GROUP VII.  TREES TOLD BY THEIR BARK OR TRUNK:  SYCAMORE, BIRCH, BEECH, BLUE BEECH, IRONWOOD, AND HACKBERRY

How to tell them from other trees:  The color of the bark or the form of
    the trunk of each of the trees in this group is distinct from that
    of any other tree.

How to tell them from each other:  In the sycamore, the bark is
    mottled; in the white birch, it is dull white; in the beech, it
    is smooth and gray; in the hackberry, it is covered with numerous
    corky warts; in the blue beech, the trunk of the tree is fluted,
    as in Fig. 54, and in the ironwood, the bark peels in thin
    perpendicular strips.

[Illustration:  FIG. 48.—­Bark of the Sycamore Tree.]

THE SYCAMORE OR PLANE TREE (Platanus occidentalis)

Distinguishing characters:  The peculiar mottled appearance of the
    bark (Fig. 48) in the trunk and large branches is the striking
    character here.  The bark produces this effect by shedding in large,
    thin, brittle plates.  The newly exposed bark is of a yellowish green
    color which often turns nearly white later on. Round seed balls,
    about an inch in diameter, may be seen hanging on the tree all
    winter.  In this species, the seed balls are usually solitary, while
    in the Oriental sycamore, a European tree similar to the native one,
    they appear in clusters of two, or occasionally of three or four. 
    See Fig. 49.

[Illustration:  FIG. 49.—­Seed-balls of the Oriental Sycamore.  Note one Seed-ball cut in half.]

[Illustration:  FIG. 50.—­Gray or White Birch Trees.]

Leaf:  The stem of the leaf completely covers the bud.  This is a
    characteristic peculiar to sycamores.

Form and size:  A large tree with massive trunk and branches and a broad
    head.

Range:  Eastern and southern United States.

Soil and location:  Prefers a deep rich soil, but will adapt itself even
    to the poor soil of the city street.

Enemies:  The sycamore is frequently attacked by a fungus (Gloeosporium
    nervisequum), which curls up the young leaves and kills the tips of
    the branches.  Late frosts also often injure its young twigs.  The
    Oriental sycamore, which is the European species, is more hardy in
    these respects than the native one and is therefore often chosen as
    a substitute.

Value for planting:  The Occidental sycamore is now planted very little,
    but the Oriental sycamore is used quite extensively in its place,
    especially as a shade tree.  The Oriental sycamore is superior to the
    native species in many ways.  It is more shapely, faster growing, and
    hardier than the native one.  Both sycamores will bear transplanting
    and pruning well.