BASS STRAIT. The channel separating Tas mania from Australia (Alap: Australia, G 6). It is about 1S5 miles long and from SO to 150 miles broad, and contains many small islands. The name of the strait is derived from that of Dr. George Bass, who first proved that Tas mania was an island by circumnavigating it in 1798.
BAST (origin obscure). A term originally applied only to the fibrous tissue occurring as the innermost layer of bark. These fibres are longer and more elastic than wood fibres, and often have considerable economic importance. The term has, however, come to have a more extended technical application. In the structure of the higher plants (ferns and flowering plants) a system of conducting vessels occurs ('vascular system'). These vessels are organized into strands called 'bundles,' each bundle consisting of two kinds of tissue, 'bast' and 'wood' In this way, each bundle is double. one part consisting of bast elements ('phloem'), the other of wood elements ('xylem'). The vessels which enter into the structure of the bast (phloem) region are called 'sieve vessels' or 'sieve tubes,' being elongated cells in whose walls there are perfo rated plates. In ordinary shrubs and trees there is a zone of actively dividing cells between the bast, and the wood called the cambium. This forms new bast on the outside and new wood on the inside, resulting in an annual increase in the diameter of the stem. In consequence of this, the bast or inner bark of the ordinary tree Gecurs in concentric zones. The bast varies ac cordingly in thickness, in fleshy roots and tubers representing most of the diameter. In trees in which the bark is not thrown off, the bast is very scanty, as in the beech, in which the entire bast zone in a tree TOO years old is only about 0.04 inch in thickness. if the bark is thrown
off, the bast is more abundant, the concentric zones often being conspicuous, but not indicat ing the age of the tissue. It is known, for ex ample. that in willows with a smooth bark a tree which is a dozen years old may not show more than three or four layers of bast; while in willows with a thick, rough bark, three or four concentric zones may be formed in a single year.
When the bast cells are first formed, they are like the cambium cells from which they are de rived, and they do not change so rapidly as the Nvood cells. Hence there is not such a sharp line between cambium and bast as between cambium and wood. The bast region or phloem contains both sieve tubes and bast fibres, the sieve tubes being the more important in the economy of the plant, for they serve to carry proteids from parts in which these substances are stored or are being formed to parts where they are to be used. In the true flowering plants, each sieve tube is ac companied by what is called a 'companion cell,' the two cells having arisen from the division of a common parent cell. The ordinary conifers and ferns differ from the true flowering plants in having no companion cells. The duty of the companion cell seems to be to help in the distri bution of the proteid substances contained in the sieve tubes.
The principal bast fibres in commercial use are those derived from the flax, hemp, jute. ramie, or china-grass, suns hemp, and Cuba bast, or re lated species of Hibiscus. See FIBRE and the names just mentioned.