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belt and giving up its store of vapour, flows off north and south as dry, cool air, and descends to the earth in the vicinity of the tropics. Here it sucks up whatever moisture it meets with and thus tends to keep this zone in an arid condition. The trades themselves are believed to be supplied by descending currents from the temperate zones, and these are at first equally dry and only become vapour-laden when they have passed over some extent of moist surface. At the solstices the sun passes vertically over the vicinity of the tropics for several weeks, and this further aggravates the aridity ; and wherever the soil is sandy and there are no lofty mountain-chains to supply ample irrigation the result is a more or less perfect desert. Analogous causes, which a study of aerial currents will render intelligible, have produced other great forest-belts in the northern and southern parts of the temperate zones; but owing to the paucity of land in the southern hemisphere these are best scen in North America and Northern Euro-Asia, where they form the great northern forests of deciduous trees and of Conifera. These being comparatively wellknown tu iis, will form the standard by a reference to which we shall endeavour to point out and render intelligible the distinctive characteristics of the equatorial forest vegetation.
General Features of the Equatorial Forests. It is not casy to fix upon the most distinctive features of these virgin forests, which nevertheless impress themselves upon the beholder as something quite unlike those of temperate lands, and as possessing a grandeur and sublimity altogether their own. Amid the countless modifications in detail which these forests present, we shall endeavour
species, while fine string of excellent quality used even for bow-strings, fishing-lines, and hammocks, is made of fibres obtained from the unopened leaves of some American species. The fibrous sheath at the base of the leaves of the cocoa-nut palm is so compact and cloth-like, that it is used for a variety of purposes, as for strainers, for wrappers, and to make very good hats. The great woody spathes of the larger palms serve as natural baskets, as cradles, or even as cooking-vessels in which water may be safely boiled. The trunks form excellent posts and fencing, and when split make good flooring. Some species are used for bows, others for blow-pipes ; the smaller species are sometimes used as needles or to make fish-hooks, and the larger as arrows. To describe in detail all the uses to which palm-trees and their products are applied in various parts of the world might occupy a volume; but the preceding sketch will serve to give an idea of how important a part is filled by this noble family of plants, whether we regard them as a portion of the beautiful vegetation of the tropics, or in relation to the manners and customs, the lives and the well-being of the indigenous inhabitants.
Ferns.--The type of plants which, next to palms, most attracts attention in the equatorial zone, is perhaps that of the ferns, which here display themselves in vast profusion and variety. They grow abundantly on rocks and on decaying trees; they clothe the sides of ravines and the margins of streams ; they climb up
the trees and over bushes; they form tufts and hanging festoons among the highest branches. Some are as small as mosses, others have huge fronds eight or ten feet long, while in mountainous districts the most elegant of the gronp, the
tree-ferns, bear their graceful crowns on slender stems twenty to thirty, or even fifty feet high. It is this immense variety rather than any special features that characterises the fern-vegetation of the tropics. We have here almost every conceivable modification of size, form of fronds, position of spores, and habit of growth, in plants that still remain unmistakably ferns. Many climb over shrubs and bushes in a most clegant manner; others cling closely to the bark of trees like ivy. The great birds'-nest fern (Platycerium) aitaches its shell-like fronds high up on the trunks of lofty trees. Many small terrestrial species have digitate, or ovate, or ivyshaped, or even whorled fronds, resembling at first sight those of some herbaceous flowering plants. Their numbers may be judged from the fact that in the vicinity of Tarrapoto, in Peru, Dr. Spruce gathered 250 species of ferns, while the single volcanic mountains of Pangerango in Java (10,000 feet high) is said to have produced 300 species.
Ginger-worts and wild Bananas.—These plants, forming the families Zingiberacea and Musaccæ of botanists, are very conspicuous ornaments of the equatorial forests, on account of their large size, fine foliage, and handsome flowers. The bananas and plantains are well known as among the most luxuriant and beautiful productions of the tropics. Many species occur wild in the forests ; all have majestic foliage and handsome flowers, while some produce edible fruit. Of the ginger-worts (Zingiberaceæ and Marantaceæ), the well known capnas of our tropical gardens may be taken as representatives, but the equatorial species are very numerous and varied, often forming dense thickets in damp places, and adorning the
forest shades with their elegant and curious or showy flowers. The maranths produce “arrow-root," while the ginger-worts are highly aromatic, producing ginger, cardamums, grains of paradise, turmeric and several medicinal drugs. The Musaccæ produce the most valuable of tropical fruits and foods. The banana is the variety which is always eaten as a fruit, having a delicate aromatic flavour; the plantain is a larger variety which is best cooked. Roasted in the green state it is an
state it is an excellent vegetable resembling roasted chestnuts; when ripe it is sometimes pulped and boiled with water, making a very agreeable sweet soup; or it is roasted, or cut into slices and fried, in either form being a delicious tropical substitute for fruit pudding. These plants are annuals, producing one immense bunch of fruit. This bunch is sometimes four or five feet long containing near 200 plantains, and often weighs about a hundredweight. They grow very close together, and Humboldt calculated that an acre of plantains would supply more food than could be obtained from the same extent of ground by any other known plant. Well may it be said that the plantain is the glory of the tropics, and well was the species named by Linnæus-Jusa paradisiaca !
Arums.--Another very characteristic and remarkable group of tropical plants are the cpiphytal and climbing
These are known by their large, arrow-shaped, clark
green and glossy leaves, often curiously lobed or incised, and sometimes reticulated with large open spaces, as if pieces had been regularly caten out of them by some voracious insects. Sometimes they form clusters of foliage on living or dead trees to which they cling by their acrial roots. Others climb up the smooth
bark of large trees, sending out roots as they ascend which clasp around the trunk. Some mount straight up, others wind round the supporting trunks, and their large, handsome, and often highly-remarkable leaves, which spread out profusely all along the stem, render them one of the most striking forms of vegetation which adorn the damper and more luxuriant parts of the tropical forests of both hemispheres.
Screw-pines.—These singular plants, constituting the family Pandanaces of botanists, are very abundant in many parts of the Eastern tropies, while they are comparatively scarce in America. They somewhat resemble Yuccas, but have larger leaves which grow in a close spiral screw on the stem. Some are large and palm-like, and it is a curious sight to stand under these and look up at the huge vegetable screw formed by the bases of the long drooping leaves. Some have slender-branched trunks, which send out acrial roots; others are stemless, consisting of an immense spiral cluster of stiff leaves ten or twelve feet long and only two or three inches wide. They abound most in sandy islands, while the larger species grow in swampy forests. Their large-clustered fruits, something like pineapples, are often of a red colour ; and their long stiff leaves are of great use for covering boxes and for many other domestic uses.
Orchids. These interesting plants, so well known from the ardour with which they are cultivated on account of their beautiful and singular flowers, are preeminently tropical, and are probably more abundant in the mountains of the equatorial zone than in any
other region. Ilere they are almost omnipresent in some of their countless forms. They grow on the stems, in the