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 can be told at a glance by its general branching habit. The limbs arch out into a wide-spreading *fan or vase-like crown* which loses itself in numerous fine drooping branchlets. See Fig. 37. [Illustration: FIG. 37.--American Elm.] Leaf: The leaves are simple, alternate, and from 2 to 5 inches long. [Illustration: FIG. 38.--English Elm in Winter.] Form and size: It is a tall tree with a trunk that divides a short distance above ground. Its general contour, together with the numerous branches that interlace its massive crown, give the elm an interesting and stately appearance which is unequaled by any other tree. [Illustration: FIG. 39.--Lombardy Poplar.] Range: Eastern North America. Soil and location: The elm prefers a deep, rich and moist soil, but will adapt itself even to the poor soil of the city street.