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 latitude 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
Grass.

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 dan