1911 Encyclopædia Britannica/Sisal Hemp

SISAL HEMP, or Henequen, of Florida and the Bahamas, the product of Agave rigida, variety sisalana, a native of Yucatan, but found in other parts of Central America and distributed to the West Indies, where it is being increasingly cultivated.

Agave (q.v.) is a member of the order Amaryllidaceae; and a well-known species of the genus, Agave americana, the century plant, will suggest the habit of the sisal hemp, which, however, differs in the absence of prickles along the margin of the fleshy leaf. After six or seven years the flowering stalk or “pole” develops from the centre of the leaf-cluster, and grows to the height of 15 or 20 ft. The flowers are borne in dense clusters at the ends of short lateral branches, and closely resemble those of Agave americana. After they have begun to wither, buds are developed from the point of union with the flower-stalk; these form tiny plants, which, when several inches long, become detached and fall to the ground. Those that fall in a suitable place take root and are soon large enough to transplant. After flowering the plant perishes, but is renewed by suckers springing from the base of the stem; these suckers are then planted, and the leaves should be ready for cutting in about four years. The other method of planting is by means of “pole” plants just described.

In collecting the fibre the leaves are cut off at the base, the spine at the top end removed, and the leaves carried in bundles to the machines. Here two scraping wheels remove the pulp from the leaves. The leaves are put into the machine at one side, and delivered clean at the other. One half is cleaned by the first wheel, then the cleaned portion is held while the second wheel cleans the remainder of the leaf; all the operations are automatically performed. In Yucatan, the leaves measure from 4 to 5 ft. in length, about 4 in. in width, and ½ in. in thickness. They are lance-shaped and weigh from 1½ ℔ to 1¾ ℔ on an average. As only about 3 to 4% of the weight is available for fibre, the average yield of 1000 leaves is from 50 to 60 ℔. The yield per acre is estimated at about half a ton. It has been proposed to treat the pulp, &c., with a view to extracting the chemical substances, but we are not aware that any successful attempt has been made. The fibre is yellowish-white, straight, smooth and clean, and a valuable cordage fibre second only to manila fibre in strength. It is used extensively for cordage and binder twine, both alone and in conjunction with manila, and is also used for bags, hammocks and similar articles.

The plants thrive on arid rocky land, growing, for instance, on the Florida Keys upon the almost naked coral rock. Their northern limit of cultivation is determined by frost, which the plants will not stand; in Florida this is represented by the line of 27° N. An inferior fibre is obtained from the leaves of another species, Agave decipiens, which is found wild along the coasts and keys of Florida. It is known as the false sisal hemp, and can at once be distinguished from true sisal by its spiny leaf-margin.

SISKIN (Dan. sidsken, Ger. Zeisig and Zeising), long known in England as a cage-bird called by dealers the Aberdévine or Abadavine, names of unknown origin, the Fringilla spinus of Linnaeus, and Carduelis spinus of modern writers, belongs to the Passerine family Fringillidae. In some of its structural characters it is most nearly allied to the goldfinch (q.v.), and both are placed in the same genus by systematists; but in its style of coloration, and still more in its habits;, it resembles the redpolls (cf. Linnet), though without their slender figure, being indeed rather short and stout of build. Yet it hardly yields to them in activity or in the grace of its actions, as it seeks its food from the catkins of the alder or birch, regardless of the attitude it assumes while so doing. Of an olive-green above, deeply tinted in some parts with black and in others lightened by yellow, and beneath of a yellowish-white again marked with black, the male of this species has at least a becoming if not a brilliant garb, and possesses a song that is not unmelodious, though the resemblance of some of its notes to the running-down of a piece of clockwork is more remarkable than pleasing. The hen is still more soberly attired; but it is perhaps the siskin's disposition to familiarity that makes it so favourite a captive, and, though as a cage-bird it is not ordinarily long-lived, it readily adapts itself to the loss of liberty. Moreover, if anything like the needful accommodation be afforded, it will build a nest and therein lay its eggs; but it rarely succeeds in bringing up its young in confinement. As a wild bird it breeds constantly, though locally, throughout the greater part of Scotland, and has frequently done so in England, but more rarely in Ireland. The greater portion, however, of the numerous bands which visit the British Islands in autumn and winter doubtless come from the Continent—perhaps even from far to the eastward, since its range stretches across Asia to Japan, in which country it is as favourite a cage-bird as with us. The nest of the siskin is very like that of the goldfinch, but seldom so neatly built; the eggs, except in their smaller size, much resemble those of the greenfinch (q.v.).

A larger and more brightly coloured species, C. spinoides, inhabits the Himalayas, but the siskin has many other relatives belonging to the New World, and in them serious modifications of structure, especially in the form of the bill, occur. Some of these relatives lead almost insensibly to the greenfinch (ut supra) and its allies, others to the goldfinch (ut supra), the redpolls and so on. Thus the siskin perhaps may be regarded as one of the less modified descendants of a stock whence such forms as those just mentioned have sprung. Its striated plumage also favours this view, as an evidence of permanent immaturity or generalization of form, since striped feathers are so often the earliest clothing of many of these birds, which only get rid of them at their first moult. On this theory the yellowbird or North-American “goldfinch,” C. tristis, would seem, with its immediate allies, to rank among the highest forms of the group, and the pine-goldfinch, C. pinus, of the same country, to be one of the