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Rh zone is divided into an eastern humid (or Carolinian) area and a western arid (or Upper Sonoran) area. The Carolinian area extends from southern Michigan to northern Georgia and from the Atlantic coast to western Kansas, comprising Delaware, all of Maryland except the mountainous western portion, all of Ohio except the north-east corner, nearly the whole of Indiana, Illinois, Iowa and Missouri, eastern Nebraska and Kansas, south-eastern South Dakota, western central Oklahoma, northern Arkansas, middle and eastern Kentucky, middle Tennessee and the Tennessee valley in eastern Tennessee, middle Virginia and North Carolina, western West Virginia, north-eastern Alabama, northern Georgia, western South Carolina, the Connecticut Valley in Connecticut, the lower Hudson Valley and the Erie basin in New York, and narrow belts along the southern and western borders of the lower peninsula of Michigan. It is the northernmost home of the opossum, grey fox, fox squirrel, cardinal bird, Carolina wren, tufted tit, gnat catcher, summer tanager and yellow-breasted chat. The Upper Sonoran life-zone comprises south-eastern Montana, central, eastern and north-eastern Wyoming, a portion of south-western South Dakota, western Nebraska and Kansas, the western extremity of Oklahoma, north-western Texas, eastern Colorado, south-eastern New Mexico, the Snake plains in Idaho, the Columbia plains in Washington, the Malheur and Harney plains in Oregon, the Great Salt Lake and Sevier deserts in Utah, and narrow belts in California, Nevada and Arizona. Among its characteristic mammals and birds are the sage cotton-tail, black-tailed jack-rabbit, Idaho rabbit, Oregon, Utah and Townsend’s ground squirrels, sage chipmunk, five-toed kangaroo rats, pocket mice, grasshopper mice, burrowing owl, Brewer’s sparrow, Nevada sage sparrow, lazuli finch, sage thrasher, Nuttall’s poor-will, Bullock’s oriole and rough-winged swallow. The Lower Austral zone occupies the greater part of the Southern states, and is divided near the 98th meridian into an eastern humid or Austroriparian area and a western arid or Lower Sonoran area. The Austroriparian zone comprises nearly all the Gulf States as far west as the mouth of the Rio Grande, the greater part of Georgia, eastern South Carolina, North Carolina and Virginia, and extends up the lowlands of the Mississippi Valley across western Tennessee and Kentucky into southern Illinois and Indiana and across eastern and southern Arkansas and eastern Oklahoma into south-eastern Missouri and Kansas. It is the home of the southern fox-squirrel, cotton rat, rice field rat, wood rat, free-tailed bat, mocking bird, painted bunting, prothonotary Warbler, red-cockaded woodpecker, chuck will’s-widow, and the swallow-tailed and Mississippi kites. A southern portion of this zone, comprising a narrow strip along the Gulf Coast from Texas to Florida and up the Atlantic coast to South Carolina, is semi-tropical, and is the northernmost habitation of several small mammals, the alligator (Alligator mississippiensis), the ground dove, white-tailed kite, Florida screech owl and Chapman’s night-hawk. The Lower Sonoran zone comprises the most arid parts of the United States: south-western Texas, south-western Arizona and a portion of northern Arizona, southern Nevada and a large part of southern California. Some of its characteristic mammals and birds are the long-eared desert fox, four-toed kangaroo rats, Sonoran pocket mice, big-eared and tiny white-haired bats, road runner, cactus Wren, canyon wren, desert thrashers, hooded oriole, black-throated desert sparrow, Texas night-hawk and Gambel’s quail. It is the northernmost home of the armadillo, ocelot, jaguar, red and grey cats, and the spiny pocket mouse, and in southern Texas especially it is visited by several species of tropical birds. There is some resemblance to the Tropical life-zone at the south-eastern extremity of Texas, but this zone in the United States is properly restricted to southern Florida and the lower valley of the Colorado along the border of California and Arizona, and the knowledge of the latter is very imperfect. The area in Florida is too small for characteristic tropical mammals, but it has the true crocodile (Crocodilus americanus) and is the home of a few tropical birds. Most of the larger American mammals are not restricted to any one faunal zone. The bison, although now nearly extinct, formerly roamed over nearly the entire region between the Appalachian and the Rocky Mountains. The black bear and beaver were also widely distributed. The Virginia deer still ranges from Maine to the Gulf states and from the Atlantic coast to the Rocky Mountains. The grizzly bear, cougar, coyote, prairie dog and antelope are still found in several of the Western states, and the grey wolf is common in the West and in northern Minnesota, Wisconsin and Michigan.

Flora.—The Alpine flora, which is found in the United States only on the tops of those mountains which rise above the limit of trees, consists principally of a variety of plants which bloom as soon as the snow melts and for a short season make a brilliant display of colours. The flora of the Hudsonian and the Canadian zone consists largely of white and black spruce, tamarack, canoe-birch, balsam-poplar, balsam-fir, aspen and grey pine. In the Alleghanian Transition zone the chestnut, walnut, oaks and hickories of the South are interspersed among the beech, birch, hemlock and sugar maple of the North. In the Western Arid Transition zone the flora consists largely of the true sage brush (Artemisia tridentata), but some tracts are covered with forests of yellow or bull pine (Pinus ponderosa). The Pacific coast Transition zone is noted for its forests of giant

conifers, principally Douglas fir, Sitka spruce, Pacific cedar and Western hemlock. Here, too, mosses and ferns grow in profusion, and the sadal (Gaultheria shallon), thimble berry (Rubus nootkamus), salmon berry (Rubus spectabilis) and devil’s club (Fatsia horrida) are characteristic shrubs. In the Carolinian zone the tulip tree, sycamore, sweet gum, rose magnolia, short-leaf pine and sassafras find their northernmost limit. Sage brush is common to both the western arid Transition zone and the Upper Sonoran zone, but in suitable soils of the latter several grease woods (Artiplex confertifolia, A. canescens, A. nuttalli, Tetradymia canescens, Sarcobatus vermicuiatus and Grayia spinosa) are characteristic species, and on the mountain slopes are some nut pines (piñon) and junipers. The Austroriparian zone has the long-leaf and loblolly pines, magnolia and live oak on the uplands, and the bald cypress, tupelo and cane in the swamps; and in the semi-tropical Gulf strip are the cabbage palmetto and Cuban pine; here, too, Sea Island cotton and tropical fruits are successfully cultivated. The Lower Sonoran zone is noted for its cactuses, of which there is a great variety, and some of them grow to the height of trees; the mesquite is also very large, and the creosote bush, acacias, yuccas and agaves are common. The Tropical belt of southern Florida has the royal palm, coco-nut palm, banana, Jamaica dogwood, manchineel and mangrove; the Tropical belt in the lower valley of the Colorado has giant cactuses, desert acacias, palo-verdes and the Washington or fan-leaf palm. Almost all of the United States east of the 98th meridian is naturally a forest region, and forests cover the greater part of the Rocky Mountains, the Cascades, the Sierra Nevadas and the Coast Range, but throughout the belt of plains, basins and deserts west of the Rocky Mountains and on the Great Plains east of the Rocky Mountains there are few trees except along the watercourses, and the prevailing type of vegetation ranges from bunch grass to sage brush and cactuses according to the degree of aridity and the temperature. In the eastern forest region the number of species decreases somewhat from south to north, but the entire region differs from the densely forested region of the Pacific Coast Transition zone in that it is essentially a region of deciduous or hardwood forests, while the latter is essentially one of coniferous trees; it differs from the forested region of the Rocky Mountains in that the latter is not only essentially a region of coniferous trees, but one where the forests do not by any means occupy the whole area, neither do they approach in density or economic importance those of the eastern division of the country. Again, the forests of most of the eastern region embrace a variety of species, which, as a rule, are very much intermingled, and do not, unless quite exceptionally, occupy areas chiefly devoted to one species; while, on the other hand, the forests of the west—including both Rocky Mountain and Pacific coast divisions—exhibit a small number of species, considering the vast area embraced in the region; and these species, in a number of instances, are extraordinarily limited in their range, although there are cases in which one or two species have almost exclusive possession of extensive areas.

.—C. H. Merriam, Life Zones and Crop Zones of the United States, Bulletin No. 10 of the United States Department of Agriculture, Division of Biological Survey (Washington, 1898); I. C. Russell, North America (New York, 1904); W. T. Hornaday, American Natural History (New York, 1904); W. Stone and W. E. Cram, American Animals (New York, 1902); E. Coues, Key to North American Birds (Boston, 1896); Florence M. Bailey, Handbook of Birds of the Western United States (Boston, 1902); E. D. Cope, “The Crocodilians, Lizards and Snakes of North America,” in the Report of the United States National Museum for the year 1898 (Washington, 1900); L. Stejneger, “The Poisonous Snakes of North America,” ibid., 1893 (Washington, 1895).

 

Geographical Growth of the Nation.—The achievement of independence found the people of the United States owning the entire country between the Gulf and the Great Lakes excepting only Florida, as far to the west as the Mississippi; but the actual settlements were, with a few minor exceptions, confined to a strip of territory along the Atlantic shore. The depth of settlement, from the coast inland, varied greatly, ranging from what would be involved in the mere occupation of the shore for fishing purposes to a body of agricultural occupation extending back to the base of the great Atlantic chain, and averaged some 250 m.

Westward, beyond the general line of continuous settlement