[Illustration:  FIG. 51.—­Bark of the Black or Sweet Birch.]

Commercial value:  The wood of the sycamore is coarse-grained and hard to
    work; used occasionally for inside finishing in buildings.

Other names:  Buttonball, buttonwood.

Comparisons:  The Oriental sycamore (Platanus orientalis) an
    introduced species, is apt to be confused with the Occidental
    sycamore, but may be told from the latter by the number of seed
    balls suspended from the tree.  In the case of the Oriental species,
    the seed balls hang in pairs or (rarely) three or four together. 
    In the Occidental, the seed balls are generally solitary and very
    rarely in pairs.

GRAY OR WHITE BIRCH (Betula populifolia)

Distinguishing characters:  The dull-white color of the bark on the
    trunk and the dark triangular patches below the insertion of the
    branches distinguish this tree; see Fig. 50.  The bark of the young
    trunks and branches is reddish-brown in color and glossy.  The bark
    adheres closely to the trunk of the tree and does not peel in loose,
    shaggy strips, as in the case of the yellow or golden birch.  It is
    marked by small raised horizontal lines which are the lenticels or
    breathing pores.  These lenticels are characteristic of all birch and
    cherry trees.  In addition to the distinction in the color of the
    bark, an important character which distinguishes the gray birch from
    all other species of birch, is found in the terminal twigs, which
    are rough to the touch.

Form and size:  A small tree.  Frequently grows in clumps.

Range:  Eastern United States.

Soil and location:  The gray birch does best in a deep, rich soil, but
    will also grow in poor soils.

Enemies:  The bronze-birch borer, a wood-destroying insect, and
    Polyporus betulinus, a fungus, are its chief enemies.

Value for planting:  Its graceful habit and attractive bark gives the
    tree an important place in ornamental planting.  It may be used to
    advantage with evergreens, and produces a charming effect when
    planted by itself in clumps.

[Illustration:  FIG. 52.—­Bark of the Beech.]

[Illustration:  FIG. 53.—­Buds of the Beech Tree.]

Commercial value:  The wood is soft and not durable.  It is used in the
    manufacture of small articles and for wood pulp.

Other characters:  The fruit is a catkin.

Comparisons:  The paper birch (Betula papyrifera) is apt to be
    confused with the gray birch, because both have a white bark.  The
    bark of the paper birch, however, is a clear white and peels off in
    thin papery layers instead of being close.  It very seldom shows any
    dark triangular markings on the trunk.  Its terminal twigs are not
    rough and its trunk is usually straighter and freer from branches.