Comparisons:  The English elm (Ulmus campestris) is also a tall,
    dignified tree commonly seen under cultivation in America, but may
    be told from the American species by the difference in their general
    contour.  The branches of the English species spread out but do not
    arch like those of the American elm, and the bark of the English elm
    is darker and coarser, Fig. 38.  Little tufts of dead twigs along the
    main branches and trunk of the tree are characteristic of the
    English elm and will frequently help to distinguish it from the
    American elm.

    The Camperdown elm may be recognized readily by its dwarf size and
    its low drooping umbrella-shaped crown.

LOMBARDY OR ITALIAN POPLAR (Populus nigra, var. italica)

Distinguishing characters:  Its tall, slender, spire-like form and
    rigidly erect branches, which commence low on the trunk, make this
    tree very distinct at all seasons of the year.  See Fig. 39.

Leaf:  Triangular in shape, similar to that of the Carolina poplar but
    smaller, see Fig. 40.

Range:  Asia, Europe, and North America.

Soil and location:  The poplar is easily grown in poor soil, in any
    location, and is very hardy.

Value for planting:  The tree has a distinctive form which makes it
    valuable for special landscape effects.  It is also used for shelter
    belts and screening.  Like all poplars it is short lived and will
    stand pruning well.

Commercial value:  None.

[Illustration:  FIG. 41.—­Carolina Poplar.]

Comparisons:  The Carolina poplar, or Cottonwood (Populus deltoides)
    can be told from the Lombardy poplar by its wider crown and its more
    open branching, Fig. 41.  It may be recognized by its big terminal
    twigs, which are light yellow in color and coarser than those of the
    Lombardy poplar, Fig. 42.  Its bark is smooth, light and
    yellowish-green in young trees, and dark gray and fissured in older
    specimens.  Its large, conical, glossy, chestnut-brown bud is also
    characteristic, Fig. 42.  Its flowers, in the form of large catkins,
    a peculiarity of all poplars, appear in the early spring.  The
    Carolina poplar is commonly planted in cities because it grows
    rapidly and is able to withstand the smoke and drouth conditions of
    the city.  Where other trees, however, can be substituted with
    success, the poplar should be avoided.  Its very fast growth is
    really a point against the tree, because it grows so fast that it
    becomes too tall for surrounding property, and its wood being
    extremely soft and brittle, the tree frequently breaks in
    windstorms.  In many cases it is entirely uprooted, because it is not
    a deep-rooted tree.  Its