Michigan Trees Part 1

Michigan Trees.

by Charles Herbert Otis.

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 a.s.sociate 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 cla.s.ses 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 ma.n.u.script 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 ill.u.s.tration 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 a.s.sistance 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 a.s.sistance; 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 a.s.sociated 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 quant.i.ties of lumber for a mult.i.tude 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 mult.i.tude 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, a.s.similating 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 _chene_ 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 const.i.tuting 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 relations.h.i.+p 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 cla.s.ses, and the latter into still larger groups, divisions, etc., each with its characteristic ending. Thus, _Acer saccharum nigrum_ (_Michx. f._) _Britt_. is cla.s.sified as follows:

Division--Spermatophyta Subdivision--Angiospermae Cla.s.s--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.

[Ill.u.s.tration: I. LEAF OUTLINES

Lanceolate. Ovate. Heart-shaped. Halberd-shaped. Linear. Elliptical.

Oblong. Oval. Orbicular. Oblanceolate. Spatulate. Obovate.]

[Ill.u.s.tration: II. LEAF TIPS

Ac.u.minate. 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 flouris.h.i.+ng sprout and how small on a stunted tree of the same species growing near by, but under adverse circ.u.mstances. 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.

[Ill.u.s.tration: 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 p.u.b.escence, character of the margin, venation, etc. The following diagrams will serve to ill.u.s.trate some of the ordinary forms and shapes of leaves, their margins, etc.

[Ill.u.s.tration: 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 cla.s.sification, and their only drawback is that they last for such a short period of time each year.

[Ill.u.s.tration: 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, Ba.s.swood and Cherries have perfect flowers, bearing both stamens and pistil. The great majority, however, have unis.e.xual 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 b.u.t.terflies, 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 quant.i.ties 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.