The Plants of Michigan.

by Henry Allan Gleason.

PREFACE

This book is not intended for the expert botanist. He should consult one of the regular Manuals which give full descriptions of each species of plant.

Neither is it intended for the merely curious. Only those who have sufficient interest in a plant to observe it can find its name by this book.

Furthermore, it is not a textbook. It does not attempt to convey botanical information, but offers merely an opportunity to learn the names of plants.

Its mission is fully accomplished if, through its use, students, vacationists, and plant-lovers in general are able to recognize by name the plants about them.

HOW TO USE THE BOOK

One recognizes a plant by the presence of structural features peculiar to itself, and not found on any other kind of plant. In such a book as this, these characters are given one or a few at a time, and contrasted with the characters which other sorts of plants possess. Such a presentation is called a Key, and by its proper use the name may be learned of any plant considered in it. This process is called Identification.

Keys are constructed in several different ways, although the principle of all is the same. In this book, the user will begin with lines 1a and 1b on the page headed Key to the Groups. Each of these lines includes some descriptive matter, but only one of them can apply to the plant being identified. For example, if the plant to be identified is an Oak, line 1a will apply perfectly, and the same line will also apply to any other kind of tree or to any shrub. But if the plant is a Violet, a b.u.t.tercup, or any other herb, line 1b agrees and line 1a will not apply.

At the end of each line is a reference to be consulted next. If the plant is a tree or shrub, one turns accordingly to Group 1, on page ix, and begins again at the first number given. If the plant is an herb, he follows the reference to line 2, just below, and again compares the plants with lines 2a and 2b.

Under every number at least two lines of description are given, designated a and b, and under a few numbers additional lines appear, designated c, d, etc. In every case, the user of the key will select from the different lines under the same number that particular line which agrees with the structure of the plant, and follow up the reference given at the end of that line. Eventually one finds at the end of a line, instead of a number, the name of a family of plants, to which this particular plant belongs, and then turns over to the page where this family is treated. Under each family is a similar key, to be followed in exactly the same way, until finally one finds instead of a number the common name and the scientific name of the plant in hand. The process of identification is now completed, and the student has found the name of the plant.

In some cases, a reference is made in the key to a particular portion of the family key. One then turns directly to this particular number in the family key, and continues his identification in the usual way.

As a definite example of the use of the key, suppose that one has in hand a branch of the White Oak, and that he does not know its name. To determine its name, he will trace it through the following steps in the key. Under the Key to the Groups, it agrees with line 1a, which refers to Group 1, Woody Plants. Under this group it agrees in structure with line 1a, which refers to 2; with line 2b, referring to 21; with line 21b, referring to 22; with 22b, referring to 29; with 29b, referring to 32; with 32c, referring to 47; with 47b, referring to 48; with 48b, referring to 51; with 51b, referring to number 1b in the Beech Family.

Turning to the proper number in this family, the plant is referred to line 3; it agrees with line 3c, referring to 10; with 10a, referring to 11; and with 11b, which gives the name of the plant. White Oak, _Quercus alba_.

As a second example, suppose one has a common yellow-flowered plant blooming on lawns and roadsides in spring. Under the Key to the Groups, it agrees with 1b, referring to 2; with 2b, referring to 3; and its net-veined leaves place it in 3b, referring to Group 4, Dicotyledones.

Under this group, its basal leaves place it in 1b, referring to 2; its simple leaves in 2b, referring to 18; the absence of stem-leaves places it in 18b, referring to 23; its solitary flowers on each flower-stalk place it in 23b, referring to 24; its yellow flowers agree with 24a, referring to 25; and its milky juice refers the plant to number 16, in the Composite Family. In the key to this family, its lobed leaves agree with 16b, referring on to 17; its large flowers with 17b, giving one the common name Dandelion, and referring on to 18 to determine which kind of Dandelion the plant may be.

At some point in the key there will be found for each plant a statement in parentheses. This is general information concerning the height of the plant, the color of the flowers, or the season of bloom. It must be remembered that the height of plants is subject to great variation; that most plants have white-flowered varieties; and that the month of bloom depends largely on the lat.i.tude and the climate. Therefore this general information should not be used as means of distinguishing species.

=The names of plants.= Each plant bears a scientific name. This is composed of two parts and is usually of Latin or Greek derivation. In some cases these names are taken directly from the Latin language, as _Quercus_, the Oak, or _Acer_, the Maple. In other cases the name may indicate some characteristic feature of the plant, as _Polygonum_, many joints, for the Knotweed, or _Ammophila_, sand-loving, for the Beach Gra.s.s.

An English name is also given for almost every kind of plant. In a few cases there is no accepted English name, and none has been given. In many cases the same English name applies to several kinds of plants and has been repeated for each. When this is so, the common name is given in the key in parentheses before the scientific name is reached. Thus, if one is satisfied to know merely that his plant is a dandelion, he learns it in line 17b of the key to the Composite Family, but to discover which kind of a dandelion he has, he must follow through the key and use the scientific name.

There is in this book, therefore, no necessity of learning or using scientific names. The less critical may be satisfied with an English name, and others may use the scientific names as they see fit.

=Possible Errors.= In using this book, care must be taken to compare all the lines under each number with the plant, and to use judgment in selecting the right one. While faulty observation or poor judgment may lead to error, a mistake is usually due to carelessness in not following correctly the reference at the end of the line chosen. If one reaches a number in which none of the lines of description agrees with the plant, it is very probable that he has made a mistake at an earlier stage of the identification, and he should then begin anew.

It has been the intention of the author to make the key as nearly as possible proof against errors of judgment. For example, the Indian Turnip may be sought under either Group 3 or Group 4; the Matrimony Vine may be identified either as a shrub or as an herb, and numerous other similar examples may be discovered.

=Botanical Information Needed.= It is presumed that those using the book will be familiar with the parts of the flower and with the commoner descriptive terms applied to leaves. Unusual terms have been avoided as far as possible, but those which do occur, as well as the simpler ones, are explained in the glossary.

In general, only those characters have been used in the keys which can be observed without a magnifying gla.s.s and without dissection of the flower.

In several groups of plants, reference is made to the fuller descriptions to be found in the Manuals. The standard manuals for Michigan are Gray's New Manual of Botany, 7th edition (American Book Company, $2.50), and Britton and Brown, Ill.u.s.trated Flora of the Northern States and Canada (Chas. Scribner's Sons, $13.50). These books may be consulted in most school or public libraries.

All dimensions are expressed in the metric system. For convenience, it may be stated that 25 millimeters (mm.) are about equal to one inch; 1 centimeter (cm.) to two-fifths of an inch; 1 decimeter (dm.) to 4 inches; and 1 meter (m.) is a little more than 3 feet.

KEY TO GROUPS

1a. Trees, shrubs, or woody climbers, with stems which last from year to year Group 1, =WOODY PLANTS=, p. ix.

1b. Herbaceous plants, with stems which live above ground only a single season --2.

2a. Plants with unusual habits or structures, including leafless, colorless, submerged, floating, parasitic, or hollow-leaved plants Group 2, =UNUSUAL PLANTS=, p. xxiii.

2b. Ordinary terrestrial or swamp plants, without unusual structural peculiarities --3.

3a. Leaves parallel-veined (or net-veined in a few species); parts of the flower usually in threes or sixes, never in fives; wood-fibers scattered through the stem; seed with one cotyledon. All plants with definitely parallel-veined leaves may be identified through this division, unless the parts of the flower are distinctly in fives.

Group 3, =MONOCOTYLEDONES=, p. xxvii.

3b. Leaves net-veined (or parallel-veined in a few species); parts of the flower usually in fours or fives; wood-fibers arranged in a circle in the stem; seeds with two cotyledons. All plants with definitely net-veined leaves may be identified through this division. Group 4, =DICOTYLEDONES=, p. x.x.x.

Note:--In order to avoid possible chances of error, many plants have been treated under both of the above groups. The following hints may also be useful in distinguishing Groups 3 and 4:

All herbaceous plants with deeply lobed, dissected or compound leaves may be sought under the Dicotyledones.

All herbaceous plants with five stamens in each flower, or with seven or more stamens and one ovary in each flower, may be sought under Dicotyledones.

GROUP 1, WOODY PLANTS

1a. Trees, with erect stem and central trunk, attaining a height of 6 m.

(20 ft.) or more --2.

1b. Shrubs or woody vines, without true tree habit, or attaining heights of less than 6 m. (20 ft.) --52.

2a. Key for use in earliest spring, for trees which have flowers but no leaves --3.

2b. Key for use with trees bearing leaves --21.

3a. Flowers in catkins, without brightly colored or petal-like parts --4.