus demonstrated the sheets around Egyptian mummies to be of linen. The degree of con traction, of twisting, the length, density and form of the single cells of the bast vary in different plants. They are very long in flax, hemp, in some nettles, spurges, etc., very short
in cinchona. Cotton consists of long hairs, and not of bast cells, which it very much resembles otherwise. The bast cells of monocotyledonous plants are mostly lignified. They conduct elaborated food but a short time, become filled with air and thus dead to the plant. The un lignified are very hygroscopic and often contain chlorophyll. No bast cell has pits, but the conifers have sieve pores or canals. The uses of bast are manifold. Flax bast is soft, flexible, seldom with swellings; hemp bast is very long, stiffer and thicker than flax, more stratified; nettle (Urtica dioica) bast resembles cotton, has swellings and is thicker than hemp. Branched and lignified bast cells of great beauty are found in the mangrove tree (Rhizophora manple) and the secondary ones of Abies pectinate. Among the monocotyledonous bast fibres, those of the New Zealand flax (Phor mium tenax) are the most remarkable, being formed in bundles near the margin of leaves. They resemble hemp, are very white, sometimes yellowish, very long, and contain much lignin, in consequence of which they are somewhat stiff, but very tough and fit for stout ropes. In palms a highly developed body of lignified bast surrounds the vascular bundles, while bast bundles are found also in the bark, leaves and interior of the stem. A similar disposition i exists in the Dracena refle.ra, and in some Aroidea. Everybody knows the tenacity of the bast of the lime tree, which is hence called bass-wood. The Chinese grass-cloth is made of Boehmeria nivea or B. tenacissima. Manila hemp comes from Musa textilis; rice bags are made in East India from Antiaris toxicaria. From the use of bast in ancient times for writing upon, the Latin name of bast, fiber, has been applied to designate book. See also FIBRE; FLAX; HEMP; JUTE; RAMIE.