The bark of B. ficempferi is also used for similar purposes in Japan.
Butea frondosa, and B. bark and roots of both species yield a fibre which is locally used for cordage. The trees are, however, much more important as affording a valuable rosin (see Resinous Substanees—Butea kino). They also afford a dye (see Dye-stuffs—Kisso).
Calotropis or ; shrub, ft. high. This plant is extremely common all over S. India, growing in waste places, and among rubbish and ruins, and often even encroaching upon cultivated ground, as a troublesome weed. It comes to maturity in a year, but is perennial, and, when once planted or sown, requires no further care. It thrives on soils where nothing else will grow, and needs neither culture nor water ; hence it is admirably adapted for bringin'g waste land under tillage, and for protecting reclaimed desert from drifting sands. These reasons alone should suffice to encourage the cultivation of the plant, apart from its value as a fibre-producer. Its great abundance, in a wild state, may render cultivation unnecessary for a time. It is stated that an acre stocked with plants 4 ft. apart each way, will yield 10 tons of green stems, or 582 lb. of fibre, as prepared by the present native process, which wastes 25 per cent.; the cost of cultivation of the same area is placed at 21. 9s. 8d., after which, the only recurring expendi ture would be for harvesting the plant. When raised from seed, it is said by some to require two years before being ready for cutting ; but if cut close to the ground, it grows again rapidly, yielding a second crop within 12 months from the first.
The fibres afforded by the plant are of two distinct kinds :—(1) The seeds are coated with silky hairs, forming one of the so-called "vegetable silks," used occasionally for stuffing purposes, and said to be sometimes woven into shawls and handkerchiefs, and to form good paper-stock ; (2) the stems contain a bast fibre, of great industrial value, The following remarks refer only to the latter. The native method of extracting the fibre is as follows :—The straightest branches, 12-18 in. long, are cut, and allowed to wither for at least 24 hours ; after 2-3 days, the dried stems are gently beaten, especially at the joints, which permits the bark, and the fibre attached, to be peeled off, without breaking. The bark is then bitten through in the centre, and the fibre is drawn away
from it, and dried in the sun. The process is necessarily very expensite, the cost of the fibre being estimated at 65/. a ton. Retting, it seems, cannot be adopted, as the fibre is discoloured and injured by it, owing to the solution of an acrid juice contained in the plant. The lack of a cheap, efficient machine for extracting the fibre appears to be the only obstacle to its extended use ; yet little seems to have been done in the way of trying existing machines, or inventing new ones. Mr. Strettell's observations on this head are disappointingly meagre ; his idea, that the machine used for dressing dry agave fibre (see p. 913-6) might be suitable, appears reasonable.
The fibre is said to possess many of the qualities of flax (Linum usitatissimum), though it is some what finer. Its fineness, tenacity, lustre, and softness, fit it for many industrial purposes. In Madras, the natives select it as the strongest material for bowstrings, gins, and tiger-traps ; never theless, it is said to be better adapted for textiles than for cordage, and that it may readily be mixed with silk. Yet it shows a high degree of resistance to moisture ; samples, exposed for 2 hours to steam at 2 atmos., boiled in water for 3 hours, and again steamed for 4 hours, lost only per cent. by weight, as compared with flax, 3.50 ; Manilla hemp, 6.07; hemp, ; coir, 8•13. The strength of the fibre is also considerable ; according to Dr. Wight, it is the strongest fibre of the Madras side of India, bearing 552 lb., as compared with the next strongest, Sunn hemp (Crotalaria juncea), 407 lb.; and in Dr. Royle's experiments, it sustained 190 lb., as again-t Russian hemp, 160 lb. It can be spun into the finest thread, and has been pronounced equal to good flax, for making prime yarns. It is also said to possess all the qualities requisite to produce a compact felted first-class paper.