ese 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