XI. THE ORONOCO REGION

EXTENT. That vast portion of South America, stretching from the Cordillera of the Andes to the Atlantic, and from the Carribean Sea to the Rio Plata, presents several divisions characterised by certain physical features. From the elevated lands of the interior of the continent three sets of rivers take their origin, and after traversing huge basins, are at length emptied into the ocean in three directions, to the north, the east, and the south. The vegetable productions of the divisions have also their peculiarities, which are sufficiently distinct to authorise a separation; and assuming a designation from the principal river of each, we have the Oronoco Region, the Amazon Region, and the Paraguay Region, the boundaries of which are conveniently traced along the ridges of those secondary mountains, at the bases of which their tributaries have their origin.

The Oronoco Region occupies the northern part of South America, and a line running along the sierra of Araray, and traversing the continent to the Bay of Guayaquil, forms its southern limit; whilst to the north it ceases at the Gulf of St. Michael, and is elsewhere inclosed by the Atlantic and Pacific Oceans.

PHYSICAL CHARACTERS.-Some lesser ranges of mountains traverse the region, with their sides broken into steep and confined valleys. From their bases extend vast plains or llanos, covered either with forest or luxuriant grasses. These extensive llanos are represented in Brazil by the campos, and around Buenos Ayres by the pampas, but are here in their greatest richness. The rivers often inundate their banks, fertilizing a soil already extremely rich, and for a time

converting large districts into savannah. A very sandy soil prevails in some places, as in the neighbourhood of Cumana, supporting chiefly multitudes of gigantic cacteæ. Humboldt has observed that the vegetation here appeared more luxuriant wherever the limestone was covered by quartzy sandstone, the latter appearing favourable to the retention of moisture.

CLIMATE.-Situated so near the equator, the climate is a warm one. Caraccas has an annual mean of from 70° to 72°, which, however, is far too low for the region, perhaps as much as 8°. The range is stated to be from 51° to 85°, being considerable for the latitude. The humidity of the atmosphere varies according to the soil and vegetation. On the Pacific, in the Bay of Choco, rain falls ten months in the year, but in the more arid parts rain is far from frequent or abundant. The climate of Guiana has been supposed to be favourable to the growth of certain spices, as cloves and nutmegs, which, from some idiosyncracy, are still produced of the best quality only in the Moluccas.

FLORA.-Much of the region is covered with forest, particularly in the vicinity of the oceans, between which and the interior a broad belt intervenes. In many instances the trees are remarkable for the beauty of their wood, the fragrance of their secretions, and the rich and valuable resins they exude. In Guiana trees of this character are very numerous, and belong chiefly to Laurineæ. Throughout are spread a vast number of representatives of the tropical arborescent families. Gramineæ abound in the llanos, chiefly of kellingia, cenchrus, and paspalum, intermixed with species of mimosa, turnera, and malvaceæ. On some of the rivers a grass, cynerium saccharoides, attains a height of thirty-two feet. Where the climate is humid, piperaceæ, passifloreæ, and me

lastomaceæ, are very numerous, overshadowed by the singular clusia and the lofty and fecund bignonia. Filices are numerous as individuals, but, together with orchidaceae, do not abound in species. Some palmæ are peculiar, and of interest.

RELATIONS.-With the neighbouring regions there are naturally some strong affinities. Rhopala, a proteaceous genus, occurs; and also a species of punica.

XII. THE ANDES REGION.

EXTENT.-As ur alpine regions always commence at the line which separates the cultivation of the lowlands from that of the mountains, the lower boundary will be at 6,500 feet, and includes all above this to the confines of the vegetable world at 18,000 feet. It stretches to the northward along the magnificent mountain chains of New Granada, and to the south through Peru and Bolivia, where the line of lowland cultivation will descend a little. Its exact extent to the south has not been acertained.

PHYSICAL CHARACTERS.-Among the stupendous scenery of the Andes and the steep and scarped precipices and mountain sides, vegetation would appear unlikely to flourish; yet these often afford a shelter, and also assist to collect a soil in the valleys and plains. Hence, from the barrenness of a bare surface of primitive rocks, to the luxuriance of fertile and warm valleys, there is every variety of productiveness. In the plains between parallel ranges the soil is often deep and rich, and is equally suited to agriculture or the rearing of herds of cattle. Mountain torrents descend in fury through deep chasms,

or sometimes assuming, for a while, tranquillity, wander in peaceful and fertilizing streams through the plains.

CLIMATE. The atmosphere of alpine regions is liable to violent disturbance from storms, which are both rapid in their approach and disappearance, and often leave behind much devastation among the trees of the forest. The temperature of any given spot is very equable, and ranges, for the whole region, from 65° to several degrees below the freezing point. Rain falls throughout the year in frequent showers, with little regard to the seasons, and the amount is no where great. To the decreased pressure, greater brilliancy of the sun's rays, and diminished suspended moisture, some of the peculiarities may be referred.

FLORA. The least elevated portion is occupied by a magnificent forest, and valuable as containing numerous species of cinchona, which yield a medicine highly prized throughout the world, except in the neighbourhood of its production. Some tropical families ascend tenaciously to these elevations, as piperaceæ, melastomaceæ, cacteæ, and passifloreæ, the latter assuming the novel habit of arborescence; and the numerous synanthereæ are particularly characteristic. Ficus, oreocallis, clusia, persea, and ocotea, are mingled with podocarpus, quercus, ilex, and salix. Above the forest is a large district of bushes with much variety in the species; drymis and wintera from the south, meet ribes, rubus, and viburnum from the north, and are associated with various species of thibaudia, alnus, andromeda, fuchsia, vaccinium, calceolaria, culcitium, duranta, barnardesia, escallonia, berberis, and befaria. The flora is agreeably diversified by some hæmanthus, alstromeria, sisyrinchium, and other liliaceous plants. The grasses, which, in both a botanical and economical point of view, are so important, occupy a broad space between 13,000

and 14,500 feet, and are contributed chiefly by jurava, stipa, agrostis, panicum, avena, and dactylis. Succeeding to the grasses are many herbaceous plants, and lastly the lichens, crowning, as it were, the flora of the region. Even this very slight sketch would be incomplete without mentioning some of the groups which flourish on the higher elevations and give an aspect of variety. A few of these are herbaceous compositæ, lowly umbelliferæ, saxifrageæ, cruciferæ, valerianeæ, and caryophylleæ ; with species of gentiana, rumex, plantago, arum, oxalis, dorstenia, swertia, and lobelia. The plants attaining the greatest elevation are two lichens, umbilicaria pustulata and verrucaria geographica.

RELATIONS.-Between all alpine regions there will be numerous analogies, but few points of identity, and also a certain similarity with regions of the lowlands in a proportionate latitude. With the Mexico alpine region are several sources of resemblance through ericaceæ, synanthereæ, cruciferæ, quercus, salix, and cheirostemon platanoides. It however is deficient in the important genera of pinus, abies, and rosa. The flora is so rich and varied, that relations may easily be traced with most regions under a temperate climate.

XIII. THE AMAZON REGION.

EXTENT. This extensive region occupies a chief part of the empire of Brazil, and comprises the richest and finest portion of South America. It consists of a magnificent basin intersected by a multitude of rivers, many of which are of considerable size. The original streams of the largest of these, the Amazon, have their rise in the Andes, and gradually uniting their waters, traverse the region to the Atlantic ocean. Its boundaries are the