f _red_, while in the
weeping willow it is _yellowish green_.

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 Orie