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[Illustration: HENRY H. GIBSON]


AMERICAN FOREST TREES

by

HENRY H. GIBSON

Edited by Hu Maxwell







Hardwood Record
Chicago
1913

Copyright 1913 by
Hardwood Record
Chicago, Ill.

The Regan Printing House
Chicago.




PREFACE


The material on which this volume is based, appeared in Hardwood Record,
Chicago, in a series of articles beginning in 1905 and ending in 1913,
and descriptive of the forest trees of this country. More than one
hundred leading species were included in the series. They constitute the
principal sources of lumber for the United States. The present volume
includes all the species described in the series of articles, with a
large number of less important trees added. Every region of the country
is represented; no valuable tree is omitted, and the lists and
descriptions are as complete as they can be made in the limited space of
a single volume. The purpose held steadily in view has been to make the
work practical, simple, plain, and to the point. Trees as they grow in
the forest, and wood as it appears at the mill and factory, are
described and discussed. Photographs and drawings of trunk and foliage
are made to tell as much of the story as possible. The pictures used as
illustrations are nearly all from photographs made specially for that
purpose. They are a valuable contribution to tree knowledge, because
they show forest forms and conditions, and are as true to nature as the
camera can make them. Statistics are not given a place in these pages,
for it is no part of the plan to show the product and the output of the
country's mills and forests, but rather to describe the source of those
products, the trees themselves. However, suggestions for utilization are
offered, and the fitness of the various woods for many uses is
particularly indicated. The prominent physical properties are described
in language as free as possible from technical terms, and yet with
painstaking accuracy and clearness. Descriptions intended to aid in
identification of trees are given; but simplicity and clearness are held
constantly in view, and brevity is carefully studied. The different
names of commercial trees in the various localities where they are
known, either as standing timber or as lumber in the yard and factory,
are included in the descriptions as an assistance in identification. The
natural range of the forest trees, and the regions where they abound in
commercial quantities, are outlined according to the latest and best
authorities. Estimates of present and future supply are offered, where
such exist that seem to be authoritative. The trees are given the common
and the botanical names recognized as official by the United States
Forest Service. This lessens misunderstanding and confusion in the
discussion of species whose common names are not the same in different
regions, and whose botanical names are not agreed upon among scientific
men who mention or describe them. The forests of the United States
contain more than five hundred kinds of trees, ranging in size from the
California sequoias, which attain diameters of twenty feet or more and
heights exceeding two hundred, down to indefinite but very small
dimensions. The separating line between trees and shrubs is not
determined by size alone. In a general way, shrubs may be considered
smaller than trees, but a seedling tree, no matter how small, is not
properly called a shrub. It is customary, not only among botanists, but
also among persons who do not usually recognize exact scientific terms
and distinctions, to apply the name tree to all woody plants which
produce naturally in their native habitat one main, erect stem, bearing
a definite crown, no matter what size they may attain.

The commercial timbers of this country are divided into two classes,
hardwoods and softwoods. The division is for convenience, and is
sanctioned by custom, but it is not based on the actual hardness and
softness of the different woods. The division has, however, a scientific
basis founded on the mechanical structures of the two classes of woods,
and there is little disagreement among either those who use forest
products or manufacture them, or those who investigate the actual
structure of the woods themselves, as to which belong in the hardwood
and which in the softwood class.

_Softwoods_--The needleleaf species, represented by pines, hemlocks,
firs, cedars, cypresses, spruces, larches, sequoias, and yews, are
softwoods. The classification of evergreens as softwoods is erroneous,
because all softwoods are not evergreen, and all evergreens are not
softwoods. Larches and the southern cypress shed their leaves yearly.
Most other softwoods drop only a portion of their foliage each season,
and enough is always on the branches to make them evergreen. Softwoods
are commonly called conebearers, and that description fits most of them,
but the cedars and yews produce fruit resembling berries rather than
cones. Though the needleleaf species are classed as softwoods, there is
much variation in the absolute hardness of the wood produced by
different species. The white pines are soft, the yews hard, and the
other species range between. If there were no other means of separating
trees into classes than tests of actual hardness of wood, the line
dividing hardwoods from softwoods might be quite different from that now
so universally recognized in this country.

_Hardwoods_--The broadleaf trees are hardwoods. Most, but not all, shed
their foliage yearly. It is, therefore, incorrect to classify deciduous
trees as hardwoods, since it is not true in all cases, any more than it
is true that softwoods are evergreen. Live oaks and American holly are
evergreen, and yet are true hardwoods. In a test of hardness they stand
near the top of the list.

There are more species of hardwoods than of softwoods in this country;
but the actual quantity of softwood timber in the forests greatly
exceeds the hardwoods. Nearly two hundred species of the latter are
seldom or never seen in a sawmill, while softwoods are generally cut and
used wherever found in accessible situations.

As in the case of needleleaf trees, there is much variation in actual
hardness of the wood of different broadleaf species. Some which are
classed as hardwoods are softer than some in the softwood list. It is
apparent, therefore, that the terms hardwood and softwood are commercial
rather than scientific.

Palm, cactus, and other trees of that class are not often employed as
lumber, and it is not customary to speak of them as either hardwoods or
softwoods.

_Sapwood and Heartwood_--Practically all mature trees contain two
qualities of wood known as sap and heart. The inner portion is the
heartwood, the outer the sap. They are usually distinguished by
differences of color.

The terms are much used in lumber transactions and are well understood
by the trade. The two kinds of wood need be described only in the most
general way, and for the guidance and information of those who are not
familiar with them. Differences are many and radical in the relative
size and appearance of the two kinds of wood in different species, and
even between different trees of the same species. No general law is
followed, except that the heartwood forms in the interior of the tree,
and the sapwood in a band outside, next to the bark. In the majority of
cases young trees have little heartwood, often none. It is a development
attendant on age, yet age does not always produce it. Some mature trees
have no heartwood, others very little.

The two kinds of wood belong to needleleaf and broadleaf trees alike;
but palms, owing to their manner of growth, have neither. Their size
increases in height rather than in diameter. With palms, the oldest wood
is in the base of the trunk, the newest in the top; but in the ordinary
timber tree the oldest wood is in the center of the trunk, the youngest
in the outside layers next the bark. It is the oldest that becomes
heartwood, and it is, of course, in the center of the tree. The band of
sapwood is of no certain thickness, but averages much thicker in some
species than in others. The sapwood of Osage orange is scarcely half an
inch thick, and in loblolly pine it may be six inches or more.

Heartwood is known by its color. The eye can detect no other difference
between it and the surrounding band of sapwood. There is no fundamental
difference. The heart was once sapwood, and the latter will sometime
become heartwood if the tree lives long enough. As the trunk increases
in size and years, the wood near the heart dies. It no longer has much
to do with the life of the tree, except that it helps support the weight
of the trunk. The heartwood is, therefore, deadwood. The activities of
tree life are no longer present. The color changes, because mineral and
chemical substances are deposited in the wood and fill many of the
cavities. That process begins at the center of the trunk and works
outward year by year, forming a pretty distinct line between the living
sapwood and the dead and inert heartwood.

For some reason, the heartwood of certain species is prone to decay.
Sycamore is the best example. The largest trunks are generally hollow.
The heart has disappeared, leaving only the thin shell of sapwood, and
this is required not only to maintain the tree's life and activities,
but to support the trunk's weight. In most instances the substances
deposited in the heartwood, and associated with the coloring matter,
tend to preserve the wood from decay. For that reason heart timber lasts
longer than sap when exposed in damp situations. The dark and variegated
shades of the heartwood of some species give them their chief value as
cabinet and furniture material. The sapwood of black walnut is not
wanted by anybody, for it is light in color and is characterless; but
when the sap has changed to heart, and its tones have been deepened by
the accumulation of pigments, it becomes a choice material for certain
purposes. The same is true of many other timbers, notably sweet and
yellow birch, black cherry, and several of the oaks.

It sometimes happens that when sapwood is transformed into heart, a
physical change, as well as a coloring process, affects it. Persimmon
and dogwood are examples, and hickory in a less degree. The sapwood of
persimmon and dogwood makes shuttles and golf heads, but after the
change to heartwood occurs, it is considered unsuitable. Handle makers
and the manufacturers of buggy spokes prefer hickory sapwood, but use
the red heartwood if it is the same weight as the sap.

_Annual Rings_--The trunks of both hardwoods and softwoods are made up
of concentric rings. In most instances the eye easily detects them. They
are more distinct in a freshly cut trunk than in weathered wood, though
in a few instances weathering accentuates rather than obliterates them.
A count of the rings gives the tree's age in years, each ring being the
growth of one year. An occasional exception should be noted, as when
accident checks the tree's growth in the middle of the season, and the
growth is later resumed. In that case, it may develop two rings in one
year. A severe frost late in spring after leaves have started may
produce that result; or defoliation by caterpillars in early summer may
do it. Perhaps not one tree in a thousand has that experience in the
course of its whole life. Trees in the tropics where seasons are nearly
the same the year through, seldom have rings. Imitations of mahogany are
sometimes detected by noting clearly marked annual rings. It is
difficult for the woodfinisher to obliterate the annual rings, but some
of the French woodworkers very nearly accomplish it.

No law of growth governs the width of yearly rings, but circumstances
have much to do with it. When the tree's increase in size is rapid,
rings are broad. An uncrowded tree in good soil and climate grows much
faster than if circumstances are adverse. Carolina poplar and black
willow sometimes have rings nearly three-fourths of an inch broad, while
in the white bark pine, which grows above the snow line in California,
the rings may be so narrow as to be invisible to the naked eye.

There is no average width of yearly rings and no average age of trees. A
few (very few) of the sequoias, or "big trees" of California, are two
thousand years old. An age of six or seven centuries appears to be about
the limit of the oldest of the other species in this country, though an
authentic statement to that effect cannot be made. There are species
whose life average scarcely exceeds that of men. The aspen generally
falls before it is eighty; and fire cherry scarcely averages half of
that. Of all the trees cut for lumber, perhaps not one in a hundred has
passed the three century mark. That ratio would not hold if applied to
the Pacific coast alone.

_Spring and Summerwood_--These are not usual terms with lumbermen and
woodworkers, but belong more to the engineer who thinks of physical
properties of timber, particularly its strength. Yet, sawmill and
factory men are well acquainted with the two kinds of wood, but they are
likely to apply the term "grain" to the combination of the two.

Spring and summerwood make the annual ring. Springwood grows early in
the season, summerwood later. In fact, it usually is the contrast in
color where the summerwood of one season abuts against the springwood of
the next which makes the ring visible. The inside of the ring--that
portion nearest the heart of the tree--is the springwood, the rest of
the ring is the summerwood. The former is generally lighter in color.
Sometimes, and with certain species, the springwood is much broader than
the other. The summerwood may be a very narrow band, not much wider than
a fine pencil mark, but its deeper color makes it quite distinct in most
instances. In other instances, as with some of the oaks, the summerwood
is the wider part of the annual ring. The figure or "grain" of southern
yellow pine is largely due to the contrast between the dark summerwood
and light springwood of the rings. The same is true of ash, chestnut,
and of many other woods.

_Pores_--Wood is not the solid substance it seems to be when seen in the
mass. If magnified it appears filled with cavities, not unlike a piece
of coral or honeycomb; but to the unaided eye only a few of the largest
openings are visible, and in some woods like maple, none can be seen.
The large openings are known as pores. They are so prominent in some of
the oaks that in a clean cut end or cross section they look like pin
holes. Very little magnifying is required to bring them out distinctly.
A good reading glass is sufficient.

Pores belong to hardwoods only. The resin ducts in some softwoods
present a similar appearance, but are far less numerous. All pores are,
of course, situated in the annual rings, but in different species they
are differently located as to spring and summerwood. In some woods the
largest pores are in the springwood only and therefore run in rings.
Such woods are called "ring porous," and the oaks are best examples. In
other species the pores are scattered through all parts of the ring in
about the same proportion, and such woods are called "diffuse porous,"
as the birches. Softwoods have no pores proper, and are classed
"non-porous."

_Medullary Rays_--A smoothly-cut cross section of almost any oak, but
particularly white oak and red oak, exhibits to the unaided eye narrow,
light- lines radiating from the center of the tree toward the
bark like spokes of a wheel. They are about the breadth of a fine pencil
mark, and are generally a sixth of an inch or less apart. They are among
the most conspicuous and characteristic features of oak wood, and are
known as medullary or pith rays.

Oak is cited as an example because the rays are large and prominent, but
they are present in all wood, and constitute a large part of its body.
They vary greatly in size. In some woods a few are visible unmagnified;
but even in oak a hundred are invisible to the naked eye to one that can
be seen. Some species show none until a glass is used. Some pines have
fifteen thousand to a square inch of cross section, all of which are so
small as to elude successfully the closest search of the unaided eye.

The medullary rays influence the appearance of most wood. They determine
its character. Oak is quarter-sawed for the purpose of bringing out the
bright, flat surfaces of these rays. The prominent flecks, streaks, and
patches of silvery wood are the flat sides of medullary rays. In cross
section, only the line-like ends are seen, but quarter-sawing exposes
their sides to view.

That explains in part why some species are adapted to quarter-sawing and
others are not. If no broad rays exist in the wood, as with white pine,
red cedar, and cottonwood, quarter-sawing cannot add much to the wood's
appearance.

_Grain_--The grain of wood is not a definite quality. The word does not
mean the same thing to all who use it. It sometimes refers to rings of
yearly growth, and in that sense a narrow-ringed wood is fine grained,
and one with wide rings is coarse grained. A curly, wavy, smoky, or
birdseye wood does not owe its quality to annual rings, yet with some
persons, all of these figures are called grain. The term sometimes
refers to medullary rays, again to hardness, or to roughness. Some
mahogany is called "woolly grained" because the surface polishes with
difficulty. The pattern maker designates white pine as "even grained",
because it cuts easily in all directions. The handle maker classes
hickory as "smooth grained", because it polishes well and the sole idea
of the maker is smoothness to the touch. There are other grains almost
as numerous as the trades which use wood. In numerous instances "figure"
is a better term than "grain." Feather mahogany, birdseye birch, burl
ash, are figures rather than grains. There is no authority to settle and
decide what the real meaning of grain is in wood technology. It has a
number of meanings, and one man has as much authority as another to
interpret it in accordance with his own ideas, and the usage in his
trade. It is a loose term which covers several things in general and
nothing in particular.

_Weight_--The weight of wood is calculated from different standpoints.
It has a green weight, an air-dry weight, a kiln-dry weight, and an
oven-dry weight. All are different, but the differences are due to the
relative amounts of water weighed. Sawlogs generally go by green weight;
yard lumber by air-dry or partly air-dry weight; while the wood used in
ultimate manufacture, such as furniture, is supposed to be kiln-dry.

The absolute weight of wood, with all air spaces, moisture, and other
foreign material removed, is about 100 pounds per cubic foot, which is
1.6 times heavier than water; but that is not a natural form of wood. It
is known only in the laboratory.

The actual wood substance of one species weighs about the same as
another. Dispense with all air spaces, all water, and all other foreign
substance, and pine and ebony weigh alike. It is apparent that the
different weights of woods, as between cedar and oak for example, are
due chiefly to porosity. The smaller the aggregate space occupied by
pores and other cavities, the heavier the wood. That accounts for the
differences in weights of absolutely dry woods of different kinds,
except that a small amount of other foreign material may remain after
water has been driven off. Florida black ironwood is rated as the
heaviest in the United States, and it weighs 81.14 pounds per cubic
foot, oven-dry. The lightest in this country is the golden fig which is
a native of Florida also. It weighs 16.3 pounds per cubic foot,
oven-dry. When weights of wood are given, the specimen is understood to
be oven-dry, unless it is stated to be otherwise: it is a laboratory
weight, calculated from small cubes of the wood. Such weights are always
a little less than that of the dryest wood of the same kind that can be
obtained in the lumber market.

_Moisture in Wood_--The varying weights of the same wood indicate that
moisture plays an important part. No man ever saw absolutely dry wood.
If heated sufficiently to drive off all the moisture, the wood is
reduced to charcoal and other products of destructive distillation.

The pores and other cavities in green timber are more or less filled
with water or sap. This may amount to one-third, one-half, or even more,
of the dry weight of the wood. The water is in the hollow vessels and
cell walls. A living tree contains about the same quantity of water in
winter as in summer, though the common belief is otherwise. It is
misleading to say that the sap is "down" in one season and "up" in
another, although there is more activity at certain times than in
others. Strictly speaking, there is a difference between the water in a
tree, and the tree's sap; but in common parlance they are considered
identical. What takes place is this: water rises from the tree's roots,
through the wood, carrying certain minerals in solution. Some of it
reaches the leaves in summer where it mixes with certain gases from the
air, and is converted into sap proper. Most of the surplus water, after
giving up the mineral substance held in solution, is evaporated through
the leaves into the air; but the sap, starting from the leaves which act
as laboratories for its manufacture, goes down through the newly-formed
(and forming), layer of wood just beneath the bark, and is converted
into wood. This newly-formed wood is colorless at first. It builds up
the annual ring, first the springwood very rapidly, and then the
summerwood more slowly.

The force which causes water to rise through the trunk of a tree is not
fully understood. It is one of nature's mysteries which is yet to be
solved. Forces known as root pressure, capillary attraction, and
osmosis, are believed to be active in the process, but there seems to be
something additional, and no man has yet been able to explain what it
is.

The seasoning of wood is the process of getting rid of some of the
water. As soon as lumber is exposed to air, the water begins to escape.
Long exposure to dry air takes out a large percentage of the moisture
which green wood holds, and the lumber is known as air-dry. But some of
the original moisture remains, and air at climatic temperature is unable
to expel it. The greater heat of a drykiln drives away some more of it,
but a quantity yet remains. The lumber is then kiln-dry. Greater heat
than the drykiln's is secured in an oven, and a little more of the
wood's moisture is expelled; but the only method of driving all the
moisture out is to heat the wood sufficiently to break down its
structure, and reduce it to charcoal.

Wood warps in the process of drying unless it seasons equally on all
sides. It curls or bends toward the side which dries most rapidly. Dry
wood may warp if exposed to dampness, if one side is more exposed and
receives more moisture than another. It curls or bends toward the dryer
side.

Warping is primarily due to the more rapid contraction or expansion of
wood cells on one side of the piece than on the other. Saturated cells
are larger than dry ones.

Moisture in wood affects its strength, the dryer the stronger, at least
within certain limits. Architects and builders carefully study the
seasoning of timber, because it is a most important factor in their
business. The moisture which most affects a wood's strength is that
absorbed in the cell walls, rather than that contained in the cell
cavities themselves.

Some woods check or split badly in seasoning unless attended with
constant care. Checking is due chiefly to lack of uniformity in
seasoning. One part of the stick dries faster than another, the dryer
fibers contract, and the pull splits the wood. The checks may be small,
even microscopic, or they may develop yawning cracks such as sometimes
appear in the ends of hickory and black walnut logs. Greenwood checks
worse in summer than in winter, because the weather is warmer, the
wood's surface dries faster, and the strain on the fibers is greater.
Phases of the moon have no influence on the seasoning, checking,
warping, or lasting properties of timber.

_Stiffness, Elasticity, and Strength_--Rules for measuring the stiffness
of timber are involved in mathematical formulas; but the practical
quality of stiffness is not difficult to understand. Wood which does not
bend easily is stiff. If it springs back to its original position after
the removal of the force which bends it, the wood is elastic. The
greatest load it can sustain without breaking, is the measure of its
strength. The load required to produce a certain amount of bending is
the measure of its stiffness. Flexibility, a term much used by certain
classes of workers in wood, is the opposite of stiffness. A brittle wood
is not necessarily weak. It may sustain a heavy load without breaking,
but when it fails, the break is sudden and complete. A tough wood
behaves differently, though it may not be as strong as a brittle one.
When a tough wood breaks, the parts are inclined to adhere after they
have ceased to sustain the