range receives little moisture. Farther south, in southern Chile and Argentina, the conditions are reversed. The westerly winds bring rain to the narrow strip of land on the west coast, which receives as much as 80 inches in certain localities, and the pampas on the east receive very little, on account of the intercepting mountains.
Flora. North America.—The flora of North America is varied, ranging from those plants peculiar to Arctic regions to those of the tropics. In the extreme northern part of Canada and Alaska, where the ground is constantly frozen, thawing only on the surface in the summer, and forming the well known tundra, the prevailing plant life consists of reindeer moss, with a few dwarf Arctic willows. But in the short, hot summers of this region even the tundra is gay with bright-colored blossoms. Near the Arctic Circle forests of spruce, with some birch and alders, appear, at first in scattering clumps, then more continuously. Thence southward as far as the North Saskatchewan River, in Canada, the land is forested with coniferous trees, spruce, pine, fir, and hemlock. This timbered area extends southward along the Pacific coast nearly to San Francisco Bay. In Washington, Oregon, and California exist probably the heaviest forests in the world, consisting entirely of coniferæ, great firs, sugar pines, redwoods, and the giant sequoia, the largest and the oldest living thing.
Eastern Canada and the United States are forested, the western limit including most of Minnesota, Wisconsin, and Indiana, southern Missouri, the eastern part of Indian Territory, and northeastern Texas. In the central United States, the prevalent species change to hard woods, while in the Southern States yellow pine becomes the dominant species. West of this forested region in the United States and Canada is the prairie region, once grassed, and with groves of timber, now highly cultivated, which passes by insensible degrees into the treeless plains which form the eastern slope of the Cordilleran plateau.
In the Cordilleran region forests are, as a rule, found only on the mountains, and consist mainly of coniferæ. The valley vegetation depends upon the degree of aridity; here may be found grass, artemisia, cacti, yucca, and other thorny desert shrubs, which in some localities grow so densely as to form what is called chaparral. The northern plateau region of Mexico is without forests, except upon the higher ranges, while the southern and lower part of the country, with Central America, has a tropical profusion of fruit and vegetation. See Flora under Rocky Mountains; Canada; United States; Mexico; Nicaragua, etc.
South America.—The flora of South America ranges from that of the tropical to that of the temperate zone, and is controlled not only by latitude, but by altitude and rainfall. At the extreme north in Colombia, on the waters of the Magdalena, the hot climate and excessive rainfall produce a luxuriant vegetation which changes from its tropical character only with great change of altitude above the sea, palms, bamboos, and tree ferns forming much of the lower forests, and coniferæ higher on the mountains. To the east of this region are the llanos of the Orinoco, with their tall grasses and iso- lated trees. To the south of these, east of the Andes, are the great selvas of the Amazon, with their rich forests and mixed flora. Directly south of these occur the great forests of the Matto Grosso, to the east of which lie the Catinga woodlands and the Brazilian campos, with their thickets interspersed with open glades. To the west of the Matto Grosso lies the great mountain of southwestern Brazil and Bolivia. To the south of the Matto Grosso lies the Gran Chaco, with its wax palms and other rich forest growth. Still farther south begins the plains or pampas of the Plata, which, at first consisting of rich grasses, soon degenerate into the dry plains of southern Argentina, with their stunted and poor plant growth. The flora of the western strip of South America, which includes the Andean regions, is in general tropical or sub-tropical at low levels, and changes in altitudinal zones with increase of height above the sea level, but is much modified by the distribution of rainfall throughout the length of the continent, which permits of an abundant vegetable growth in the northern and southern portions, but greatly limits it in the intervening region of little rainfall. The potato is indigenous to South America. See Flora under Andes; Colombia; Ecuador; Peru; Bolivia; Chile; Amazon; Brazil, and Argentina.
Fauna. In considering this subject, it must be recognized first that we here have to deal with two continental faunæ, for the animal life of North America is almost completely different from that of South and Central America. This unlikeness seems related in large degree to history and derivation. The fauna of North America is very similar to that of the northern zones of the Old World, in large part identical with it. Among mammals substantially similar to those of Europe or northern Asia are all the bears, wolves, the lynx, most fur-bearers (Mustelidæ), the bison, reindeer, moose (“elk” of Europe), bighorn, white goat, beaver, and the majority of the rodents and small insectivores, bats, etc., where the differences are rarely more than generic. The peculiar North American mammals of note are the puma, the skunk, the pronghorn, the musk-ox, and certain rodents, as the pouched-rats and sewellel. The absentees are equally interesting. Although they arose in Tertiary North America, no horses, camels, or rhinoceroses are in its recent fauna; nor any true antelopes or swine (except in the extreme southwest); of Marsupials a single form, the opossum, is present. The birds present a similar parallelism with northern Europe and Asia, many species, and nearly all the families, being common to both continents. The same is true of reptiles and amphibians, which are marked in North America by the preponderance of certain subordinate forms, such as the rattlesnakes, rather than by anything very different from those of the Old World. Fishes present somewhat greater distinctions, yet the bulk of fresh-water fish are similar to, and some are identical with, those of the colder parts of Europe. Insects and fresh-water mollusks seem generally related to those of Europe and Asia; but the United States is richer than any other part of the world in fluviatile mollusks—especially river mussels (Unionidæ) . On the whole, the Nearctic fauna is closely allied to the Palæarctic, and by some students they are united in
