FOREST TREES, Tropical. Most
interesting trees grow between the tropics, some of
which have traveled quite around the globe. A
vast number of economic products, exclusive of
the more important tropical fruits, derived from
them, have been carried far and wide since the
dawn of commerce. The character of these
forests varies greatly, influenced by waterfall
and altitude. This is illustrated in Porto Rico
where “the various formations in the order of
their occurrence from the coast toward the
interior are as follows: Littoral woodlands, moist deciduous forests, and tropical rainforests on the north or humid side, and the dry deciduous forest on the south or semi-arid side.” These different formations overlap more or less, or disappear but are to be recognized everywhere in the tropics.
The most obvious difference lies between
those trees growing on hot dry areas like the
Liguanea plain in Jamaica, where rain falls
perhaps twice a year and then in torrents, and
those forming dense forests on the nearby
mountains, where rain and fogs are frequent. In dry soil the trees grow sparsely, and are apt to be low and broad of head, with foliage subdivided, and sometimes armed with thorns. The leguminous tribe is usually well represented. In the jungle, however, the arborescent growth is more interesting to the eye. The foliage is often evergreen, thick and glossy with waxen coatings designed to shed water, and simple of outline. In the heat and moisture of these damp deciduous and tropical rain forests, as Colonel Roosevelt remarks, “The struggle for life among the forest trees and plants is far more intense than in the North. The trees stand close together, tall and straight, and most of them without branches, until a great height has been reached; for they are all striving toward the sun, and to reach it they must devote all their energies to producing a stem which will thrust its crown of leaves out of the gloom below into the riotous sunlight which bathes the billowy green upper plane of the forest.” The trunks of these trees are usually pale gray or pallid in hue, and many of them have brilliant flowers such as those crowning the bois immortelle, which are, however, unsuspected by the stroller beneath, unless the forest floor be littered with gay petals fallen from their place under the sun, where only an aeronaut or mountain climber can see them. Huge vines or lianes, which rise upward with the trees that they embrace, are characteristic of these forests; some are as straight and thick as saplings, others are twisted and contorted; others cling inseparably to the boles. Some clothe the tree-trunks with verdure, others hang naked like ropes dangling from a ship's rigging. The trees are moreover loaded with masses of epiphytic plants, ferns and mosses. Orchids form huge tufts, or trail in long flowering streamers, and stiff wild pines hold water in the cup-like bases of their leaves in which little batrachians bathe. These features are most easily seen at the edges of clearings laboriously hacked out with cutlass or machete for garden patches. Tropical forests are continuously destroyed and steep hills left bare for the action of erosive forces, by these small cultivators who supply most of the constant supply of green-stuff used in towns. They cut down the giant trees with all their burdens and either consume them in charcoal kilns or in huge bonfires that are a characteristic sight among the mountains,
burning like beacons night and day, and often
burning over more territory than is required. The ashes supply fertilizer, and when the ground is exhausted in a few years the gardeners repeat the process.