FLORA. North America.—Tho flora of North America is varied, ranging from those plants peeuliar to Arctic regions to those of the tropics. In the extreme northern part of Canada and Alaska, whore 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 Can ada, 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 heavi est forests in the world, consisting entirely of conifer:', great firs, sugar pines. redwoods, and the giant sequoia, the largest and the oldest liv ing thing.
Eastern Canada and the United States are forested, the western limit including most of Min nesota, Wisconsin, and Indiana, southern Mis souri, 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 Cor dilleran plateau.
In the Cerdilleran region forests are, as a rule, found only on the mountains, and consist mainly of conifers'. The valley vegetation de pends 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 chap arral. 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
AlorNTAINS: ('.XNADA ; STATES; :MEXICO; NICARAGUA, etc.
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. .1t 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 conifers' higher on the moun tains. 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 Alatto 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 re gions, is in general tropical or sub-tropical at low levels, and changes in attitudinal 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 rain fall. The potato is indigenous to South America. See Flora under ANDES; COLOMBIA; ECUADOR; PERU; BOLIVIA; CUILE; A.MAZON; BRAZIL, alld ARGENTINA.