f: Like the leaf of the sugar maple but thicker in texture and darker
in color. Fig. 35.

Form and size: A tall tree with a broad, round head.

Range: Europe and the United States.

Soil and location: Will grow in poor soil.

Enemies: Very few.

Value for planting: One of the best shade trees.

Commercial value: None.

Other characters: The _bark_ is close like that of the mockernut
hickory.

Comparisons: The Norway maple is apt to be confused with the _sycamore
maple_ (_Acer pseudoplatanus_), but differs from the latter in
having a reddish bud instead of a green bud, and a close bark
instead of a scaly bark.

BOX ELDER (_Acer negundo_)

Distinguishing characters: The terminal *twigs are green*, and the buds
are round and small. Fig. 36.

Leaf: Has three to seven leaflets.

[Illustration: FIG. 35.--Leaf of Norway Maple.]

Form and size: A medium-sized tree with a short trunk and wide-spreading
top.

Range: Eastern United States to the Rocky Mountains.

Soil and location: Grows rapidly in deep, moist soil and river valleys,
but accommodates itself to the dry and poor soil conditions of the
city.

[Illustration: Figure 36.--Twig of the Box Elder.]

Enemies: Few.

Value for planting: Used as a shade tree in the Middle West, but the
tree is so ill formed and so short-lived that it is not to be
recommended.

Commercial value: None. The wood is soft.

Other characters: The _bark_ of the trunk is smooth and yellowish-green
in young trees and grayish brown in older specimens. The _flowers_
appear in the early part of April. The _fruit_ takes the form of
yellowish-green keys which hang on the tree till late fall.

Other common names: The box elder is also commonly known as the
_ash-leaf maple_.

GROUP VI. TREES TOLD BY THEIR FORM: ELM, POPLAR, GINGKO AND WILLOW

How to tell them from other trees: The trees described in this group are
so distinctive in their general _form_ that they may, for the
purpose of study, be grouped together, and distinguished from all
other trees by this characteristic.

How to tell them from each other: The American elm is _vase-like_ in
shape; the Lombardy poplar is narrow and _spire-like_; the gingko,
or maidenhair tree, is _odd_ in its mode of _branching_; and the
weeping willow is extremely _pendulous_.

AMERICAN ELM (_Ulmus americana_)

Distinguishing characters: The tree