H.—These sections may also be examined under reagents, in which case, they are not macerated in dilute glycerine, but in alcohol, in order to eliminate any resinous matters they may contain. They are then dried, before the treatment with iodine.
The foregoing tests are intended for distinguishing the fibres of one plant from those of another. They will be repeatedly referred to in subsequent portions of this article. To discriminate between vegetable fibres and animal fibres (see Hair, Silk, Wool) the following observations will suffice : Vegetable fibres, heated in solutions of alkalies or acids, swell up, dissolve, and decompose into glucose or grape sugar. They burn readily, and with a flash.
Animal fibres, boiled in solutions of caustic alkalies, swell-up, dissolve, and decomposq with evolution of ammonia. They carbonize with difficulty, and only on continued application of heat, and emit an odour like burning horn or feathers.
A ready method of estimating the proportion of fibre (celinloae) yielded by a plant, is to macerate it, for some hours, in water ; crush it, by passing it between wooden rollers ; subject it to the action of a weak (6 per cent.) solution of carbonate of soda, and then to steam at a pressure of 4-5 atoms., until the cellulose is extracted as a yellowish-brown mass. This is a preliminary teat of the value of a plant for paper-making (see Paper). Several other methods are described by Bevan and Cross, in their paper mentioned in the Bibliography at the end of this article.
Fig. 625 shows an apparatus for determining the resistance, elasticity, and torsion, of fibrous threads. The clasps n receive the ends of the thread ; they may be twisted or untwisted at will, and be moved either towards or from each other ; H R is a graduated dial-plate, the needles of which indicate the number of turns per unit of length ; D is a dynamometer, with a needle L, movable under the influence of the traction ; p, a constant weight ; M, the handle by which the traction is exerted upon the thread.
Having treated of vegetable fibres generally, it now remains to enumerate such as are already known, and to point out where they will grow, how they are prepared, and to what purposes they are or may be applied.
Abroma perennial ; small tree. A doubtful native of the interior of the Indian peninsula, flourishing in gardens up to 30° N. lat., and eastwards to the Philippines. Grows well and quickly, and yields 2-4 crops yearly of bark fit for peeling ; 3 trial cuttings gave 271 lb. of clean fibre. The bark is separated from the shoots by maceration in stagnant water for 4-8 days in summer ; in the cold season, a three times longer steeping is necessary, and greatly weakens the fibres. The latter are naturally white and clean, and require no dressing; they are about stronger than Crotalaria juncea (Suns hemp)—say 74 lb. : 68 lb.—and are much more durable in water. Used locally, as substitute for hemp, in cordage ; equal to jute for paper-making.
Abutilon Avicennas [Sida Abutilon] — American ; herbaceous annual. Now become a troublesome and hardy weed of the Middle States of America. The plant is being recommended for cultivation, as yielding a fibre which may be applied to all the purposes for which jute is now so largely imported into America. The seed is to be sown broadcast on rich soil, and to receive plenty of manure, when the yield is confidently expected to bo 4-7 tons of dry stalks to the aere.
A. indicum. [Sida indica, S. in most parts of India, and in Burmah. Stem yields a strongish fibre, fit for rope-making, and occasionally applied to that purpose in the Bancoorah district.
A. oxycarpum is a shrub of various parts of New South Wales, Queensland, W. and N. Australia ; yields a textile fibre. A. polyandrum on the Nilgiri Hills, and about Nundidroog ; yields a long, silky, hemp-like fibre, suited for ropes. The fibres of A. venosum, A. amplum, A. auritum, A.
A. striatum, are utilized in S. Africa, Brazil, Australia, and the E. Indies. In Algeria, A. indicum is extensively cultivated.
Acacia ; tree. Found in Sholapore, on the Coromandel coast, in Ceylon and in Burmah. The bark is macerated for 4-5 days, and beaten ; it yields a tough, strong fibre, used locally for making large fishing-nets and coarse cordage.