feet, which as it ripens and becomes dry curls up into a circular form, resembling a thick piece of wire. Although raw esparto differs greatly in appearance and in structure from straw, yet it closely resembles straw when reduced to ultimate fibres by treatment with caustic soda. The fibres of straw and esparto have one peculiarity in common which distinguishes them from other paper-making fibres, viz., the shortness of the isolated cells. For this reason the structure is not altered or modified through the process of beating to any serious extent, so that the fibres in a well-beaten esparto paper still resemble closely the raw isolated fibres from boiled esparto pulp which has not been beaten. The bast cells are short, smooth 8 Fig. 139.-Esparto Fibres, according to Herzberg. fibres, cylindrical in form, tapering off to fine rounded points, having a minute central canal. In addition to the bast cells, the esparto contains epidermic cells of varying length and of curious shape having serrated edges. The presence also of small pear-shaped vessels, some short and others long, the source of which is to be found in the hairs attached to the surface of the leaf, is a certain indication of esparto. Straw. This has been used as a paper-making fibre since 1800. Between the years 1870 to 1890 enormous quantities were utilised for news and cheap printings, but the fibre has now been superseded by wood pulp. A certain quantity is, however, still employed, since it imparts a hardness to common printings which cannot be obtained with wood. The main portion of the straw now used in paper-making is submitted to a very slight chemical treatment, and converted into straw boards. The bast cells are long, thin fibres of cylindrical form with a small central canal, not clearly discernible with low powers. The cells when bent, which they often are, as examined under the microscope, do not assume a graceful curved form like esparto, but usually kink at the bends as a rubber tube will when folded L Fig. 140.-Straw Fibre, according to Herzberg. 1, 2, Bast cells; 3, 4, 5, Spiral vessels; 6 7, Parenchyma cells; 8, 10, 11, Epidermal cells; 9, Sclerenchyma cells; 12, Pitted vessel. sharply. The cells are slightly thickened at intervals, not externally, but internally, giving the central canal a varying diameter. Judicious colouring with the microscopic reagents gives a clearly defined structure. In addition to the bast cells, the straw is recognised by the presence of parenchyma cells, which are specially characteristic of straw. These vary in size, being cylindrical yet somewhat flattened and of different lengths, and usually covered with small pores. The epidermic cells are of all sizes, having deeply or slightly serrated edges similar to those of esparto, from which it is not easy to distinguish them. Usually the esparto serrated cells are more uniform in shape and size, while the straw cells are very irregular, particularly if the straw is a mixture of various sorts, such as wheat, rye, barley, and oats. The straw may be still further identified by the short, broad, oval-shaped cells found in the pith adhering to the interior portion of the plant stem. The cells of the different straws vary in shape and size, but possess certain general characteristics of the nature described. 6 7 3 Fig. 141.-Chinese Rice Straw. Fibres closely resemble ordinary wheat straw. 1, 2, Bast cells, of varying diameters; 3, End of bast cell, very 7, Pitted vessel. Hemp. A fibre characterised by its great strength. The paper-maker uses hemp in the form of canvas, sail-cloth, rope, and spinning refuse, all of which can be worked up. The material cannot be bleached to a high degree of whiteness, but its strength renders it suitable for the production of banknote and ledger papers, and it is used very largely in conjunction with rags for this purpose. When partially boiled, it is converted into browns and wrappers, being also used for cable insulation purposes. The term "hemp" covers a variety of plants. Hemp. Cannabis sativa-Species obtained from Russia, Mauritius, and various parts of India. Manila hemp. Musa textilis.-Found principally in the Philippine Islands. Sunn hemp. Crotolaria juncea. Found in India and known sometimes as Bombay or Madras hemp. In the raw state certain The hemp fibre resembles linen very closely. differences in structure serve for the purpose of identification, such as the striations parallel to the length of the fibre, fine transverse markings across the surface, broad flattened ends, sometimes fork-shaped, and small projecting hairs at some of the joints. These differences cannot be relied upon with certainty when the fibre has been converted into paper, for they become so modified and altered that identification is extremely difficult. A well-beaten hemp paper will exhibit a large number of fibrillæ or small fibres produced from the hemp by continued beating, which, when treated with the ordinary zinc chloride and iodine solution, will remain almost colourless. A similarly beaten linen paper will not show this peculiarity to the same extent. To distinguish an all-linen paper from an all-hemp paper is not such a difficult matter, but the determination of the quantity of linen in a ledger or deed paper made from a mixture of linen cuttings and canvas is in many cases almost impossible. 5 Fig. 142.-1-5, Hemp fibres (Herzberg); 6, Ends of Hemp fibres highly magnified. Manila Hemp. Closely resembles jute, not only as it appears after the beating necessary for the production of paper, but also in the raw state. The fibres are somewhat larger in diameter, and the cell walls are marked with pores, which, however, do not show very distinctly. A paper containing manila hemp is distinguished by occasional groups of small narrow cells with semicircular ends which are not found in jute. The central canal is not quite so varying in diameter as in the case of jute. The ultimate fibre is much shorter than in the true hemp; the canal being more distinct. Jute. A material resembling hemp in general appearance, which is worked up by the textile manufacturers into cloth and bagging, which eventually find their way into the paper-mill. It is frequently found mixed with hemp in inferior qualities of rope and canvas. The jute fibre is seldom used in white papers, being usually employed for browns and wrappers. The raw fibre is chiefly recognised by the very irregular shape and varying diameter of the central canal, which will be broad in some places and very thin in others. The fibres also frequently occur in bundles or filaments, which, however, are found separated in bleached stuff. The presence of knots is also characteristic of the jute fibre, and these are easily seen when the zinc chloride and iodine solution is applied. Jute is frequently found in papers supposed to be made entirely of hemp, owing to the fact that the canvas and rope used is often adulterated with jute. The presence of jute in such cases cannot be attributed to a deliberate addition of the material by the paper-maker 1 2 3 Fig. 143. Jute fibres (Herzberg). for the purpose of adulteration, as he may be quite ignorant of its existence in the raw fibres. Wood Pulp. The introduction of paper making fibre manufactured from wood dates from 1846, when Keller brought out a process for the manufacture of mechanical wood pulp. In 1866 Tilghmann patented a method for the production of chemical wood pulp, and since that date the consumption of this material has reached an enormous figure. The chemical pulp is used in all kinds of paper, either by itself or in conjunction with other fibres, but mechanical wood is only suitable for cheap printings and boards. The trees which furnish the best wood for this purpose are the Conifera, such as the common spruce and silver fir found in Europe, and the black spruce, white spruce, and American pine of the United States and Canada. Generally speaking, all soft woods, such as spruce, pine, fir, aspen, balsam, poplar, cottonwood, are suitable for wood pulp; the hard woods, such as mahogany, hemlock, |