North America

The analogy of a tropical hurricane to a tornado has already been referred to, but while a tornado may lay waste a tract of country perhaps half a mile wide, and in exceptional cases 20 to 30 miles in length, a hurricane is from 200 to 300 miles in diameter, and may continue to be destructive, on account of the rapid inflow of air from the periphery towards the centre, for 2,000 or 3,000 miles. The velocity of the spirally blowing winds which are the characteristic feature of these great storms is frequently 100 miles or more per hour. In spite of their magnitude, however, the conditions leading to their origin and growth are essentially the same as in the case of tornadoes, and even of the much smaller whirlwinds. They have their birth where the moist, still air above the ocean in the region of the doldrums at the season when the equatorial belt of calms is farthest north, becomes highly heated and rises on account of the pressing in of cooler and heavier air from adjacent regions. The ascending column is at first carried slowly westward, in obedience to the general flow of the atmosphere in the intertropical belt, and at the same time the currents coming in from opposite directions give the ascending air a rotary motion. As the currents from the northeast are stronger than those from other directions, this whirling motion is from right to left, or opposite to the movement of the hands of a watch. The whirling air column extends into the upper atmosphere, and as it moves along past the West Indies becomes influenced by the prevalent flow of the upper air-currents, and is carried northwestward, and later eastward in a path which approximates to a parabolic curve. The inward-rushing spiral winds leave a calm centre, the "eye of the storm," which corresponds to the hollow core of a whirlwind and the calm centre sometimes noted in tornadoes. The upward ascent of warm, humid air is accompanied by a decrease of pressure and consequent expansion and cooling which leads to rapid condensation and a heavy downpour of rain; the change of the moisture from a vaporous to a liquid form liberates heat, which serves to perpetuate the upward flow of air, and thus prolongs the life of the storm. During the passage of the central area of low barometric pressure over a given locality the clouds frequently part and portions of the clear sky may be seen. Accompanying the rain are frequent lightning flashes, as during ordinary thunder-storms.

The tropical hurricanes are the most violent and most dreaded of all the storms that sweep over any portion of our continent, but fortunately for dwellers on the land, are confined for the most part to the sea, since the atmospheric conditions over the land lead to their loss of energy, although in rare instances they may be re-enforced by uniting with a cyclonic storm, as happened in the case of the Galveston hurricane, and thus continued after reaching the land. The destructiveness of the hurricanes at sea has been greatly lessened in recent years, not only on account of the general use of steam as a motive power for vessels instead of the wind, but because meteorologists can designate the time when they are likely to occur and the best method of sailing away from them if encountered. Since the establishment of the United States stations for observing and reporting the atmospheric conditions on the West India islands, the approach of a hurricane can be foretold and warning given to navigators and others of the coming danger.

An important element in climate is the amount of moisture the air contains. The absolute amount of water vapour in a given volume of air is of interest in this connection, but what is of still greater importance is the ratio of the amount of water vapour present to that which the air might contain, or what is termed the relative humidity. The relative humidity, providing the actual amount of vapour present remains unchanged, depends upon the temperature of the atmosphere. For this reason, the warming of an air-current, as the trade-winds, for example, in which the water vapour present may, previous to the warming, have approached saturation, causes it to have a still greater capacity, and hence decreases the relative humidity.

The winds in passing over the land may be either cooled or warmed, and hence their influence on evaporation is continually changing; but the mean rate of evaporation from an open water body can be determined for a definite time, say a year, for various localities, and thus afford a means of comparison between one region and another. Observation of the mean annual evaporation for various stations, mostly within the United States, have been made, and the result shown by lines drawn through places where the rate is the same. A map showing this data, on which the figures indicate the depth of evaporation in inches, is here presented. The systematic study of evaporation, and especially the part played in it by plants, has scarcely more than been begun on this continent, and important results concerning its influence on atmospheric conditions are to be expected. The subject is also of great importance in reference to agriculture, the prevention of frost, etc.

The great storehouse of information pertaining to the weather and climate of the United States is the numerous publications of the United States Weather Bureau, Washington, D. C. Similar bureaus exist at the capitals of Canada and Mexico, which have issued valuable reports.

Of the many elementary and popular books on meteorology, the following will be found helpful in continuing the study of the subjects outlined in this chapter:

• Davis, W. M. Whirlwinds, Cyclones, and Tornadoes, Lee & Shepard, Boston, 1884; Elementary Meteorology, Ginn & Co., Boston, 1894.
• Ferril, W. A Popular Treatise on the Winds. Wiley & Sons, New York, 1889.
• Greely, A. W. American Weather. Dodd, Mead & Co., New York, 1888.
• Maryland Weather Service, vol. i, Baltimore, 1899. Contains a valuable bibliography.
• Russell, T. Meteorology. Macmillan & Co., New York, 1895.
• Shaler, N. S. Aspects of the Earth. Scribner's Sons, New York, 1889.
• Waldo, F. Modern Meteorology, Scribner's Sons, New York, 1893; Elementary Meteorology, American Book Company, New York, 1896.

CHAPTER IV

From a geographical point of view, the broadest features in the flora of North America are the forested and unforested areas. The distribution of the forests, prairies, and treeless plains as they existed previous to the coming of Europeans is shown on the accompanying map. For the portion of the continent to the northward of Mexico the data on which this map is based are much more abundant than for the southern portion.

As is indicated on the map just referred to, the forests of North America in a general way form a broad belt, for the most part within the influence of winds from the ocean, which surrounds a large area of treeless plains and plateaus in the west-central portion of the interior continental basin, but is broken and rendered irregular in its southwestern part of the treeless valley of the Great Basin region. The irregular circular belt of tree-covered land is closed at the south by the forest on the lowlands of Mexico and Central America. This vast forest belt, extending from the Atlantic to the Pacific, and from Panama to northern Canada, presents great variations even in its larger features, and, for convenience, and also with the aim of expressing in a rough way natural relationships, needs to be subdivided for purpose of study. The basis for such a subdivision has already been suggested, as the forests, like all other divisions of the life of the continent, are an expression of climatic conditions—that is, the boundaries of the botanical and zoological provinces should agree with those of the climatic provinces.

On this basis we have the tropical forest, which covers the more humid portions of the east and west margins as well as all of the southern portion of Mexico, together with nearly all of Central America and the West Indies, and includes the southern extremity of Florida. Within the tropical forest, however, there are high mountains on which trees with the general characteristic of those more northern floras find a congenial habitat. The two austral and the transition provinces are to a great extent clothed with diversified forests, which are naturally divided into two portions: an eastern division, embracing the Atlantic and Gulf border of the United States, together with the eastern part of the Mississippi Valley and the Great Lakes region; and a western division, in which is included the lands bordering the Pacific from near Mount St. Elias southward to the vicinity of San Francisco, and also several irregular branches or detached island-like areas on the Pacific mountains, in the United States and Mexico. The former of these divisions may, in a general way, be termed the Atlantic, and the latter the Pacific forest. Separating them is the treeless west-central portion of the Continental basin. Both the Atlantic and Pacific forests merge at the north with the boreal forest, which extends diagonally across the continent from Newfoundland to Alaska. Peninsula-like and island-like areas occupied by the boreal forest occur in the sea-like expanse of the transition and austral provinces, on both the Atlantic and Pacific mountains.

The tropical and boreal forests have their greatest extension from east to west or with the parallels of latitude, and are remarkable for their uniformity in general characteristics, the reason being that climatic conditions, and especially the temperature in summer, change less rapidly along east and west than along north and south lines. The Atlantic and Pacific forests, on the other hand, have their greatest extension across the parallels of latitude, and hence experience marked changes from locality to locality in both temperature and precipitation, and are characterized by conspicuous changes from one locality to another in the genera and species of trees of which they are composed. In each of the areas occupied by the major divisions of the encircling continental forest belt there are marked variations in elevation, which are accompanied by corresponding climatic changes, and hence by modifications in the forest growths. Of all portions of the continental forest belt, variation in elevation is least marked in the forests of Canada, and for this reason, in part, we there find the most uniform and most monotonous of all the forests of the continent. The influence of elevation, however, on climate and on both plant and animal life is greater for a given measure, as for 1,000 feet, in the torrid than in the cool or cold zone, for the reason that the possible range in climatic conditions is much greater at the south than at the north.

The Tropical Forest.—There are great areas in southern Mexico which are clothed with a typical tropical forest; while other similar forests cover nearly all of the lower portions of Central America, the larger or more rugged West India islands, and the southern extremity of Florida. Throughout this vast region, within the influence of the trade-winds and of the equatorial rains, the forests are luxuriant and beautiful, except on lowlands not adjacent to the windward side of mountains. The characteristic trees of the hot, humid lowlands extend up the mountain to an elevation of some 4,000 or 5,000 feet, where a change to the aspects familiar in the lowlands of the temperate zone begins, and palms give place to oaks and pines.

Of the many features of the tropical forests which impress a traveller from colder regions, none excite greater wonder than the large number of vegetable species growing in close proximity. It has been said, and apparently the statement cannot be successfully challenged, that a greater variety of plants may be collected on 100 square yards of surface in the humid, tropical lowlands than can be found on 100 square miles in the forest of central Canada. It is probably safe to extend this striking contrast by saying that of the trees on a typical area in the tropical forest of the size mentioned, there are in many localities more species than in the whole of the subarctic forest.

Among the characteristics of tropical forests is the presence of many kinds of plants on a limited area, hundreds of species struggling upward to the light where there seems room but for one; the variety of mosses and lichens; the profusion of flowering parasites; the luxuriance of the vines, many of which are armed with spines; and the abundance of the remarkable aerial roots termed lianas. Of the last there is a great variety, some of them of large size and surprising length; they frequently descend from plants entwined among the topmost branches of great trees, looking not unlike the cordage of a forest of masts in some crowded port, and on reaching the ground send out rootlets in the humid soil.

In the depths of a tropical forest it is always twilight. Even at noontide no shafts of yellow sunlight reach the ground to glorify mossy banks and flower-gemmed dells, as in the open woods of temperate climes, but a diffused greenish light, producing weird effects, alone penetrates the dense leafy canopy far overhead. The roots of even the larger trees in these hot, humid forests do not have to descend deeply in order to find the necessary moisture or to receive protection from frost and sudden changes of temperature, but are usually widely expanded and thickly interwoven over the surface. The earth from which the dense vegetation derives nourishment is surprisingly deficient in vegetable mould, which is a characteristic feature in the moist forests of temperate and even subarctic regions, where the complete decay of dead vegetation is long delayed. In the tropical forests the annual supply of dead vegetable matter suitable to be transformed into humus is far greater than on a corresponding area in the woods of more northern regions, but decay is so rapid, owing to the uniformly high temperature and the conditions favouring the multiplication of bacteria, that even great trees on falling quickly disappear; in many instances, the forms of prostrate tree trunks are preserved and overgrown with luxuriant mosses or gorgeously festooned with ferns and orchids, but soon become fragile shells from which nearly all the woody tissues have been removed by decay or by swarming colonies of insects. Where life is so exuberant and the wants of growing plants so great it seems as if the food supply was insufficient, and that none could be spared to accumulate on the ground and form a soil.

The two most characteristic and distinctive classes of plants in the tropical forests are the palms and the ferns, each of which is represented by many genera, a large number of species, and multitudes of individuals, and in each class there is a gradation in size from low herbaceous growths to arboreal forms.

In every way worthy of first mention among the plants of the Caribbean forests are the palms. A characteristic portion of the forest referred to occurs in Cuba, where, as is stated by R. T. Hill in his recently published and attractive book descriptive of the West Indies, there are some 26 species of palms, which give variety and beauty to the scenery of the "Pearl of the Antilles," as well as shade and food to its inhabitants. At the head of these for height and grace of form stands the royal palm, which might well be chosen for the emblem of the fair island it adorns. The wide-spreading crown of glossy pinnate leaves of this species is borne on a spindle-shaped stem of tough fibrous wood—so strong and pliant that it defies even the hurricane—in many instances 150 feet above the ground. The tree is a marvel of beauty and elasticity, and, fortunately for Cuba, is one of the most abundant of the larger trees on the island. It is met with almost everywhere; in the centre of broad pasture-lands it often stands alone, tall and straight, while bordering the cultivated fields of the rich planter it forms a shady avenue to his dwelling. This well-named royal palm has also been called the blessed tree, for every part of it has its usefulness to mankind. Certain medicinal qualities are claimed for its roots; the outer portion of its trunk is easily split into boards for use in making houses and furniture for the poorer people; in the centre of the cluster of young leaves at the summit is a tender substance which is eaten raw, or cooked as a vegetable, or preserved with sugar as a table delicacy. The broadened leaf-stalks where they leave the main stem form a sheath-like expansion resembling a thin board, often four to six feet long, which is made to serve a variety of purposes, such as plates, and when soaked in water becomes pliable and may be fashioned into baskets and dishes for cooking, and at the same time furnishes salt for the seasoning of the boiling vegetables or meat.

The world-encircling cocoanut-palm is found about the shore of tropical North America, and there, as elsewhere, serves a great variety of uses, being a greater blessing, especially to the natives and the poorer descendants of European and African immigrants, than even the royal palm. The economic importance of its wood-fibres, leaves, and fruit are too well known to require re-enumeration.

While the wealth of palms is confined to the hot, moist regions of Mexico, Central America, and the West Indies, several members of the same great family are found in the United States. The royal palm is native to southern Florida, while the low fan-palms cover much of the northern portion of the same State, and occur even about the Ozark Hills in Arkansas, and the palmetto, growing to be a stately tree, is found near the coast in the Carolinas and is the emblem of South Carolina, the "Palmetto State."

The ferns, although abundant, especially in moist woods from Alaska southward, throughout the continent, reach their greatest variety and richest luxuriance in the West Indies and Central America, where the graceful and most artistically beautiful tree-ferns add an indescribable charm to the always varied foliage. The tree-ferns grow farther up the mountains of the torrid zone than do the larger palms (in the same manner that the smaller ferns extend much farther north than the most hardy palmettoes), and form a conspicuous feature in the foreground of nearly every wide-reaching prospect in the more elevated portions of the West Indies, Central America, and south-central Mexico.

In addition to the palms and ferns, the tropical forests of North America contain a large number of trees of great economic importance. Chief among these are the mahogany, which is native to the lands bordering the Caribbean Sea and Gulf of Mexico, and reaches the largest size and produces the most beautiful and most highly prized wood on Cuba, Haiti, the Bahamas, and Jamaica. As is well known, this hard, dark, heavy, fine-grained, and exceedingly durable wood has been used for the best grades of cabinet-work for about two centuries, and is still unsurpassed for the beauty of its grain, susceptibility of a high polish, and the several ways in which it is adapted for the carver's tool. On account of the great and long-continued demand for its wood it has become scarce in all but the most inaccessible localities. When allowed to reach full maturity it is a large, wide-spreading tree with numerous branches, looking not unlike a giant oak, but has pinnate leaves and small, although somewhat conspicuous, white flowers.

Another gift of the tropical forest is the lignum-vitæ, which furnishes the exceedingly tough, hard, resinous wood preferred above all others for the making of pulleys, mallets, etc. Many other highly prized woods, not known, however, by familiar names, are also found in the varied forests of tropical America, as well as numerous vegetable dyes, such as logwood, brazil-wood, indigo, etc.

The lands of the Caribbean-Gulf region are credited with having introduced to civilized man the potato, Indian corn (maize), and tobacco, although the home of the former is probably in the Andean portion of South America. Indian corn grows luxuriantly not only in the hot lowlands of Mexico, but on the border of the central table-land of that republic, where it is supposed to be indigenous, and has now become one of the leading crops of temperate North America, and is cultivated in many other portions of the world. Tobacco was found under cultivation in Mexico at the time of the first coming of Europeans, and retains for its familiar name the appellation of the district where it was first seen. From Mexico also come the dahlia and the giant sunflower, as well as the various species of aloes and cacti now so common in gardens and conservatories the world over.

Of all the plants, excepting Indian corn and the potato, which are native to the region under review, none has proved such an unalloyed blessing to civilized man as the cacao-tree. As this tree is unfamiliar to most residents of temperate lands, it may not be unprofitable to transcribe in part a description of it from Rhind's Vegetable Kingdom. The tree is very handsome, from 12 to 16 feet high, with an upright trunk some 5 feet high; the leaves are lanceolate, with entire margins, and of a bright-green colour; the flowers are inconspicuous, reddish, with yellowish sepals; the fruit, attached by short stems to both trunk and branches, has a yellowish and reddish colour, oblong, about 3 inches in length, and consists of a fleshy rind, half an inch thick, containing a white pulp in which are imbedded about 25 seeds. The seeds, when roasted, freed from their husks, and ground, furnish the chocolate so extensively used, especially in France and Spain and in the former Spanish colonies, and is increasing in favour among English-speaking people.

Vanilla, which is used in flavouring chocolate as well as many other dishes, was also found in use among the Aztecs at the time of the Spanish conquest. The vanilla-plant is a climbing vine, with lanceolate leaves 18 inches or more in length, and produces a pod containing bean-like seeds. The pods and seeds when properly dried furnish the flavouring extract of commerce.

Although the trees which yield rubber in America, as well as the cinchona, from the bark of which quinine is obtained, are justly to be accredited to South America, yet certain varieties of these useful plants occur in Central America and are under cultivation as far northward as central Mexico.

A more detailed account of the plants of great utility in one direction or another native to the tropical forests, should include plantains, bananas, and yams, the wide distribution of which, largely by human agency, throughout the torrid zone is well known. The delicious pineapple is native to the Caribbean region, and was found in the markets of the Aztecs by the early Spanish invaders, although perhaps indigenous to other lands as well. In Mexico especially, but on the borders of the tropical forest and in the drier interior, grows the agave, from which the national beverage, pulque, is obtained, and another species of the same peculiarly American family of plants supplies great quantities of the tough fibre known as sisal or henequen hemp, particularly on the stony, arid portions of the peninsula of Yucatan. Of interest to children especially is the fact that Mexico exports some 3,000,000 pounds of chewing-gum each year, which is obtained from a plant there growing wild. To this list of indigenous products may be added ginger, arrowroot, etc., as well as many fruits scarcely known outside the tropics, such as the mango, alligator-pear, breadfruit, and numerous others. This hasty enumeration might be greatly extended or presented in more detail, but probably enough has been said to indicate the great and probably as yet but partially determined economic importance of the vegetable products of the torrid portion of North America.

Associated with the tropical forest, but thriving best in an advanced skirmish-line about its drier inland borders, is a group of plants indigenous to the two Americas—the strangely shaped and spinous cacti. One of these, the prickly-pear, as it is termed on account of its pear-like edible fruit, is the emblem of Mexico. A fit legend to place about this unique heraldic design would be the motto inscribed on the rattlesnake flag of colonial days in America, "Don't tread on me," as every one will appreciate who has travelled in the southwestern portion of the United States or in the upland regions of Mexico.

The cacti extend from South America northward through the lands bordering the Caribbean Sea and Gulf of Mexico, and east of the Mississippi are represented by a single genus, Opuntia—the prickly-pear, or Indian fig, as it is often termed—which grows in dry situations as far north as Massachusetts and Michigan. In the Great Basin several genera of cacti are plentiful, especially on dry, stony uplands, and two species reach as far northward as the Canadian boundary. Although the cacti tribe is widely distributed, the region where it presents the greatest variety and the largest individuals is in the dry, semi-desert portions of Arizona and the table-lands of central Mexico. It is most at home on sterile, rocky ridges and amid bare cliffs where there appears to be but little soil, but the strong roots strike deep into the earth in search of moisture. The cacti present great diversity of form and an indefinite differentiation of stem and leaf. In fact, there are no easily recognised leaves in the ordinary sense of the term, but the fluted and jointed stems perform the function of foliage. The plants are economical of moisture, and not only present a minimum of surface for evaporation or transpiration, but their epidermal tissues are for the most part without pores, thus retarding the escape of the moisture drawn from the seemingly dry soil.

In size and shape the cacti present great variety, ranging through all gradations from the thick, strongly jointed, pad-like expansions of the prickly-pear, a few inches high, growing in widely extended clusters and massive globular forms, looking not unlike spiny melons, 2 or 3 feet or more in diameter, to jointed and fluted columns, bristling with sharp spines, the largest of which, known as the candelabrum cactus, attains a height of from 40 to 60 feet. In this the largest of all the cacti, which is not uncommon in Arizona and adjacent portions of Mexico, the central upright stem, frequently 20 inches or more in diameter, sends out from 1 to perhaps 7 or 8 club-shaped branches, which leave the parent stem nearly at right angles, but soon bend upward and become parallel with the central stalk, which they frequently surpass in height, their form thus suggesting a branching candlestick or candelabrum.

In spite of the bizarre and frequently repellent appearance of the cacti as seen under cultivation, in their barren homes they are in harmony with their surroundings, and add a characteristic, and even beautiful element to the scenery of the parched and generally desolate valleys and rocky slopes where they thrive best. Their blossoms are large, usually either white or brilliantly coloured, and expand in the hot, dry air, fully exposed to the intense sunlight, and present a freshness and vigour which tell of the abundant store of moisture within the thick rind inclosing their stems. The showy flowers are borne close to the body of the plant or at the ends or edges of the inflated pad-like leaves, and are scentless, except in the case of a few night-blooming species, and attract insects from afar by reason of the conspicuousness of their widely expanded corollas. The fruits also are usually conspicuous, and present many rich tints of red and yellow, which at a little distance give them the appearance of flowers. The fruit of several species are edible, and even delicious, especially when gathered fresh from the thorny stems and eaten on the desert, perhaps many miles from the nearest spring or stream. One species of cactus growing abundantly in Mexico and known as the cochineal-fig, is inhabited by the cochineal-insect, from which the highly prized dye of that name is obtained.

A companion of the cacti in the arid region where they flourish best is the yucca, or Spanish bayonet, which sometimes attains the size of small trees and throws out several branches. Its leaves are stiff, thick-stemmed, and each one terminated by a sharp spine, as is well known from the many examples to be seen under cultivation in Europe and America. The flowers are white and borne in luxuriant showy spikes a foot or two in length, and sometimes give to dry, rocky slopes the appearance of a luxuriant garden.

The cacti, yuccas, and associated plants of the most arid portions of the continent stand far apart, without mutual support or shelter, and find protection in their spines, thick rinds, and frequently acrid juices. Their colours are usually neutral, grayish green, rendered still more inconspicuous by the dust that settles on them, but their flowers are as a rule conspicuous, thus serving to attract pollen-bearing insects, and their fruits are in many instances brightly coloured, and furnish food for birds and other animals, which assist in the distribution of their seeds.

The Atlantic Forest.—The originally forest-covered eastern portion of North America, referred to under the term Atlantic forest, embraces the region from the eastern coast of the continent inland across the Appalachian Mountains and interior Continental basin to the eastern border of the prairies or plains; its southern limit, in a general way, is the coast-line of the Gulf of Mexico, but the arbitrary boundary, dividing it from the tropical forest, crosses the southern portion of Florida, and at the extreme southwest is drawn at the Rio Grande. The northern boundary of the Atlantic forest is also an arbitrary line, and follows the fiftieth parallel of latitude from the mouth of the St. Lawrence westward to the region about the Lake of the Woods; along this boundary the varied Atlantic forest merges with the monotonous and mostly coniferous subarctic forest. The region thus roughly outlined comprises over 2,000,000 square miles, and was at the time of the first coming of white men to America almost completely forest-covered, but the natural conditions are now profoundly modified, and to a great extent the trees have been cut or burned, and the land they shaded converted into cultivated fields.

The Atlantic forest as a whole has two leading characteristics, the first being the great variety and frequently large size of the deciduous trees—that is, of broad-leaved trees, such as the oak, hickory, elm, maple, chestnut, etc., which drop their ripe leaves each fall and renew them the following spring—and the second, the intermingling of the trees of the class just mentioned with the coniferous trees, such as the pine, spruce, tamarack, etc., which have narrow, needle-shaped leaves and are usually designated as evergreens. While these general statements are sufficiently accurate for our present purpose, it is to be remembered that some of the broad-leaved trees (Angiosperms) are evergreen, especially in the southern portion of the Atlantic forest, as, for example, some of the oaks, the magnolias, the holly, etc.; while at the north, certain of the conifers (Gymnosperms) shed their leaves each fall, as is conspicuously illustrated by the yellow of the tamarack or larch forests of the northeastern portion of the United States and eastern Canada, in November, and the bright green of the same trees in May of each year. It is in the intermediate temperate region, between the mostly evergreen coniferous subarctic forests and the mostly evergreen broad-leaved trees of the Caribbean forest, that the wonderful transformation in the colours of the mountains and plains each autumn becomes the most conspicuous feature in the annual round of seasonal changes as expressed by the vegetation.

Of the two classes of forest-trees, represented by the oak and the pine, which are intermingled and struggle with each other for supremacy in the Atlantic forest, it is difficult to say which is the more beautiful or which is of the greater service to man. The broad-leaved trees give us our hardwoods, used extensively for furniture, the interior finish of buildings, and for the manufacture of tools, farming implements, wagons, carriages, sleighs, etc. To a great extent it was the availability of these strong, tough, hard, and durable woods which has made American tools and implements of such a high grade of excellence that they are in demand in every civilized country. For example, the American ax-helve, made of hickory, is almost a work of art, as well as of utility, and it is prized above all others by foresters the world over. The same tree has aided no less efficiently in the popularity and excellence of American carriages and sleighs, the equal of which for lightness, strength, and durability has not been reached in other countries. The pines and their near relatives furnish what unfortunately has been considered an unlimited supply of easily workable lumber, suitable for building houses, vessels, bridges, and many other purposes. Of the pine lumber supplied by the Atlantic forest, there are two principal varieties, the far-famed white pine, furnished by New England, the Great Lake region, and southeastern Canada, and the yellow pine, which comes from the South Atlantic and Gulf States.

Of the Angiosperms which reach the dignity of trees, the Atlantic forest possesses a variety and abundance not exceeded elsewhere in the world. The most characteristic examples are the maples, elms, oaks, hickories, walnuts, chestnuts, ashes, basswoods, birches, tulip-trees, magnolias, liquidambar, tupelos, sycamores, etc., nearly all of which are represented by a number of species or varieties and vast numbers of individuals. While this diversity is found throughout the forests of the east-central part of the continent, certain regions are characterized by the abundance and large size of the trees belonging to one or to a few genera, so that a striking change is met with as one travels in any direction. The maples and elms reach their greatest size and abundance at the north, especially in New England, and thence westward to the Mississippi Valley, where they are the favourite shade-trees of villages and farms. In regions where the forests have been removed choice specimens of these trees have frequently been saved or subsequently planted, and standing alone, without competition and fully exposed to the light, reach great perfection of form and a high degree of beauty. The oaks are represented by a large number of species and varieties throughout the entire Atlantic forest, but reach their largest size and greatest abundance, both of species and individuals, in central and southern portions of the eastern United States. The same may be said also of the hickories, except that the maximum in reference to size, number of species, and abundance is attained in the region of the Ozark Hills. The tulip-tree, so named from the profusion of showy yellow blossoms it bears, is large and wide-spreading, with broad, dark-green leaves, and has the centre of its habitat in Kentucky, where many magnificent examples occur along the fences separating the broad meadows and rich pastures of the region of the blue grass, but thrives also from the Atlantic coast westward to beyond the Mississippi, and from Ontario on the north nearly to the Gulf of Mexico on the south. Not only is the tulip-tree an ornament and a blessing on account of its flower-laden branches and dense shade, but its white, even-grained wood is of great value.

To give even a list of the deciduous trees which flourish and reach a high degree of perfection in the Atlantic forest would require far more space than is at present available. There is one other genus, however, which cannot be passed by even by a casual observer, and that is the magnolia, one species of which, the grandiflora, is the most magnificent of all the splendid broad-leaved trees of America. This, the largest and finest of the several species of its genus found in the eastern portion of the United States, attains a great size in the southern Appalachian region, but is best developed in the lower portion of the Mississippi Valley. It is frequently from 50 to 80 feet or more in height, wide-spreading, and in many instances upward of 3 feet in diameter, with dark-green leaves which do not fall in the autumn. In spring the dark foliage is beautified by cup-shaped blossoms of creamy whiteness and remarkable fragrance, which measure 3 or 4 inches in diameter. When the magnolia is in blossom it becomes a centre of delicious perfume and a colony of insect life. Its wood, although creamy white and excellent for cabinet-work and interior finish of houses, has not as yet found favour for these or other purposes.

With the exception of a few species of broad-leaved forest-trees found in greatest perfection in the northern portion of the Atlantic forest, they reach their greatest development in size, number of species, and density of growth in the southern portion of the broad Mississippi basin, where, in addition to magnolias, the tulip-tree, etc., chestnuts, hickories, oaks, and many other genera grow side by side and attain great height and dignity. This is also the centre of dispersion of the American hawthorns, which reach a size and beauty unrivalled elsewhere. The Osage orange is peculiar to this region, and the red cedar (juniper), the most widely distributed of all the American conifers, and also the yellow or southern pine are there at their best. Much of this region still retains its primitive wildness.

The great extent of the Atlantic forest in latitude, the topographic diversity of the region it occupies, and its exposure on the east to maritime and on the west to continental climatic conditions, have led to great variations within itself. From the coast of New England westward and including the entire drainage basin of the St. Lawrence, together with an extension southward along the Appalachians, the forests are composed largely and over extensive areas almost wholly of coniferous trees. This region of northern evergreens contains in its southern portion sturdy growths of broad-leaved deciduous trees. The spruces, the most characteristic of the trees of the subarctic region, are present in abundance on the mountains of New England, and still form a dark mantle over the Adirondack hills; but on the less elevated lands adjacent the white pine dominated and outnumbered all its rivals in the primeval forest.

The white or Weymouth pine, which up to the present time has proved to be of greater commercial value than any other tree on the continent, extends westward from southern Newfoundland and the coasts of the maritime provinces of Canada to Minnesota, and occupies nearly the entire drainage area of the St. Lawrence, together with an extension southward along the Appalachians nearly to their southern limit.

The white pine is a large tree for the region in which it grows. Its height is from 70 to 150 feet, with a diameter at the base of from 3 to 9 feet. It thrives best on sandy soil and hills of glacial drift, and endures a severe winter climate, as well as the frequently long-continued droughts of the hot summers. Its wood is soft, compact, with an even, straight grain, and is not conspicuously resinous. The sap-wood is nearly white and the heart of a light brown, slightly tinged with red; it is easily worked and susceptible of a good polish; it is more extensively used for boards, shingles, etc., than any other wood in the eastern portion of the continent, and is in demand also for cabinet-work, the interior finish of buildings, ship-building, and many other purposes.

The southern pine—known also as the "long-leaved pine"; "Georgia pine," for the reason that the lumber derived from it was first extensively shipped from that State; "yellow pine," in reference to the golden colour of its wood; and "hard pine," in distinction from the softer white pine—is another valuable species. The tree with these several synonyms, of which the term southern pine will here be used, forms open forests with but scanty undergrowth, over a region extending from near the Atlantic coast in the Carolinas and Florida, westward to the delta region of the Mississippi, and reappears again to the southward of the Ozark Hills. Although not so large, and to many admirers of beautiful trees not so picturesque or pleasing as its relative in the more rigorous climate of the St. Lawrence basin, the southern pine, growing within the reach of the moist, warm winds from the Atlantic and Gulf of Mexico, is still an attractive tree, especially when young and when freedom is afforded to expand its boughs. It is seldom over 100 feet high, and as cut for lumber has on an average a diameter of about 2 feet at the base, although individuals measuring 3 or 4 feet in diameter are not rare in certain favoured areas. It grows best on dry, sandy soil, outside the flood-plains of streams, where it forms monotonous forests, with but few intergrowths of other trees. The wood is heavy, hard, strong, durable, coarse-grained, very resinous, and of many shades of brown and yellow. When sawed into lumber, it serves a wide range of uses, more especially for the frames of buildings and ships, and for the floors and interior finish of houses.

Next to the southern pine, the most characteristic tree of the Atlantic coastal plain southward from Virginia and westward through the Gulf States, is the cypress, also a conifer, but, like the tamarack, sheds its leaves in the autumn. The cypress grows especially in swampy localities, and has a widely expanded base, suitable for support on marshy soil, and reaches a large girth, although seldom over 75 feet high. Aged and most picturesque examples are growing in isolated positions in Lake Drummond, the central water body of the Dismal Swamp, and in many other similar situations in the belt of low country fringing the borders of the Atlantic and Gulf of Mexico. Its wood is used for most of the purposes for which the southern pine is employed, and now that the white pine is approaching extinction, is to a considerable extent supplying the demand for cabinet-wood.

In glancing at the larger and most numerous trees of the Atlantic forest, and those of greatest utility, we should not neglect the humbler plants, usually of little, if any, purely commercial value, but priceless on account of their beauty and the fragrance of their flowers, which grow beneath the shade of their larger and more stately associates or are content to possess the local areas, perhaps high on the mountains, where the conditions of climate or soil are unfavourable for the growth of large trees. Throughout the eastern portion of the United States, but more especially on the slopes and summit portions of the Appalachians, there are many species of azalea, laurel, rhododendron, etc., which grow luxuriantly and in spring and early summer furnish a wealth of bloom that is scarcely rivalled elsewhere on the continent. In this same region also, but extending westward to Michigan and Minnesota, and even to eastern Nebraska, grows the redbud or Judas-tree, which each May becomes as thickly set throughout all its branches with small crimson blossoms as are the tree-like coral in tropical seas with expanded polyps. This beautiful tree of low growth many times gives to the mountains of Virginia, when seen from a distance, a delicate blush like that which the osiers earlier in the spring impart to the marshy vales and river-banks. A companion of the redbud, but far more widely distributed, is the dogwood or cornel, of several species, the most conspicuous of which, and in the Appalachian region the most common, is the flowering dogwood. In May and June this species puts out a profusion of clusters of small greenish flowers, each of which is surrounded by a broadly expanded and very showy corolla-like involucre, composed of four white or pinkish inversely heart-shaped leaves. When the cornel is at the height of its spring-time glory it stands forth amid the tender greens, russets, and pinks of the unfolding leaves of the various trees and shrubs among which it grows as if the orchards and forests had been commingled by some fairy gardener. In autumn the cornel again becomes conspicuous in the woodlands by reason of its clusters of coral-red fruit.

In the splendid Atlantic forests, with their marvellous intermingling of shining pine-needles, broad, swaying leaves, and many-coloured trunks, there are also vines and creepers sometimes forming impenetrable tangles, as where the broad leaves of the wild grape grow in pendent sheets of green from supporting trees, or the jessamine fills the air with fragrance. Of the many vines which entwine the trunks of trees, mantle the rocks, and quickly claim abandoned fields, especially in Virginia and neighbouring States to the southward, none is more beautiful or more highly prized for the charm it adds alike to fields, fences, and forests than the familiar Virginia creeper. The glory of this widely distributed vine comes in the autumn when its leaves change from green to the most brilliant scarlet. During the season of harvest also, when the trees are arrayed in their greatest splendour, the ground is yellow with golden-rods or purple with asters. This annual carnival of colour embraces the entire Atlantic forest, but is most resplendent in the region of the Hudson and St. Lawrence. A charming little denizen of the Atlantic forest is the lowly and humble arbutus, or Mayflower, which springs up through the dead leaves carpeting the ground in early spring, and fills the air with its delicious perfume. The Mayflower is a trailing plant, but a few inches high, with rounded or oval leaves, which remain green all winter and furnish a pleasing setting for the small pink or rose-coloured blossoms, which appear in early spring even before the snow has melted. It reaches great perfection beneath the pines of New England and about the Laurentian lakes, but extends far southward along the Appalachians, where elevation gives conditions similar to those of the lower region at the north.

The Atlantic forest reaches its western limit in the Mississippi basin (Fig. 28), and is succeeded westward by treeless prairies, which merge along their western margins with the drier and less completely grass-covered high plains adjacent to the east base of the Rocky Mountains. The forest does not terminate abruptly, as on the border of a cleared field, but by gradual transitions. As its western limit is approached, a change in the species is noted, trees which thrive on uplands and can sustain long-continued summer drought replacing the species best adapted for more humid conditions. The forest is most extended, however, along the streams where white-trunked cottonwoods, frequently of great size, with widely spreading branches, extend even into the region of the great plateaus. Much of the prairie region in Illinois, Iowa, etc., was originally nearly surrounded by forest growths. The natural condition of the prairies and higher plains adjacent to them on the west and the reason for the limits set to the western extension of the Atlantic forest will be considered later under the heading Prairies and Plateaus.

The Boreal Forest.—From Nova Scotia, Newfoundland, and Labrador a forest composed mainly of a few species of coniferous trees extends westward, and after passing the southern extremity of Hudson Bay, is prolonged northwestward across the continent and in the region of the mouth of the Mackenzie nearly to the shore of the Arctic Ocean. It extends also through central Alaska to within about 100 miles of the border of Bering Sea. This vast transverse forest belt which unites the northern extremity of the Atlantic forest with the northern portion of the Pacific forest is over 3,000 miles long from southeast to northwest, and on an average fully 600 miles wide. On the north, more especially in arctic Canada and as it approaches the shore of Bering Sea, it thins out, owing to the severity of the winter climate, the trees become dwarfed and stunted in much the same way as the trees adjacent to the timber-line on high mountains, and is succeeded by the broad treeless plains of the Barren Grounds and tundra. Along its south-central border its extension is again limited by climatic conditions, principally the dryness of the hot summers. The trees are there scattered or form isolated groves to the south of the general forest boundary, and are finally succeeded by the treeless prairies and interior plains and plateaus. On the east the great northern forest merges with the pine of the northern portion of the Atlantic forest, and in a similar way at the northwest passes by insensible gradations into the north extension of the coniferous forest growing on the Pacific mountains. In each of the instances there is no well-defined boundary between the east and west belt of northern forests and the north and south forest belts adjacent to the Atlantic and Pacific.

The boreal forest presents a striking contrast to the forests of the torrid zone and to the greater portion of the forests of temperate regions in the fact that it is composed of but a few species of trees. Monotony which becomes oppressive to one who lingers long in its sombre shade is its most conspicuous characteristic. In the main it is composed of but eight species of trees, namely, white and black spruce, larch or tamarack, canoe-birch, balsam-poplar, aspen, balsam-fir, and the gray pine. Of these the spruces are the most abundant and most characteristic as well as the most northern trees of the continent. They frequently reach sufficient size to make them available for building log houses and for lumber.

Four of the species mentioned above, namely, the white spruce, canoe-birch, balsam-poplar, and aspen, cross the entire breadth of the continent from Labrador to Alaska, but the pines and firs in the east and the west are of different species. The larch or tamarack, which forms such an important feature of the forest in eastern Canada and about the Laurentian lakes, extends westward to beyond Hudson Bay, but is represented by other species in the Mackenzie and Yukon basins, and in the northern portion of the Pacific mountains. The region occupied by the great northern forest is interspersed with lakes, some of them of large size, and by innumerable swamps. The spruces and the gray pine grow on the uplands between the lakes and swamps, while the cold, wet bottom-lands are occupied by poplars, dwarf birches, willows, and alders. In the north, near where the forest breaks into outstanding groves and finally gives place to grassy hills, as along the Porcupine River in Alaska, the foliage in the lowlands becomes golden in autumn and forms irregular, far-reaching avenues of brilliant colour separating the hills, which are black with spruce-trees or shimmer with the soft gray tints of ripened grasses. There is much that is beautiful and even lovely along the poleward border of the great forest, but within its deeper recesses the ground is covered with mosses and lichens, and the stiff, sombre trees have a monotonous similarity and unbending rigidity.

In spite of the great area covered by the boreal forest, it being one of the greatest, if not the most widely extended continuous growth of arboreal vegetation in the world, it is of comparatively small economic importance. Even if the trees were within the reach of a market, their wood is of inferior quality and not generally suitable for lumber. A modern industry has been developed, however, which may bring it into demand, namely, the manufacture of wood-pulp, so largely employed in the making of paper and for other purposes.

The Pacific Forest.—In the northern portion of the Rocky Mountain region in Canada and Alaska the boreal forest, as already stated, merges by insensible gradations with the forests occupying the Pacific mountains from Alaska southward to Mexico. The junction line between the two is irregular, and what are essentially outliers of the more northern forest occupy the higher portions of the mountains in the western portion of the United States.

The Pacific forest begins at the north near Mount St. Elias, and at first occurs on isolated areas separated by ice-fields and inland reaches of the ocean, but in southeastern Alaska and on the numerous islands adjacent becomes more continuous and extends eastward far into British Columbia. As the timber-line in that region has an elevation of but 2,500 feet at the extreme western extension of the forest, although gradually rising southward, large portions of the mountains are treeless and barren. In the United States, on account of increasing dryness of the valleys from north to south, the forest becomes broken into many detached portions, which occupy the mountains and higher plateaus and in general are restricted to higher and higher locations with decrease in latitude. This distribution illustrates in a striking manner the dependence of trees on humidity. The forest is densest and the trees in general of greatest size and occur at the lowest elevations on the northwest portion of the Pacific coastal region, where the rainfall is excessive and distributed practically throughout the entire year. The Coast Ranges from Alaska southward to central California, as well as the Cascade Mountains and Sierra Nevada, are tree-clothed. In the interior, and especially in the central and southern portion of the Pacific cordillera, where the valleys are hot and dry in summer, trees are absent, and even the borders of the rivers in many instances without shade. In Canada the trees frequently extend across the lowlands, but in Montana and Idaho the valleys resemble the treeless plains to the east of the Rocky Mountains, while the uplands and the lower mountain slopes are dark with firs and pines. Above the forest rise the barren and frequently perpetually snow-covered summit-peaks and ridges. In the Great Basin region, and from there southward, many of the mountains are practically destitute of trees from base to summit.

So vast is the region occupied by the Pacific forest and so varied the conditions dependent upon climate, soil, and elevation which influence its growth, that great variations in the genera and species of trees composing it are to be expected. This prediction is soon verified when one travels through the forest. The extremes may be indicated briefly by referring to the fact that at the north the trees are mainly spruces, firs, and cedars, and at the south include the giant cactus, arboreal yucca, and the fan-leafed palm. In its medial division are the great forests of western Washington and Oregon, composed mainly of firs and cedars, and the no less magnificent forests of redwood-trees on the Coast Ranges of northern California and the west slope of the Sierra Nevada. Like the boreal forest, the one under consideration is largely composed of coniferous trees, although in the valley, and especially along the borders of streams in southern Canada, Washington, etc., a few species of broad-leaved trees, such as the maple, cottonwood, ash, and alder, thrive in close association with dark conifers; while in similar situations farther south oaks growing in scattered groves give a park-like character to the land, as in the southern portion of California.

In contrast with the Atlantic region, the western portion of the continental forest belt is singularly lacking in broad-leaved trees, and such as are found are usually of small size and but little economic importance. This lack, however, is perhaps more than counterbalanced by the number both of individuals and of species and the great size and magnificence of the conifers.

One of the densest and in many ways most thoroughly representative portions of the Pacific forest where it occupies an excessively humid region occurs on the west side of the Cascade Mountains in Washington, inclusive of the Puget Sound basin and the region to the westward from which rise the Olympic Mountains.

In western Washington the forest is composed mainly, and, in fact, over large areas, almost entirely of two species of trees, namely, the red fir and the red cedar, each of which attains gigantic dimensions. Of these two species, the first is the more common, the larger, and by far the more important from a commercial point of view. It frequently, and, in fact, commonly, attains a height of from 200 to 300 feet, with a diameter at the base of from 8 to 10 or more feet. Not only do these magnificent trees reach such great dimensions, but they are thickly set over hundreds of square miles of territory. In thousands of instances the great trunks sheathed in rough thick bark rise straight and massive, with but a slight decrease in diameter, to a height of upward of 80 feet before the first branch is given off. The cedars, the intimate companions of the great firs, are of equally gigantic girth at the base, but taper rapidly to spire-like summits, usually from 100 to 150 feet above the ground, and are thickly set with small branches throughout. They flourish best in excessively moist situations and reach far up the mountains, particularly along the numerous watercourses; while the firs, although perhaps most at home on the less thoroughly water-soaked uplands, thrive on the banks of streams, the sides and summits of hills, and on steep mountainsides alike.

Mere enumeration of the number and size of the trees, however, fails to give an adequate impression of the astonishing magnificence of the wonderful forest of the Puget Sound region. Its grandeur is beyond description, and can only be fully appreciated by one who abides for weeks or months in its perpetual twilight. The great trees, shaggy with mosses and lichens of innumerable tints of brown, green, and yellow, do not form detached groves, as is so frequently the case in less humid lands, but are thickly set for mile after mile and league after league, as one threads his difficult way beneath them. So vast is the forest that a person travelling through it soon becomes impressed with the idea that it is interminable. Beneath the deep shade of the lofty boughs there is a rank undergrowth of young firs, cedars, and hemlocks, while in the valleys especially, and on the frequently inundated flood-plains of the streams, there is usually a tangled growth of vine-like maples, alders, elders, yews, etc. In this lower forest the most conspicuous and frequently too abundant plant is the broad-leaved and excessively spiny devil's-club, the foliage of which changes to brilliant yellow in the early autumn, and forms a most artistic setting for the spikes of crimson fruit borne at the extremities of the upward-bending ends of the usually prostrate stems.