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[Illustration: A SOUTHERN MICHIGAN WOODLOT]
UNIVERSITY BULLETIN
NEW SERIES, SEPTEMBER, 1915 VOL. XVII, NO. 10
UNIVERSITY OF MICHIGAN
BOTANICAL GARDEN AND ARBORETUM
MICHIGAN TREES
A HANDBOOK OF THE NATIVE AND MOST
IMPORTANT INTRODUCED SPECIES
_By_
CHARLES HERBERT OTIS, FORMERLY CURATOR
WITH AN INTRODUCTION BY
GEORGE PLUMER BURNS, FORMERLY DIRECTOR
[Illustration]
Ann Arbor
PUBLISHED BY THE REGENTS
1915
COPYRIGHT, 1915
BY
THE REGENTS OF THE UNIVERSITY OF MICHIGAN
THIRD EDITION, REVISED
THE ANN ARBOR PRESS, PRINTERS
ANN ARBOR, MICH.
TABLE OF CONTENTS.
PAGE
A Southern Michigan Woodlot--_Frontispiece_.
Map of Michigan (Showing Details Mentioned in the
Bulletin) iv
Introduction v
Acknowledgments vii
How to Study the Trees ix
Artificial Keys, How Made and Used xviii
Summer Key to the Genera xxi
Winter Key to the Genera xxvii
Manual of Trees (Description of Species, with Summer
and Winter Keys to the Species) xxxiii
Glossary 231
Index to the Artificial Keys 241
Index to the Trees 242
[Illustration: MAP OF MICHIGAN
SHOWING ONLY LOCATIONS MENTIONED IN THE MANUAL]
INTRODUCTION
The idea of a bulletin on Michigan trees was first suggested by Prof.
Volney M. Spalding. It was thought that a bulletin devoted entirely to
the study of certain phases of tree life in Michigan would stimulate
interest in the study of our trees, and influence many more people to
associate themselves with the growing number of tree lovers and with the
supporters of the movement for better forest conditions in the state.
The bulletin has been under consideration for a number of years and much
of the material given herein has been used in the classes in forest
botany at the University of Michigan. It remained, however, for the
present Curator of the Botanical Garden and Arboretum to get the
material into shape for publication, and the present bulletin is the
result of his industry and perseverance. The preparation of the drawings
and manuscript has been made by him in connection with his work in the
Garden.
The distinctive feature of the bulletin lies in its keys. The keys
commonly published are based upon characters which are present but a
short time during the year, or which can be used only by an advanced
student of botany. This bulletin presents two keys. One is based upon
characters which are present all summer; the other uses the winter
characters as a basis for identification. By the use of the keys any
person should be able to name and learn the characteristics of the trees
of Michigan at any time of the year. These keys should prove of special
value to our students in the public schools, to members of nature study
clubs, and to the students in the forestry schools of the state.
The order of arrangement and the nomenclature are essentially those of
"Gray's New Manual of Botany." Following a tendency which is steadily
gaining favor, all species names are printed with a small letter,
regardless of their origin. For the convenience of the general reader,
other scientific names which are found in botanical manuals _in common
use_ are printed in parenthesis. In the case of exotics which are not
included in the Manual, other authorities have been followed. Sudworth's
"Check List of the Forest Trees of the United States" (U. S. Dept. Agr.,
Div. Forestry, Bul. 17) is in most cases authority for the common names.
They are names appearing in common use today in some part of the state.
The first name given is that recommended by Sudworth for general use.
The drawings have been made from living or herbarium material and are
original. They are accurately drawn to a scale, which is given in each
case. In their preparation the author has endeavored to call attention
to the salient characters. In the drawings of buds and twigs certain
points, bundle-scars, etc., have been emphasized more than is natural.
In the descriptions the attempt has been made to bring out those points
of similarity and contrast which are most useful for identification.
As the bulletin is not written especially for technical students of
botany, the author thought best to use as few technical terms as
possible in the descriptions. In some cases it was impossible to avoid
such terms, but with the help of the glossary the meaning can be easily
understood. Any person desiring to get a more complete knowledge of
trees should consult one of the larger manuals. The arrangement used for
the illustration and discussion of each single tree makes it possible
for the student to compare the drawings with the description without
turning a page.
It is believed that with the aid of the drawings and descriptions given
in this bulletin any person will be able to name the trees which grow in
his yard, park, or woodlot. If, however, any difficulty is found in
naming the trees, the Curator will be glad to name any specimens which
may be mailed to him. He would be glad to get in touch with persons
interested in Michigan trees and to receive any additional information
relating to the subject. Data concerning the distribution of the trees
in the state, and the addition of other Michigan trees to the present
list would be of especial value.
GEORGE PLUMER BURNS.
ACKNOWLEDGMENTS
Grateful acknowledgment is hereby made to Miss Sarah Phelps, who has
done most of the inking in and given life to the author's
pencil-drawings; to Mr. J. H. Ehlers for his valuable assistance in the
preparation of many of the drawings and in the collection of working
material; to Prof. Henri Hus, who has read all of the proof and who has
at various times rendered valuable assistance; to Prof. F. C. Newcombe
and to Prof. Ernst Bessey for the loan of sheets, from the herbariums of
the University of Michigan and Michigan Agricultural College; and
especially to Prof. Geo. P. Burns in whose inspiration this bulletin had
its inception and under whose direction the work has progressed to
completion.
CHAS. H. OTIS.
HOW TO STUDY THE TREES
People are everywhere associated with trees. Trees give cooling shade in
our parks and dooryards and along our highways; they lend their beauty
to the landscape and relieve it of monotony; they yield many kinds of
fruits, some of which furnish man and the animals of the forest with
food; and they furnish vast quantities of lumber for a multitude of
uses. How important it is, then, that every person, whether school-child
or grown-up, should become acquainted with our trees. Most people know a
few of our commonest trees, but are ignorant of the great wealth of tree
forms about them. Some who may have wished to go further have been
hindered for lack of a teacher or dismayed by the very multitude of
manuals to which they have had access.
In beginning a study of the trees the student should start on a solid
foundation, eliminating the uncertainties and the errors which no doubt
have appeared and retaining only the established facts. Once started he
should go slowly, assimilating each new discovery before seeking
another. He should begin with the trees nearest home, and, as he
gradually grows to know these in all their aspects, should extend his
trips afield. Not only should he be able to name the trees when they are
fully clothed in their summer dress, but he should as readily know these
same trees when the leaves have fallen and only the bare branches stand
silhouetted against the sky. Then, and only then, will he derive the
utmost satisfaction from his efforts.
The characters which are used in studying the trees are habit, leaves,
flowers, fruit, buds, bark, distribution and habitat. These will be
discussed briefly in the next few pages, the same order that is used in
the detailed descriptions of species being maintained in the present
discussion. A few drawings will also be added to make clear certain
points and to show comparative forms.
NAME.--Every tree has one or several common names and a scientific or
Latin name. Some of these common names are merely local, others have a
more extended use. Some few names apply to totally different species.
Thus, Cottonwood in Michigan is _Populus deltoides_, in Idaho and
Colorado _Populus angustifolia_, in California _Populus fremontii_ and
in Kentucky _Tilia heterophylla_. While it should not be forgotten that
in common speech it is proper as well as convenient to call trees by
their common names, yet, in view of the many uncertainties pertaining to
their use, a scientific name is at times absolutely essential to the
clear understanding of what is meant. Latin is the language in universal
use by all scientists. No longer used by any civilized nation, it has
become a dead language and consequently never changes. Its vocabulary
and its constructions will a thousand years hence be the same as they
are today. Being in universal use among scientists of all nationalities
no confusion arises from the use of a Latin word. The Oak in Germany is
known as _Eiche_, in France as _chêne_ and in Spain as _roble_, but the
Latin word _Quercus_ is the same for all these countries.
A scientific name as applied to trees consists of at least two parts, as
_Quercus alba_; the first named is the genus and is always written with
a capital letter, the second is the species and is written with a small
letter, the two names constituting the briefest possible description of
the particular tree. It is customary to add to these the name or an
abbreviation of the name of the person who first gave the name to the
tree, as _Quercus alba L._, the abbreviation standing for Linnaeus.
Sometimes a third name is used, as _Acer saccharum nigrum_, referring in
this case to a variety of the ordinary Sugar Maple.
Genera which bear a relationship to each other are placed in the same
family, the family name always having the characteristic ending--_aceae_.
Related families are again grouped into orders, with the characteristic
ending--_ales_. Orders are in like manner arranged into larger groups,
called classes, and the latter into still larger groups, divisions,
etc., each with its characteristic ending. Thus, _Acer saccharum nigrum_
(_Michx. f._) _Britt_. is classified as follows:
Division--Spermatophyta
Subdivision--Angiospermae
Class--Dicotyledoneae
Order--Sapindales
Family--Aceraceae
Genus--Acer
Species--saccharum
Variety--nigrum.
HABIT.--Habit, or the general appearance of a plant, is an important
character of identification, especially as we become more and more
familiar with the trees. Two main types are recognized, based on the
manner of branching of the trunk, the upright and the spreading. In the
one the trunk extends straight upwards without dividing, as is typical
in most of the conifers, and in the other the trunk divides to form
several large branches and the broad, spreading crown of most of our
broad-leaf trees. The crown in either case may be regular in outline or
very irregular, straggling or straight-limbed. Moreover, the tree
growing in the open, where there is no crowding and there is plenty of
light, may differ very greatly from the tree in the forest, where the
struggle for existence becomes very keen. A short, thick trunk and low,
spreading, many-branched crown characterizes the tree in the open,
whereas the forest tree has a long, slender, clean trunk and a narrow
crown of few branches. In the descriptions of trees in this bulletin,
unless otherwise stated, the habit in the open is the one given. Again,
the tree may have been injured by storm or insect at some period of its
growth and its natural symmetry destroyed. Moreover, the age of a tree
has a great influence on its outline, young trees being generally narrow
and more or less conical, broadening out as they become older. We may
say, then, that each tree has an individuality of its own, little
eccentricities similar to those that make people different from one
another. And just as we have little difficulty in recognizing our
friends at a distance by some peculiarity of walk or action, so are we
able to recognize a great many trees at a distance by some peculiarity
of form or habit.
[Illustration: I. LEAF OUTLINES
Lanceolate. Ovate. Heart-shaped. Halberd-shaped. Linear. Elliptical.
Oblong. Oval. Orbicular. Oblanceolate. Spatulate. Obovate.]
[Illustration: II. LEAF TIPS
Acuminate. Acute. Obtuse. Emarginate. Mucronate.]
LEAVES.--With the advent of spring the buds of our broad-leaf trees swell
and burst and the leaves come forth and clothe the trees with mantles of
green, hiding the branches which have been bare through the cold winter
months. The evergreens, too, take on new color and begin a new period
of growth. It is the leaves which the beginner finds most interesting
and in which he finds a ready means of identification. It must be
remembered, however, that leaves vary greatly in size and shape and
general appearance. How large are the leaves on a flourishing sprout and
how small on a stunted tree of the same species growing near by, but
under adverse circumstances. How different are the leaves of the big
white oak standing in the yard; they are hardly lobed on the lowermost
branches, while higher up they are deeply cut. Yet, in spite of the many
modifications that leaves undergo, the leaves of any one species have
certain rather constant characters which are found in all forms, and the
student will have little difficulty in selecting and recognizing typical
leaves.
[Illustration: III. LEAF MARGINS
Serrate. Doubly Serrate. Crenate. Undulate. Sinuate. Lobed. Dentate.]
Leaves are either persistent, as in most of our conifers, which stay
green all winter, or they turn various colors with the frost and fall
early in autumn; often they hang dead and lifeless far into the winter.
The points about leaves which we are accustomed to consider are the
position or arrangement of the leaves on the branch, whether simple or
compound, size, shape, texture, color, amount and character of
pubescence, character of the margin, venation, etc. The following
diagrams will serve to illustrate some of the ordinary forms and shapes
of leaves, their margins, etc.
[Illustration: IV. PARTS OF A FLOWER
Perfect Flower. Stamen. Pistil.
a. Sepal (Calyx). b. Petal (Corolla). c. Stamen. d. Pistil. e. Anther.
f. Filament. g. Stigma. h. Style. i. Ovary.]
FLOWERS.--Every tree when old enough bears flowers in its proper season.
Some of these, as the Catalpas, Locusts and Horse-chestnuts are very
showy, others, like the Oaks and Hickories, are comparatively
inconspicuous; some are brilliantly colored, others are of the same
color as the leaves. Nevertheless, the flowers are very accurate means
of classification, and their only drawback is that they last for such a
short period of time each year.
[Illustration: V. TYPES OF INFLORESCENCES
Spike. Raceme. Panicle. Corymb. Umbel. Cyme.]
Just as we have male and female in the animal world, so we have male and
female in the plant world. A few of our trees, as the Locust, Basswood
and Cherries have perfect flowers, bearing both stamens and pistil. The
great majority, however, have unisexual flowers, bearing stamens or
pistils, but not both. When both male and female flowers are found on
the same tree, the flowers are said to be monoecious, and when male
flowers occur on one tree and the female on a different tree, the
flowers are said to be dioecious. The Cottonwood is dioecious, and the
little seeds are surrounded by a tuft of long, white hairs which enables
the wind to carry them to considerable distances from the parent tree,
to the disgust of people living within range. Many cities forbid the
planting of Cottonwood on account of the "cotton." Since in some cases
it is desirable to plant this rapid-growing tree, as in cities burning
large amounts of soft coal, it is a distinct advantage to know that male
trees are lacking in the objectionable "cotton" and may be planted
safely.
Before trees can produce fruit their flowers must be fertilized, i.e.,
pollen from the anther of a stamen must come in contact with the stigma
of a pistil. Some flowers are self-fertilized, others are
cross-fertilized. For a long time it was not known how fertilization was
accomplished, but now we know that many insects, like the nectar-loving
bees and butterflies, and in other cases the wind transport the pollen
from one flower to another, often miles being traversed before the right
kind of flower or a flower in the right stage of development is found.
And many are the modifications of flowers to insure this transference of
pollen.
FRUIT.--So numerous and so varied are the forms of tree fruits that it
would only be confusing to enumerate their various characters. Some
fruits, as the achenes of the Poplars and Willows, are so small and
light that they are carried long distances by the wind; others, like the
hickory nuts and walnuts, are too heavy to be wind-blown. Many fruits
are of considerable economic and commercial importance and are gathered
and marketed on a large scale; such are the hickory nuts, walnuts,
chestnuts, etc. Some, not esteemed by man, form an important article of
diet for the birds and small animals of the forest. Unfortunately, there
are a number of limitations to the usefulness of fruit for
identification purposes. Some trees require years to mature their fruit.
Many trees, while producing an abundance of fruit at certain intervals,
bear none at all or only very small and uncertain quantities between the
years of abundance. Again, in the case of dioecious trees, only the
female or pistillate bear fruit. Notwithstanding these limitations tree
fruits are a very valuable aid to the student, and he should always
search closely for evidences of their presence and character.
[Illustration: VI. WINTER TWIG OF RED MULBERRY
a. Tip-scar. b. Lateral bud. c. Leaf-scar. d. Stipule-scars.]
WINTER-BUDS.--Buds, with their accompanying leaf-and stipule-scars form
the basis of tree identification in winter. The size, color, position
with reference to the twig, number and arrangement and character of
bud-scales, etc., are all characters of the greatest value in winter
determinations. Buds are either terminal or lateral, depending on their
position on the twig. A lateral bud is one situated on the side of a
twig in the axil of a leaf-scar. A terminal bud is one situated at the
end of a twig, where it is ready to continue the growth of the twig the
following spring. In the keys an important consideration is the presence
or absence of the terminal bud. Inasmuch as the determination of this
point gives the beginner some trouble at first, it is hoped that the
accompanying diagrams and explanatory remarks will make the distinction
clear.
[Illustration: VII. WINTER TWIG OF BLACK WALNUT
a. Terminal bud.
b. Lateral bud.
c. Leaf-scar.
d. Bundle-scars.
e. Pith.]
In the Elms, Willows, Basswood and many other species the terminal bud
and a small portion of the tip of the twig dies and drops off in late
autumn, leaving a small scar at the end of the twig (a, fig. VI). The
presence of this tip-scar indicates that the terminal bud is absent.
Often a lateral bud will be found very close to the tip-scar (b, fig.
VI), which, bending into line with the twig, makes it appear terminal.
However, the presence of a leaf-scar immediately below it shows it to be
a lateral bud (c, fig. VI). In some large twigs the eye unaided will
serve to find the tip-scar, but with the smaller twigs a hand-lens is
necessary.
The arrangement, size and shape of the leaf-scars (c, fig. VII) are
important factors in identification by winter characters. Within the
leaf-scars are one or more dots (d, fig. VII), sometimes quite
inconspicuous, often very prominent. These are the scars left by the
fibro-vascular bundles which run through the petiole into the blade of
the leaf, and are designated as bundle-scars. There may be only one as
in Sassafras and Hackberry, two as in Ginkgo, three as in the Poplars
and Cherries, or many; and they may be arranged in a U- or V-shaped line,
or they may be without definite order. Often stipule-scars (d, fig. VI)
occur on either side of the leaf-scar; these are scars left by the fall
of a pair of small leaflets called stipules and located at the base of
the leaves, and their form varies according to the form of the stipules
which made them.
BARK.--The woodsman uses the bark of a tree more than any other character
in distinguishing the trees about him, and he is often able to use this
character alone with much accuracy at great distances. However, the
appearance of bark differs so greatly with the age of the tree and with
its environment that it is difficult to describe it accurately. Some
characters are distinctive, however, and serve as a ready means of
identification; such characters are the peeling of the Sycamore and
Paper Birch, the "shagging" of the Shagbark Hickory, the spicy taste of
Sassafras bark and the mucilaginous inner bark of the Slippery Elm.
WOOD.--It is not expected that the information given under this heading
will be of any particular value in identifying living trees. Often,
however, the student finds himself in the midst of felling operations,
when the information concerning the wood is of considerable value.
DISTRIBUTION AND HABITAT.--To a lesser extent do distribution and habitat
of a species aid in the identification of a tree. It is a distinct aid
to know that the Chestnut is native in south-eastern Michigan only and
that the Mountain Ash does not extend south of Ludington. So too,
knowing the water-loving habit of the Swamp White Oak, we would not
expect to find this same tree flourishing on the top of a hard, dry
hill.
The characters, then, which are used to identify the trees about us are
many. Not all will be available at any one time, not all have been
mentioned in the foregoing pages nor in the manual. It is our opinion,
however, that the student will not be greatly handicapped by this lack
of detail, but rather that he will take great interest and genuine
pleasure in discovering these things for himself.
ARTIFICIAL KEYS, HOW MADE AND USED
An artificial key is a scheme for easily and quickly identifying any
unknown object under consideration. This bulletin being devoted to the
trees of Michigan, the keys to be found herein are intended to make it
possible for any person, even if his botanical training be meager, to
determine what trees grow about any home or farm, city park or woodlot
in the state. With certain modifications and limitations they may prove
useful in other localities as well. Since many people are unfamiliar
with the construction and use of keys for identification, it will be the
purpose of the following paragraphs to briefly outline the principles of
construction and the manner of using the keys to be found here.
The keys are based on the most striking similarities and differences
which the various parts of trees--twigs, buds, leaves, etc.--show, i. e.,
those characters which stand out in bold relief, which catch the eye at
first sight. Two alternatives are presented, either a character _is_ or
_is not_ present; these are the only choices possible. Indeed, further
divisions are unnecessary and only lead to confusion and possible
oversight. The two diametrically opposed characters are said to be
coördinate in rank. In the keys they are preceded by the same letter or
letters (_a_ and _aa_ or _b_ and _bb,_ etc.) and are set at the same
distance from the left margin of the page. Often _a_ and _aa,_ or _b_
and _bb_ are further divisible into other groups; in every case the
characters are opposed (a positive and a negative) and are given
coördinate rank. It is desirable for mechanical reasons to divide the
main divisions of the key more or less evenly, but this is not always
feasible, nor should it be religiously adhered to.
Suppose as a concrete example that it is desired to construct a key to
distinguish five houses in a city block. Three of these are of wood
construction, two are of brick, and of the two wooden houses one is
painted white and one brown. We may classify them as follows:
a. Houses wood.
b. Body paint brown. _Smith's house_
bb. Body paint white.
c. Trimmings green color. _Jones' house_
cc. Trimmings slate color. _Brown's house_
aa. Houses brick.
b. Roof gray slate. _Johnson's house_
bb. Roof red tile. _Public Library_
It is desirable in many cases to add other characters to lessen the
liability of confusion, where the characters chosen are not distinct,
and to show the user that he is on the right track. Thus, in the example
just given, green color and slate color under certain defects of the
eye, a coating of dust or deficiencies of the light might be confused,
under which circumstances we would be justified in adding to the above
statements without the criticism of description being made. Thus:
bb.
c. Trimmings green color; gable roof. _Jones' house_
cc. Trimmings slate color; mansard roof. _Brown's house_
The keys in this bulletin are constructed on the above principles. They
are not in all cases as simple as the illustration just used, but if the
reader has mastered the house illustration he will have little or no
trouble with the larger keys. Suppose that (during a summer stroll) you
come across a large tree with rough, hard bark and thin, lobed leaves
which you do not know. Turning to the _Summer Key to the Genera_ you
find first _a. Leaves simple_, and contrasted with this _aa. Leaves
compound._ Obviously the leaf is simple and the genus sought lies in
that portion of the key preceding _aa_, i.e., under _a._ _b_ and _bb_
under _a_ give you a choice between _Leaves needle-shaped_,
_awl-shaped_, _strap-shaped_ or _scale-like_ and _Leaves broad and
flat_. The leaf being broad and flat you pass to _c_ and _cc_ under
_bb_. Here you have a choice between _Leaves alternate or clustered_ and
_Leaves opposite or whorled_. Inspection shows the arrangement to be
opposite, and you know that the genus sought lies in that portion of the
key between _cc_ and _aa_. Passing to _d_ and _dd_ under _cc_ gives the
choice between _Margin of leaves entire or only slightly undulate_ and
_Margin of leaves serrate to lobed_. The leaf is deeply lobed. It is
then either a _Viburnum_ or an _Acer_, and the fact that the leaf-margin
is lobed and not finely serrate brings the chase down to _Acer_. Before
going further go back over the key and make careful note of the
particular characters which were used to separate this genus from the
other genera and try to fix these in mind. This done, turn to the page
indicated, where you will find a _Summer Key to the Species of Acer_.
You run through this key in the same manner that you did the genus key.
If you have been careful in your search you will finally stop at _Acer
saccharum_. Once more pause and go back over this key and try to fix in
mind the characters which were used to separate the various species,
especially the difference between your tree and _Acer platanoides_,
which it so closely resembles. This done, turn to the page indicated and
compare the characters of your tree with the drawings and descriptions.
If you are satisfied with your diagnosis, well and good. If you find
that you are wrong, go over the keys again and find wherein you were led
astray.
Before you leave the tree take a sample of leaf properly labeled which
you can press between the pages of an old magazine and save for future
reference. Do this with other trees which you may find and when you get
home lay them out side by side so that the labels will not show and
compare them. A few trials of this kind will serve to form a mental
picture of each leaf which you will remember.
A very helpful practice for the beginner is that of making keys based
upon various characters. Practice keys of this kind will bring out the
differences and likenesses of trees as will no other means, and
characters which have hitherto escaped the eye will be prominently
brought forward. Nor should the student take his characters from books,
but rather should he go to the woods and get his knowledge first hand.
It is hardly necessary to state that the key is a valuable crutch while
learning to walk, but once the leg is strong enough to bear the weight
it should be discarded, lest it become a burden. A key has for its main
object the guidance of the student through the preliminary steps leading
to a more intimate knowledge of the trees. When once he knows a tree,
instinctively, because of long acquaintance with it, just as he knows
people, then the need for a key will have ceased.
SUMMER KEY TO THE GENERA[A]
a. Leaves simple.
b. Leaves needle-shaped, awl-shaped, strap-shaped or
scale-like.
c. Leaves in clusters of 2-many.
d. Leaves in clusters of 2-5, sheathed, persistent for several
years. PINUS, p. 4.
dd. Leaves in fascicles of 8-many, on short, lateral
branchlets, deciduous in autumn. LARIX, p. 17.
cc. Leaves solitary, not clustered.
d. Leaves opposite.
e. Twigs flattened; leaves all of one kind, scale-like,
decurrent on the stem; fruit a small, pale brown cone. THUJA,
p. 31.
ee. Twigs essentially terete; leaves of two kinds, either
scale-like, or else awl-shaped, often both kinds on the same
branch, not decurrent on the stem; fruit berry-like, bluish.
JUNIPERUS, p. 33.
dd. Leaves alternate or spirally-whorled.
e. Leaves flattened, soft to the touch.
f. Leaves 1/2-1-1/4 inches long, sessile, aromatic; cones 2-4
inches long; bark of trunk with raised blisters containing
resin. ABIES, p. 27.
ff. Leaves seldom over 1/2 inch long, short-petioled, not
aromatic; cones about 3/4 inch long; bark of trunk without
raised blisters. TSUGA, p. 29.
ee. Leaves 4-sided, harsh to the touch. PICEA, p. 18.
bb. Leaves broad and flat.
c. Leaves alternate or clustered, never opposite nor whorled.
d. Margin of leaves entire or only slightly undulate.
e. Leaves heart-shaped or rounded; fruit a legume. CERCIS, p.
167.
ee. Leaves oval, ovate or obovate; fruit not a legume.
f. Branches armed with stout, straight spines; fruit large,
orange-like. MACLURA, p. 133.
ff. Branches without spines; fruit small, not orange-like.
g. Fruit an acorn. QUERCUS, p. 96.
gg. Fruit a drupe or berry.
h. Twigs spicy-aromatic when bruised; leaves of many shapes on
the same branch. SASSAFRAS, p. 139.
hh. Twigs not spicy-aromatic; leaves not of many shapes on the
same branch.
i. Leaves thick, abruptly pointed, very lustrous above, not
clustered at the ends of the branches. NYSSA, p. 209.
ii. Leaves thin, long-pointed, not lustrous above, clustered
at the ends of the branches. CORNUS, p. 202.
dd. Margin of leaves serrate, toothed or lobed.
e. Margin of leaves serrate to toothed.
f. Branches armed with stiff, sharp thorns. CRATAEGUS, p. 151.
ff. Branches not armed.
g. Base of leaves decidedly oblique.
h. Leaf-blades about as long as they are broad, heart-shaped.
TILIA, p. 201.
hh. Leaf-blades 1-1/2 - 2 times as long as they are broad, oval
to ovate.
i. Leaves thin, coarsely but singly serrate; fruit a globular
drupe, ripe in autumn. CELTIS, p. 131.
ii; Leaves thick, coarsely and doubly serrate; fruit a samara,
ripe in spring. ULMUS, p. 122.
gg. Base of leaves essentially symmetrical.
h. Teeth coarse, 2-5 per inch of margin.
i. Leaves very glabrous both sides; fruit a prickly bur.
j. Leaves 3-5 inches long, very lustrous beneath; bark close,
smooth, steel-gray. FAGUS, p. 93.
jj. Leaves 6-8 inches long, not lustrous beneath; bark
fissured, brownish. CASTANEA, p. 95.
ii. Leaves pubescent or white-tomentose, at least beneath;
fruit not a prickly bur.
j. Leaves 2-4 inches long, broadly ovate to suborbicular;
fruit a very small capsule, falling in spring. POPULUS, p. 44.
jj. Leaves 4-7 inches long, oblong-lanceolate to obovate;
fruit an acorn, falling in autumn. QUERCUS, p. 96.
hh. Teeth fine, 6-many per inch of margin.
i. Leaf-petioles laterally compressed; leaves tremulous.
POPULUS, p. 44.
ii. Leaf-petioles terete; leaves not tremulous.
j. Leaf-blades at least 3 times as long as they are broad.
k. Twigs brittle; fruit a very small capsule, falling in
spring. SALIX, p. 34.
kk. Twigs tough; fruit a fleshy drupe, falling in late summer
or autumn. PRUNUS, p. 152.
jj. Leaf-blades not more than twice as long as they are broad.
k. Leaf-blades about twice as long as they are broad.
l. Margin of leaves singly serrate; fruit fleshy.
m. Lenticels conspicuous; pith whitish or brownish; bark
easily peeled off in papery layers; buds ovoid. PRUNUS, p.
152.
mm. Lenticels inconspicuous; pith greenish; bark not separable
into papery layers; buds narrow-conical. AMELANCHIER, p. 149.
ll. Margin of leaves doubly serrate; fruit not fleshy.
m. Trunk fluted; fruit inclosed within a halberd-shaped
involucre. CARPINUS, p. 83.
mm. Trunk not fluted; fruit not inclosed within a
halberd-shaped involucre.
n. Bark of trunk gray-brown, broken into narrow, flattish
pieces loose at the ends; fruit in hop-like strobiles. OSTRYA,
p. 81.
nn. Bark of trunk white, yellow or dark brown, platy or
cleaving off in papery layers; fruit not in hop-like
strobiles. BETULA, p. 84.
kk. Leaf-blades almost as broad as they are long.
l. Lower side of leaves more or less downy; sap milky; leaves
not crowded on short, spur-like branchlets; fruit berry-like,
black. MORUS, p. 135.
ll. Lower side of leaves glabrous; sap not milky; leaves
crowded on short, spur-like branchlets; fruit a large, green
pome. PYRUS, p. 142.
ee. Margin of leaves distinctly lobed.
f. Fruit an acorn. QUERCUS, p.96.
ff. Fruit not an acorn.
g. Leaves fan-shaped, with many fine veins radiating from the
base of the blade. GINKGO, p. 3.
gg. Leaves not fan-shaped, without many fine veins radiating
from the base of the blade.
h. Leaf-lobes entire.
i. Leaf-petioles 5-6 inches long; leaves lustrous above; twigs
not aromatic when bruised. LIRIODENDRON, p. 137.
ii. Leaf-petioles about 1 inch long; leaves dull above; twigs
spicy-aromatic when bruised. SASSAFRAS, p. 139.
hh. Leaf-lobes sinuate-toothed to serrate.
i. Leaf-lobes coarsely sinuate-toothed. PLATANUS, p. 141.
ii. Leaf-lobes serrate.
j. Branches armed with stiff, sharp thorns; sap not milky.
CRATAEGUS, p. 151.
jj. Branches unarmed; sap milky. MORUS, p. 135.
cc. Leaves opposite or whorled.
d. Margin of leaves entire or only slightly undulate.
e. Leaves 3-5 inches long; spray fine; fruit an ovoid, scarlet
drupe. CORNUS, p. 202.
ee. Leaves 5-12 inches long; spray coarse; fruit a long,
slender-cylindrical capsule. CATALPA, p. 222.
dd. Margin of leaves serrate to lobed.
e. Margin of leaves finely serrate. VIBURNUM, p. 229.
ee. Margin of leaves distinctly lobed. ACER, p. 172.
aa. Leaves compound.
b. Leaves alternate.
c. Leaves simple-pinnate.
d. Branchlets armed with short, sharp prickles. ROBINIA, p.
169.
dd. Branchlets unarmed.
e. Leaflets entire with the exception of 2 or more coarse,
glandular teeth at the base. AILANTHUS, p. 171.
ee. Leaflets serrate the entire length.
f. Upper leaflets less than 1 inch broad.
g. Trunk and large branches armed with stout spines; leaflets
3/4-1-1/2 inches long. GLEDITSIA, p. 165.
gg. Trunk and large branches unarmed; leaflets 2-3 inches
long. PYRUS, p. 142.
ff. Upper leaflets 1-5 inches broad.
g. Leaflets 5-11; pith homogeneous. CARYA, p. 66.
gg. Leaflets 11-23; pith chambered. JUGLANS, p. 60.
cc. Leaves bi-pinnate.
d. Trunk and large branches armed with stout spines; leaflets
3/4 - 1-1/2 inches long, GLEDITSIA, p. 165.
dd. Trunk and large branches unarmed; leaflets 2 - 2-1/2
inches long. GYMNOCLADUS, p. 163.
bb. Leaves opposite.
c. Leaves pinnately compound; fruit a samara.
d. Leaflets 3-5; samaras paired. ACER, p. 172.
dd. Leaflets 7-11, exceptionally 5; samaras not paired.
FRAXINUS, p. 210.
cc. Leaves digitately compound; fruit a prickly bur. AESCULUS,
p. 194.
WINTER KEY TO THE GENERA[B]
a. Leaves persistent and green throughout the winter,
needle-shaped, awl-shaped or scale-like.
b. Leaves in clusters of 2-5, sheathed. PINUS, p. 5.
bb. Leaves solitary, not clustered.
c. Leaves opposite.
d. Twigs flattened; leaves all of one kind, scale-like,
decurrent on the stem; fruit a small, pale brown cone. THUJA,
p. 31.
dd. Twigs essentially terete; leaves of two kinds, either
scale-like, or else awl-shaped, often both kinds on the same
branch, not decurrent on the stem; fruit berry-like, bluish.
JUNIPERUS, p. 33.
cc. Leaves alternate or spirally-whorled.
d. Leaves flattened, soft to the touch.
e. Leaves 1/2 - 1-1/4 inches long, sessile, aromatic; cones
2-4 inches long; bark of trunk with raised blisters containing
resin. ABIES, p. 27.
ee. Leaves seldom over 1/2 inch long, short-petioled, not
aromatic; cones about 3/4 inch long; bark of trunk without
raised blisters. TSUGA, p. 29.
dd. Leaves 4-sided, harsh to the touch. PICEA, p. 19.
aa. Leaves not persistent and green throughout the winter, but
deciduous in early autumn.
b. Twigs, branches or trunks armed with stiff, sharp prickles,
spines or thorns.
c. Thorns or spines not exceeding 1/2 inch in length on the
branches.
d. Spines in pairs at each node; buds rusty-hairy, 3-4
superposed; fruit a flat pod. ROBINIA, p. 169.
dd. Spines one at each node; buds glabrous, not superposed;
fruit orange-like. MACLURA, p. 133.
cc. Thorns or spines much exceeding 1/2 inch in length on the
branches.
d. Thorns usually branched, situated above the nodes; lateral
buds superposed, the lower covered by bark; fruit a flat pod.
GLEDITSIA, p. 165.
dd. Thorns unbranched on twigs, situated at the nodes; lateral
buds not superposed, not covered by bark; fruit a small pome.
CRATAEGUS, p. 151.
bb. Twigs, branches or trunks unarmed.
c. Leaf-scars mainly crowded on short, stout, lateral shoots.
d. Bundle-scar 1; fruit a cone, usually present. LARIX, p. 17.
dd. Bundle-scars 2; fruit a globose drupe falling in autumn.
GINKGO, p. 3.
cc. Leaf-scars distributed along the lateral branches.
d. Leaf-scars (or some of them) 3 at a node, i. e., whorled.
CATALPA, p. 223.
dd. Leaf-scars 1-2 at a node, i.e., not whorled.
e. Leaf-scars 2 at a node, i.e., opposite.
f. Terminal buds 1/2 - 1-1/2 inches long, resin-coated; twigs
very stout. AESCULUS, p. 195.
ff. Terminal buds rarely exceeding 1/2 inch in length, not
resin-coated; twigs not conspicuously stout.
g. Leaf buds with 1 pair of scales visible.
h. Buds scurfy-pubescent. VIBURNUM, p. 229.
hh. Buds glabrous. CORNUS, p. 203.
gg. Leaf buds with 2 or more pairs of scales visible.
h. Bundle-scars usually 3, distinct, separated. ACER, p. 174.
hh. Bundle-scars many, minute, more or less confluent in a
U-shaped line. FRAXINUS, p. 211.
ee. Leaf-scars 1 at a node, i.e., alternate.
f. Bundle-scars 1-3.
g. Bundle-scar only 1, or appearing as 1.
h. Twigs bright green, spicy-aromatic; bundle-scar appearing
as a horizontal line; terminal bud present; pith homogeneous.
SASSAFRAS, p. 139.
hh. Twigs brownish, not spicy-aromatic; bundle-scar appearing
as a large dot; terminal bud absent; pith chambered. CELTIS,
p. 131.
gg. Bundle-scars 3 or in 3 compound, but distinct groups.
h. Terminal bud present.
i. Stipule-scars present.
j. First scale of lateral bud directly in front, i.e., exactly
above the center of the leaf-scar; twigs brittle; pith
somewhat star-shaped in cross-section. POPULUS, p. 45.
jj. First scale of lateral bud not directly in front, i. e.,
to one side of the center of the leaf-scar; twigs not brittle;
pith circular in cross-section. PRUNUS, p. 153.
ii. Stipule-scars absent.
j. Buds bright to dark red, the terminal 1/8 - 1/4 inch long.
k. Branches contorted, bearing many short, spur-like
branchlets; fruit an apple an inch or more in diameter, light
green. PYRUS, p. 143.
kk. Branches not contorted, not bearing short, spur-like
branchlets; fruit berry-like, 1/2 inch long, blue-black.
NYSSA, p. 209.
jj. Buds brownish to gray, the terminal exceeding 1/4 inch in
length.
k. Buds narrow-conical, sharp-pointed; leaf-scars small,
narrowly crescent-shaped; twigs about 1/16 inch thick; pith
homogeneous; fruit berry-like, not present. AMELANCHIER, p.
149.
kk. Buds broadly conical to ovoid, blunt-pointed; leaf-scars
conspicuous, broadly heart-shaped; twigs about 1/4 inch thick;
pith chambered; fruit a nut, often present. JUGLANS, p. 61.
hh. Terminal bud absent (sometimes present on short shoots of
_Betula_).
i. Stipule-scars present.
j. Bud-scale only 1 visible; twigs brittle. SALIX; p. 34.
jj. Bud-scales 2 or more; twigs not brittle.
k. Bark smooth, close, warty or peeling into papery layers,
but not flaky nor rough-ridged.
l. Tip of bud appressed; fruit berry-like. CELTIS, p. 131.
ll. Tip of bud not appressed; fruit not berry-like.
m. Trunk fluted; catkins not present in winter; lenticels not
elongated horizontally; low tree or bushy shrub. CARPINUS, p.
83.
mm. Trunk not fluted; catkins usually present in winter;
lenticels elongated horizontally; large trees. BETULA, p. 85.
kk. Bark flaky or rough-ridged, not warty nor peeling off in
papery layers.
l. Bundle-scars depressed, conspicuous; bark thick, more or
less deeply furrowed. ULMUS, p. 123.
ll. Bundle-scars not depressed, inconspicuous; bark thin,
broken into narrow, flattish strips, loose at the ends.
OSTRYA, p. 81.
ii. Stipule-scars absent.
j. Buds silky-pubescent, depressed; twigs stout, clumsy,
blunt, with conspicuous leaf-scars. GYMNOCLADUS, p. 163.
jj. Buds glabrous, not depressed; twigs slender, with
inconspicuous leaf-scars.
k. Buds 1/8 inch long, obtuse, somewhat flattened and
appressed; pith with reddish longitudinal streaks. CERCIS, p.
167.
kk. Buds 1/8-1/4 inch long, acute, not flattened nor
appressed; pith without reddish streaks. PRUNUS, p. 153.
ff. Bundle-scars 4-many.
g. Bundle-scars in a single U-shaped line.
h. Terminal bud present; fruit berry-like; a shrub or small
tree. PYRUS, p. 143.
hh. Terminal bud absent; fruit not berry-like; large trees.
i. Stipule-scars present; twigs slender.
j. Stipule-scars encircling the twig; leaf-scars nearly
surrounding the bud; bark peeling off in thin plates, exposing
the lighter colored inner bark. PLATANUS, p. 141.
jj. Stipule-scars not encircling the twig; leaf-scars not
nearly surrounding the bud; bark thick, rough-ridged, not
exposing the inner bark. ULMUS, p. 123.
ii. Stipule-scars absent; twigs very stout.
j. Bundle-scars usually not more than 5. GYMNOCLADUS, p. 163.
jj. Bundle-scars usually 6-12. AILANTHUS, p. 171.
gg. Bundle-scars variously grouped or scattered, but not in a
single line.
h. Terminal bud present.
i. Stipule-scars present.
j. Stipule-scars encircling the twig; visible bud-scales 2,
united. LIRIODENDRON, p. 137.
jj. Stipule-scars not encircling the twig; visible bud-scales
more than 2, not united.
k. Buds 4 times as long as broad, not clustered at the tips of
vigorous shoots; fruit a prickly bur. FAGUS, p. 93.
kk. Buds not 4 times as long as broad, usually clustered at
the tips of vigorous shoots; fruit an acorn. QUERCUS, p. 98.
ii. Stipule-scars absent. CARYA, p. 67.
h. Terminal bud absent (occasionally present in _Castanea_).
i. Bud at end of twig very obliquely unsymmetrical,
mucilaginous when chewed. TILIA, p. 201.
ii. Bud at end of twig symmetrical, not mucilaginous when
chewed.
j. Bud-scales 2-3 visible; pith star-shaped in cross-section;
sap not milky; fruit a prickly bur, present; large tree.
CASTANEA, p. 95.
jj. Bud-scales 4-8 visible; pith not star-shaped in
cross-section; sap milky; fruit berry-like, not present; small
tree. MORUS, p. 135.
MANUAL OF TREES
DESCRIPTION OF SPECIES
WITH
SUMMER AND WINTER KEYS
TO THE SPECIES
[Illustration: +Ginkgo. Maidenhair Tree+
1. Winter twig, × 1/2.
2. Leaf, × 1/2.
3. Staminate flowering branchlet, × 1/2.
4. Staminate flower, enlarged.
5. Pistillate flower, enlarged.
6. Fruit, × 1.]
+GINKGOACEAE+
+Ginkgo.[C] Maidenhair Tree+
_Ginkgo biloba L._ [_Salisburia adiantifolia Smith_]
HABIT.--A slender tree in youth, with slender, upright branches, becoming
broader with age and forming a symmetrical, pyramidal crown; probably
60-80 feet high, with a trunk diameter of 2-4 feet.
LEAVES.--Clustered at the ends of short, spur-like shoots, or scattered
alternately on the long terminal branches; simple; 2-5 inches broad;
more or less fan-shaped; usually bilobed and irregularly crenate at the
upper extremity; thin and leathery; glabrous, pale yellow-green on both
sides; petioles long, slender; turning a clear, golden yellow before
falling in autumn.
FLOWERS.--May, with the leaves; dioecious; the staminate in
short-stalked, pendulous catkins, 1 to 1-1/2 inches long, yellow; the
pistillate more or less erect on the shoot, long-stalked, consisting of
2 naked ovules, one of which usually aborts.
FRUIT.--Autumn; a more or less globose drupe, orange-yellow to green,
about 1 inch in diameter, consisting of an acrid, foul-smelling pulp
inclosing a smooth, whitish, somewhat flattened, almond-flavored nut.
WINTER-BUDS.--Terminal bud about 1/8 inch long, conical, smooth, light
chestnut-brown; lateral buds divergent, usually only on rapid-growing
shoots.
BARK.--Twigs gray-brown and smooth; thick, ash-gray and somewhat
roughened on the trunk, becoming more or less fissured in old age.
WOOD.--Light, soft, weak, close-grained, yellow-white to light red-brown,
with thin, lighter colored sapwood.
NOTES.--Origin in dispute, but probably a native of northern China.
Extensively cultivated in China and Japan, where its fruit is esteemed.
Easily propagated from seed. Thrives in deep, well-drained, rich soil.
Practically free from insect and fungous attacks, and little harmed by
the smoke of cities. Probably hardy throughout the southern half of the
Lower Peninsula.
+SUMMER KEY TO THE SPECIES OF PINUS+
a. Leaves 5 in a cluster; cones 4-10 inches long. _P.
strobus_, p. 7.
aa. Leaves 2 in a cluster; cones less than 4 inches long.
b. Leaves 1-3 inches long.
c. Leaves about 1 inch long, divergent; cones sessile,
pointing forward towards the tip of the branch, persistent
10-15 years, opening very unevenly. _P. banksiana_, p. 9.
cc. Leaves 1-1/2-3 inches long, slightly divergent; cones
stout-stalked, pointing away from the tip of the branch,
maturing in second season, opening evenly. _P. sylvestris_, p.
13.
bb. Leaves 3-6 inches long.
c. Bark of trunk red-brown; cones maturing in second season,
about 2 inches long; cone-scales thickened at the apex, but
unarmed. _P. resinosa_, p. 15.
cc. Bark of trunk gray to nearly black; cones maturing in
first season, 2-3 inches long; cone-scales thickened at the
apex and topped with a short spine. _P. laricio austriaca_, p.
11.
+WINTER KEY TO THE SPECIES OF PINUS+
a. Leaves 5 in a cluster; cones 4-10 inches long. _P. strobus_,
p. 7.
aa. Leaves 2 in a cluster; cones less than 4 inches long.
b. Leaves 1-3 inches long.
c. Leaves about 1 inch long, divergent; cones sessile,
pointing forward towards the tip of the branch, persistent
10-15 years, opening very unevenly. _P. banksiana_, p. 9.
cc. Leaves 1-1/2-3 inches long, slightly divergent; cones
stout-stalked, pointing away from the tip of the branch,
maturing in second season, opening evenly. _P. sylvestris_, p.
13.
bb. Leaves 3-6 inches long.
c. Bark of trunk red-brown; cones maturing in second season,
about 2 inches long; cone-scales thickened at the apex, but
unarmed. _P. resinosa_, p. 15.
cc. Bark of trunk gray to nearly black; cones maturing in
first season, 2-3 inches long; cone-scales thickened at the
apex and topped with a short spine. _P. laricio austriaca_, p.
11.
[Illustration: +White Pine+
1. Cluster of leaves, × 1.
2. Cross-sections of leaves, enlarged.
3. Partly opened cone, × 3/4.
4. Cone-scale with seeds, × 1.]
+PINACEAE+
+White Pine+
_Pinus strobus L._
HABIT.--A large tree 60-80 feet high, with a trunk diameter of 2-4 feet;
forming a wide, pyramidal crown. Formerly trees 100-150 feet in height
and 5-7 feet in trunk diameter were not exceptional.