[Illustration:  FIG. 33.—­Twig of Norway Maple.]

Comparisons:  The red maple is apt to be confused with the silver maple,
    but the latter can be distinguished by its turned-up twigs and scaly
    bark over the whole trunk of the tree, which presents a sharp
    contrast to the straight twig and smooth bark of the red maple.  The
    latter has a bark similar to the beech, but its branches are
    opposite, while those of the beech are alternate.

NORWAY MAPLE (Acer platanoides)

Distinguishing characters:  The bud, Fig. 33, is oval and reddish-brown
    in color; when taken off, a milky juice exudes.  The bark is close. 
    Fig. 34

[Illustration:  FIG. 34.—­Bark of Norway Maple.]

Leaf:  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.