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.]