Chapter 4 PLANT LIFE

If we take the trees as representatives of the flora of North America, and this seems to be the only practicable method in a general treatise, we find them growing most densely and presenting at the same time the greatest variety where the temperature is uniformly high throughout the year and the rainfall heavy and long-continued.

From the torrid lowlands the forests in general decrease in the variety and number of trees on a given area, both towards the north, where temperature becomes the controlling factor, and towards regions of small rainfall, where the leading adverse condition is deficiency of moisture. In the most highly favoured localities the struggle for existence between species and species and individual with individual is intense, exposure to the life-giving sunlight being the dominant aim of every one of the contending hosts. As drier or colder regions are approached, but few species can survive and the forests are characterized by their monotony. Where the conditions of heat and moisture are such that the existence of a species is precarious, the balance of power, so to speak, passes to the secondary conditions; and the texture and composition of the soil, slight differences in the relief of the land, and consequently in drainage or in the degree of exposure to light, prevalence of fires, etc., make themselves prominent and limit distribution.

Fig. 28.-Map showing the distribution of forests in North America.

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.

THE FORESTS

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-vit?, 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.

Fig. 29.-Douglas Firs, Vancouver, B. C.

Of still more lowly habits are the ferns, mosses, and lichens which form a thick, luxuriant, and ever-varied carpet over the black humus soil beneath. The ground throughout the forest is encumbered with fallen trunks, sometimes piled one on another to the depth of 20 or 30 feet, which, owing to the continuous moisture, remain undecayed for centuries. Not infrequently a massive cedar or fir, in size and shape not unlike a prostrate column of some great temple, supports three or more trees, each large enough to be cut for lumber, whose gnarled and twisted roots clasp the sides of their host and descend to the earth beneath. The beauty of these fallen giants when overgrown with thick layers of variegated moss and exquisitely decorated with hundreds of small hemlocks and a multitude of gracefully bending fern-fronds, always fresh in colour and usually beaded with moisture, is beyond the power of the most skilful artist to adequately portray. The fascination of the great forest is such that the explorer, although perhaps weary with forcing a passage through the dense undergrowths and climbing over prostrate trunks, is lured by its charms into more and more inaccessible retreats probably never before invaded by man, but at last finding that the wonderland has no attainable limits, is content to rest on some inviting couch of golden-tinted lichens and study the varied charms and endless details of the dream-like picture surrounding him.

From a commercial point of view the forest of the Puget Sound region is of immense importance. Lumber industries have been established there, with the most improved appliances for cutting trees, transporting the logs to mills, and sawing them into lumber, much of which is loaded on ships and widely distributed. So vast is the forest, however, that as yet the natural conditions are but slightly changed, except in the immediate vicinity of tide-water, but the destruction from axe and fire has only been begun; the waste that, no doubt, is to continue is most disheartening.

Another centre in the vast and locally differentiated Pacific forest, as typical in its way as are the dense growths of fir and cedar just referred to, occurs on the Coast Range of north California, where the redwood (Sequoia sempervirens) is the all-important and characteristic tree. This redwood forest begins at the south in the vicinity of San Francisco, and extends northward, mainly on the moist seaward slopes of the Coast Ranges, to southwestern Oregon, but seldom reaches more than 30 miles inland.

Fig. 30.-Redwood forest, California.

The redwood resembles the cedar in habit, general appearance, character of its wood, and colour of bark and leaves. It flourishes best in moist localities, and attains a great size, surpassing in height and diameter of stem even the giant firs of Washington, and is only exceeded on this continent by its cousin, the great sequoia (Sequoia gigantea) of the western slope of the Sierra Nevada, in south-central California. It frequently attains a height of 300 or more feet, with a diameter at the base of 15 or 16, and in certain exceptional instances of over 20 feet. It rarely branches low, but almost invariably has a straight, fluted stem, perfectly symmetrical, rising with a slight taper for about 200 feet to the first limb. The foliage is dull green in colour, fine, and drooping. It is a most beautiful tree both in form and colour, and is markedly gregarious in habit. As stated by Henry Gannett, it forms the densest forest known if the comparison is made on the basis of the amount of merchantable lumber growing on a given unit of area. For example, the yellow-pine forests of the Southern Atlantic and Gulf States contain on an average about 5,000 feet, board measure (square feet of boards an inch thick), of timber per acre, and in the moderately dense portion of the white-pine forests of the Great Lakes region the average is about the same. In each of these regions, famed for their lumber, a tract containing 10,000 feet of lumber per acre would be considered as heavily forested. In the redwood forests of California, however, 50,000 feet of lumber per acre is not rare over extensive areas, while for special tracts containing many square miles this estimate may safely be doubled. Upon 96,443 acres in Humboldt County, California, the average amount of lumber contained in the trees still standing is 84,000 feet per acre. The returns of lumber companies during a continuous period of ten years from tracts which have been cleared show a return of 75,000 to 100,000 feet per acre, but even this is not the maximum. A certain tract of several square miles actually yielded 150,000 feet per acre; and there is on record a yield of 1,431,530 feet from a single acre. One tree is said to have furnished 66,500 feet of lumber, and another, 15 feet in diameter at the base, contained 100,000 feet. Another tree, still standing, measures 22 feet in diameter, and it is estimated will yield 200,000 square feet of boards an inch thick.

The wood of the redwood-tree is of a clear red colour with the exception of a thin layer just under the bark, which is almost pure white, and is light, soft, coarse-grained, and susceptible of a high polish. It is the most common and most valuable of all the forest products of the Pacific coast of North America, and is serviceable for a great variety of purposes.

The celebrated "big trees" of California are not to be confounded with the redwood described above, but belong to a different species of the same genus. The big trees are worthy of their name, as they are by far the largest in North America. When full-grown they average about 275 feet in height, with a diameter near the ground of about 20 feet. One of the tallest as yet measured has a height of 325 feet, and the largest a diameter of 35 feet 8 inches inside the bark and 4 feet above the ground. The age of one of these giants, as shown by the number of rings of growth in its trunk, is about thirteen hundred years; another, 24 feet in diameter, is twenty-two hundred years old; and a third showed over four thousand rings of growth, and must have been in its prime at the time of the birth of Christ. The trees occur in detached groves on the western slope of the Sierra Nevada in south-central California, but become more common southward, where they form a genuine forest belt. Their range from north to south is about 260 miles, and their elevation above the sea from 6,000 to 8,000 feet.

"So exquisitely harmonious," says John Muir, in his charming book The Mountains of California, "and finely balanced are even the very mightiest of these monarchs of the woods in all their proportions and circumstances, that there is never anything overgrown or monstrous about them. On coming in sight of them for the first time, you are likely to say, 'Oh, see what beautiful, noble-looking trees are towering there among the firs and pines!' their grandeur being in the meantime in great part invisible, but to the living eye it will be manifest sooner or later, stealing slowly on the senses like the grandeur of Niagara or the lofty Yosemite domes. Their great size is hidden from the inexperienced observer as long as they are seen at a distance in one harmonious view. When, however, you approach them and walk around them, you begin to wonder at their colossal size and seek a measuring-rod. These giants bulge considerably at the base, but not more than is required for beauty and safety; and the only reason that this bulging seems in some cases excessive is that only a comparatively small section of the shaft is seen at once in near views. One that I measured in the King's River forest was 25 feet in diameter at the ground and 10 feet in diameter 200 feet above the ground, showing that the taper of the trunk as a whole is charmingly fine. And when you stand back far enough to see the massive columns from the swelling instep to the lofty summit dissolving in a dome of verdure, you rejoice in the unrivalled display of combined grandeur and beauty. About 100 feet or more of the trunk is usually branchless, but its massive simplicity is relieved by the bark furrows, which, instead of making an irregular network, run evenly parallel, like the fluting of an architectural column, and to some extent by tufts of slender sprays that wave lightly in the winds and cast flecks of shade, seeming to have been pinned on here and there for the sake of beauty only. The young trees have slender simple branches down to the ground, put on with strict regularity, sharply aspiring at the top, horizontal about half-way down, and drooping in handsome curves at the base. By the time the sapling is five or six hundred years old this spiry, feathery, juvenile habit merges into a firm, rounded dome form of middle age, which in turn takes on the eccentric picturesqueness of old age. No other tree in the Sierra forest has foliage so densely massed or presents outlines so firmly drawn and so steadily subordinate to a special type.... The foliage of the saplings is dark bluish green in colour, while the older trees ripen to a warm brownish-yellow tint, like Libocedrus. The bark is rich crimson brown, purplish in young trees and in shady portions of the old, while the ground is covered with brown leaves and burrs forming colour masses of extraordinary richness, not to mention the flowers and underbrush that rejoice about them in their season. Walk in the sequoia woods at any time of year, and you will say they are the most beautiful and majestic on earth. Beautiful and impressive contrasts meet you everywhere; the colours of tree and flowers, rock and sky, light and shade, strength and frailty, endurance and evanescence, tangles of supple hazel-bushes, tree pillars about as rigid as granite domes, roses and violets the smallest of their kind, blooming around the feet of the giants. Then in winter the trees themselves break forth in bloom, myriads of small four-sided staminate cones crowd the ends of the slender sprays, colouring the whole tree, and when ripe dusting the air and ground with golden pollen."

Owing to the remoteness of the big trees from commercial centres, they have escaped to a great extent the destruction which everywhere attends the advent of the white man, and some of the finest groves are now under state protection.

The sequoias are not only of interest on account of their great size and grandeur, but from the fact that they are the lingering survivors of an ancient and once widely distributed genus. During the Cretaceous and Tertiary divisions of geological history the genus numbered at least 50 species, as has been shown by leaf impressions, fossil wood, and cones buried in the rocks of New Zealand and Chile on the south, Spitzbergen and Greenland on the north. Over North America they extend from the Atlantic to the Pacific. At present the only two species known, both of which, as already stated, are confined to the Pacific coast, and with the exception of a slight extension of the less gigantic of the two into southwestern Oregon, are found only in California.

While the firs, cedars, and redwoods form the major portion of the forests in the more humid regions on the western side of the continent, there are two species of pines growing in drier situations which in a general view are even more characteristic of the Pacific forest than are the sequoias. These two pines, well worthy to stand side by side with the giant firs and still more gigantic redwoods, are known as the sugar-pine and the yellow pine.

The sugar-pine grows amid the mountains from southwestern British Columbia, southward through western Washington, Oregon, and on the Sierra Nevada and Coast Ranges of California, at elevations ranging from 4,000 to 8,000 feet. It frequently clothes steep declivities or bids defiance to the storms on the crests of sharp ridges. In size it is scarcely exceeded by any of its companions excepting the firs and sequoias. It frequently attains a height of from 200 to 275 feet, with a diameter at the base of from 8 to 14, and in some instances of over 20 feet. Individual trees are known which have a height of 245 feet and are 18 feet in diameter. The branches are usually high above the ground and widely spreading. In the case of well-grown individuals they leave the main trunk with a sweeping, downward curve, which midway out changes to an upward curve, and at the extreme distal end droops once more. At the extremity of many of the far-reaching boughs there are suspended one or two cones, each 12 or 14 inches long and sometimes over 8 inches in diameter. The peculiar and frequently remarkably regular curvature of the great branches, giving them the form of half a Cupid's bow, imparts to these mighty pines a grace and symmetry possessed by few other trees. The familiar name of this great pine refers to the fact that from wounds or incisions in its trunk there exudes a sweet sap which is considered by many persons to exceed even the sap of the maple in agreeableness of flavour.

Lovers of beautiful trees will agree in considering the sugar-pine as the noblest of its family growing in the woods of America, if not the most majestic of its kindred in the world. Its only rival, but of a different type of beauty, is the Norfolk Island pine, of the south sea islands.

Of the many pleasant memories of camp life in the forests of America which are a source of delight to the writer none are recalled with greater pleasure than those associated with the sugar-pine of the Sierra Nevada, where the ground is carpeted with the long brown needles that fall in showers at certain seasons from the boughs far overhead. With the faded leaves are strewed also the great cones which always excite wonder and admiration. In the clear air and brilliant sunlight of the Californian mountains the luxuriant plume-like leaves far aloft appear to be formed of burnished silver or have the yellow of gold, according as the light strikes them, and at night the lofty boughs swayed by the winds make music such as no other forest can produce. Nothing in the vegetable world, not even the great sequoias, convey such an abiding impression of strength and majesty as these pines which have withstood the storms of centuries without losing their vigour or their symmetry and beauty of form. Unfortunately as it would seem, however, these magnificent trees are useful, as the term is commonly employed, and are fast falling a prey to lumbermen, who measure their value in dollars.

The yellow pine of the Pacific mountains, not to be confounded, however, with the yellow pine of the southern Appalachian region, fortunately has another common name, the silver pine, which is more appropriate and distinctive. This is the most widely spread, perhaps, of all the pines of North America, and is familiar to every one who has travelled through the Pacific mountains from British Columbia to Mexico, and from the Black Hills of Dakota or the mountains of Colorado and New Mexico westward to within hearing of the surf of the Pacific Ocean. It ranks second in size to the sugar-pine, but is a near rival in strength and nobleness of form. As might be inferred from its wide distribution, the silver pine had adapted itself to a great range of conditions, not only of climate, but of soil and height above the sea. It is found from an elevation of about 2,000 feet above the sea up the mountainsides nearly to timber-line, and flourishes alike in the hot, arid valleys and in regions bordering on perpetual snow and ice. One beautiful feature of the silver-pine forests is their open, park-like character. The trees stand far apart, and thus have room to reach not only a great size, but a remarkable degree of perfection of form. Between the islands of shade on the sunlit ground there is usually but little undergrowth, and the far-extending natural pastures permit one to ride in any direction without inconvenience.

One other pine of the widely extended Pacific forest demands attention even from the passing traveller, not on account of its size, for it is a dwarf in a land of giants, but for its wide distribution and the food its large, oily seeds furnish for birds, squirrels, and even for man. I refer to the pi?on pine, of which there are several species. They are seldom over 35 or 40 feet high, and are not remarkable for beauty, although they furnish an agreeable feature in the sparsely forest-clothed and semiarid region where they thrive best, but they bear a profusion of small cones, each of which contains perhaps a dozen edible and nutritious seeds. These seeds were formerly used by the Indians for food on an extensive scale, and are still gathered in large quantities, and may be found in the markets of our cities. The Indian encampments in the pi?on forests in the fall of the year are among the most picturesque features of these degenerate days of the aborigines.

In the southwest portions of the United States the forests are confined to the mountains and the higher table-lands, the hot, arid valleys being without trees other than the larger growths of cacti and yucca. Similar conditions are present in northern Mexico, but on the western side of that republic and throughout practically the whole of the peninsula of Lower California the mountains and valleys alike are treeless and desolate.

As stated by C. S. Sargent, the forests of North America, exclusive of Mexico, Central America, and the West Indies, contain arboreal representatives of 158 genera of plants, of which 94 genera occur in the Atlantic and 59 in the Pacific side of the continent, and 48 genera in the tropical portion of southern Florida. Of the number of genera of trees in the Caribbean forest we have no reliable census.

PRAIRIES, TREELESS PLAINS, AND PLATEAUS

To the west of the Atlantic forest lie the broad natural meadows termed prairies, and still farther west the yet more extensive pasture-lands of the great plateaus which reach the eastern base of the Rocky Mountains (Fig. 28). The transition from the luxuriant and varied forest on the east to the treeless, thinly grass-covered plateaus on the west side of the interior Continental basin is gradual. The change occurs in the prairie region, where a struggle has been in progress for thousands of years between the conditions favouring and those adverse to tree growth. The balance of power, so to speak, is the amount of rain or of soil-stored moisture during the summer season. The gradual decrease in the mean annual precipitation from east to west on the inland border of the Atlantic forest continues westward, and on the plateaus adjacent to the Rocky Mountains the aridity is such that no trees can grow except along the immediate border of the stream, unless artificially irrigated.

The explanation of the absence of trees in the central and western portions of the interior Continental basin is found in the mean annual rainfall and the manner in which it is distributed throughout the year, together with variations in the texture and composition of the soil, and the disturbances in the natural conditions brought about by fires. The question, "Why are the prairies treeless?" has been variously answered by different observers. The outcome of a long discussion in this connection seems to be that the main cause of the absence of trees lies in the climatic conditions and principally in the lack of sufficient rain during the long, hot summers. Arid regions the world over are without forests, but the Prairie plains cannot be said to be arid; in fact, the mean annual rainfall over the greater portion of this region is equal to or exceeds that of many well-forested countries, averaging as it does in general about 30 inches. But the prairies lie between the more humid forest-covered regions on the east and the less humid or subarid plateaus on the west, and during the summer season droughts and hot, scorching winds are of common occurrence. It is the long dry summer that establishes the critical conditions, particularly about the eastern and northern borders of the prairies. Of secondary importance is the character of the soil. An exceedingly fine soil, like that of the prairies, as has been pointed out by J. D. Whitney, by excluding the air from the roots of trees is detrimental to their growth. Where the dryness of the summers make the lives of trees precarious the nature of the soil, whether coarse or fine, becomes the controlling factor. In the prairie region where the soil is more open and porous than usual, although other conditions remain the same, as in the Cross Timbers of Texas, trees flourish; while intervening areas where the soil is fine are typical prairies. Again, where the climatic conditions become critical, as during long, dry summers, the grass and other vegetation burns readily, fire spreads rapidly and widely, and young trees are destroyed. In the prairie region, as pointed out by J. W. Powell, the Indians were formerly in the habit of burning the grass each summer in order to insure more favorable pasturage for game during the succeeding spring. This annual burning kept back the forest and led to the eastward extension of the prairie.

During the past decade many groves have been planted on the prairies, and have flourished, especially when the adjacent fields are cultivated so as to allow the earth to store a larger share of the winter rain; the success of this tree planting, it has been claimed, is evidence that the nature of the soil is not a determining factor in the problem, because trees will grow if protected from fire. The success of arboriculture on the formerly treeless plains and plateaus, however, decreases as one travels westward. On the western border of the prairies and on the great plateaus, remote from streams, trees can be made to grow only by the aid of irrigation. If this region had never been swept by fire it is safe to say it would still be treeless. Each of the explanations referred to above to account for the treeless condition of the prairies-one referring it to soil conditions, and the other to the former prevalence of fires-certainly has much in its favour, and for certain localities seems satisfactory, but each point of view should include a broader range and recognise the fact that the requisite critical conditions have been furnished by wide-reaching climatic causes. The Prairie plains furnish but one phase of the gradual change that occurs in the natural mantle of vegetation when traced from the dense, well-watered forests of the Appalachians and the Alleghany plateau westward to the semiarid and truly arid lands of the great plateaus and Rocky Mountain region, where only such plants as are able to withstand long-continued drought can grow. This same broad conclusion is sustained also at the north, where the prairie dovetails, as it were, with the subarctic forest.

The general or underlying reason for the treeless condition of the vast central portion of the continent is doubtless a lack of sufficient rain. The precipitation that does occur comes mainly during the winter season, when the land is colder than the ocean; in summer the land becomes highly heated and imparts its temperature to the air, which thus has its capacity for moisture increased, and prolonged droughts occur. At the south, in Mexico and the adjacent portion of the United States, the trade-winds blow over a region which is more highly heated than the ocean from which they come, and are hence drying winds. To the west of the Great plateaus rise the Rocky Mountains, where climatic conditions are different on account of elevation, and, as we have seen, forests occur at considerable elevations, but not in the broader valleys. The conditions unfavourable for tree growth are continued and even intensified in the valleys of the central portion of the Pacific mountain region, and culminate in the deserts of the Great Basin and western Mexico. Throughout all of this vast treeless region the controlling condition is deficiency of moisture, particularly during the summer or growing season.

The nearest approach to desert conditions to be found in North America occur in the valley of Utah and Nevada and the southern portion of the Great Basin region in Arizona and Mexico. The bottoms of these valleys are, in some instances, occupied by shallow lakes in winter, when scanty rains occur, but during the long, hot summers they become completely desiccated, and are then broad expanses of hard mud, cracked by drying so as to resemble a tessellated pavement of cream-coloured marble. These mud-flats or playas are frequently absolutely without plant life. Excepting the playas, however, and, in numerous instances, a narrow belt of ground encircling them, which is white with efflorescent salts, the valleys of even the most arid portion of the Great Basin region are generally plant-covered. The most common and most widely spread of the shrubs on these shadeless plains is the sage-brush. So characteristic is this plant of countless valleys from Canada to Mexico within the general region of the Pacific mountains that to one familiar with the country the term "sage-brush land" brings to mind the leading features of the region designated. The sage-brush lands are far from being desert areas, however, for in early spring a profusion of low, sweet-scented flowers bloom beneath the gray-green Artemisia, and sufficient bunch-grass to sustain considerable herds may be expected in the same localities.

The vast, irregular belt of forest encircling the central treeless portion of the continent also dies out on its northern border, where the subarctic forest is succeeded northward by the Barren Grounds and tundra plains. Clearly the explanation of the absence of trees in the prairie region and the adjacent plateaus cannot be applied to scarcely less extensive treeless plains at the far north, where rain falls in summer and the soil is always abundantly charged with moisture. It needs no argument to show that the control among the conditions governing tree growth at the north passes to the temperate element of climate, and that the timber-line is there determined, as it is on high mountains, by the severity of the winters' storms and frosts and the shortness of the summers.

THE TREELESS MOUNTAIN TOPS

On the higher mountains of North America above the upper limit at which trees are able to grow there are picturesque regions carpeted and garlanded in late spring and summer with lovely flowers, the indescribable charms of which are only known to those who rejoice in climbing rugged peaks and in following the trails of the mountain-goat along sharp-crested ridges. The gorgeous blossoms of these roof-gardens of the world are much the same on all high mountains in temperate latitudes, but from having become first widely known to civilized man on the mountains of Switzerland, are generally termed alpine flowers. The most attractive features of an alpine flora, which springs into bloom as soon as the snow melts and forms a rapidly widening belt of colour as the margins of the snow-fields recede higher and higher, is the great profusion of brilliantly coloured blossoms. No sooner does the snow of winter melt than the moist ground becomes enamelled in brilliant colours on account of the springing up and quick blossoming of millions of hardy plants. The growing season on mountain heights is short, but the sun's energy is there more intense and the hours of light each day longer than in the valleys below, and the plants adapted to such conditions pass through their annual circle of changes from sprouting seed to mature fruit with remarkable rapidity. In many instances the mountain-climber finds beautiful lilies unfolding their sun-dyed blossoms at the bottom of well-like depressions in lingering snow-banks. The gleaming mountain-peaks when seen from afar are said to be crowned with snow, but the mountaineer rejoices in the knowledge that their cold diadems are wreathed and festooned about their lower margins with lovely blossoms. Many mountains less ambitious than their neighbours have the garlands without the crown. An alpine flora is present on the Pacific mountains from Mexico northward to Alaska. Like the "timber-line" and the "snow-line," the intermediate belt of profusely flowering herbaceous plants descends lower and lower with decrease in latitude; on the great volcanic cones of Mexico it has an elevation of over 15,000 feet; on the Sierra Nevada the greatest wealth of flowers occurs at about 12,000 feet; on Mount Rainier widely extended gardens resplendent with rainbow tints occur at 7,000 to 8,000 feet; and about the foot-hills near Mount St. Elias, at an elevation of 2,500 feet or less above the sea, every knoll and island-like area in the vast ice-fields is so densely overgrown with brilliantly flowered plants that one has to part the rank growths with his hands and press them aside with his alpenstick in order to force a way through the fields of bloom. Admirers of nature's loveliness who have not climbed to aspiring heights will find a new and beautiful world in the public alpine garden on the summit and about the snow-fields of the higher portions of the Pacific mountains, where no sign-boards forbid entry and no fences obstruct the way. In these regions nearest the sun and stars there are few, if any, plants of utility to man, but marvellous beauty and lavish profusion fill the foreground in every view. These glorious mountain heights have their use, however, although as yet known to but few; rest and recreation amid scenes at the same time novel and most inspiring may there be found by the toilers in our crowded cities.

Among the Atlantic mountains only a few summits attain a sufficient elevation to claim a wreath of alpine flowers. Something of the nature of the gorgeous fields of bloom about the great peaks of the Pacific mountains is suggested on the treeless summits of the White Mountains, but although classed by botanists among alpine floras, the plants growing there fail to give a true idea of the display characteristic of the mountains which make a nearer approach to the lower limit of perennial snow. In the southern Appalachians the absence of a luxuriant alpine flora is perhaps more than counterbalanced by the profusion of rhododendrons, azaleas, and laurels.

One instructive lesson suggested by this hasty glance at the plant life of North America is furnished by the quick response that vegetation gives to conditions of environment. Throughout the greater divisions of the forest, prairies, grass-covered plains and valleys, and flower-decked mountain heights there are constant variations from locality to locality in the plant life to meet seemingly obscure or but slight changes in the conditions of temperature, humidity, exposure to sunlight, soil composition, soil texture, etc.; and besides there is a never-ceasing struggle for existence among the plants themselves which leads to important modifications of a flora. These changes occur from locality to locality, frequently within a short radius, but more than this, the resultant of the various modifying conditions on which plant life depends are not constant even for a given locality. The study of extinct floras has shown that during the preceding ages in the earth's history marvellous changes in the plants of many regions, and, in fact, of the entire earth's surface, have taken place. The distinct impressions of palm-leaves, for example, are commonly found in the rocks of the Cascade Mountains, where spruces, firs, and cedars now dominate the landscape. Still more striking is the fact that even treeless Greenland and the largely ice-covered islands of the arctic archipelago were formerly clothed with forests as luxuriant and varied as those now growing in the southern Appalachian region. Although the migrations of existing forests during the few centuries of which we have historic records have been too slow to be appreciated by man, yet it is safe to conclude that changes similar to, and in fact a continuation of, those known by geologists to have taken place in the distribution of the vegetation of the continent since the Tertiary period are still in progress. With far-reaching and exceedingly slow changes in climatic conditions and in elevation above the sea due to upheaval and denudation, the plants of our forests, prairies, and mountainsides, are being moved here and there, in ever-changing combinations. Nature thus secures a rotation in the vegetation of a region, as the careful husbandman varies his crops from year to year. The suggestion in this connection furnished by geologists is that we are living in a spring-time following the great winter, known as the Glacial epoch, and that the tropical, temperate, and subarctic forests are migrating northward in an orderly march, and each in turn ascending higher and higher on the more lofty mountains.

LITERATURE

Muir, John. The Mountains of California. T. Fisher Unwin, London, 1894.

Pinchot, Gifford. A Primer of Forestry. United States Department of Agriculture, Bulletin No. 24, Washington, D. C., 1899.

Sargent, C. S. Report on the Forests of North America. Tenth Census of the United States, vol. ix, Washington, D. C., 1884.

United States Geological Survey. Reports on Forestry.

* * *