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.
[Illustration: 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-vitae, 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.
[Illustration: 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.
[Illustration: 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 pinyon 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 pinyon 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.