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 Buttercup, 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.