Studies of Trees. Jacob Joshua Levison
under side, while those of the hemlock, Fig. 10, are flat and are marked by two white lines on the under side.
The Norway Spruce (Picea excelsa)
Distinguishing characters: The characteristic appearance of the full-grown tree is due to the drooping branchlets carried on main branches which bend upward (Fig. 7).
Leaf: The leaves are dark green in color and are arranged spirally, thus making the twigs coarser to the touch than the twigs of the hemlock or fir. In cross-section, the individual leaflet is quadrilateral, while that of the pine is triangular.
Form and size: A large tree with a straight, undivided trunk and a well-shaped, conical crown (Fig. 7).
Range: Northern Europe, Asia, northern North America.
Soil and location: Grows in cool, moist situations.
Enemies: The foliage of the spruce is sometimes affected by red spider, but is apt to be more seriously injured by drought, wind, and late frosts.
Value for planting: Commonly planted as an ornamental tree and for hedges. It does well for this purpose in a cool northern climate, but in the vicinity of New York City and further south it does not do as well, losing its lower branches at an early age, and becoming generally scraggly in appearance.
Fig. 8.—A Group of Hemlock.
Commercial value: The wood is light and soft and is used for construction timber, paper pulp, and fuel.
Other characters: The fruit is a large slender cone, four to seven inches long.
Comparisons: The white spruce (Picea canadensis) may be told from the Norway spruce by the whitish color on the under side of its leaves and the unpleasant, pungent odor emitted from the needles when bruised. The cones of the white spruce, about two inches long, are shorter than these of the Norway spruce, but are longer than those of the black spruce.
It is essentially a northern tree growing in all sorts of locations along the streams and on rocky mountain slopes as far north as the Arctic Sea and Alaska. It often appears as an ornamental tree as far south as New York and Pennsylvania.
The black spruce (Picea mariana) may be told from the other spruces by its small cone, which is usually only about one inch in length. In New England it seldom grows to as large a size as the other spruce trees.
It covers large areas in various parts of northern North America and grows to its largest size in Manitoba. The black spruce has little value as an ornamental tree.
The Colorado blue spruce (Picea parryana or Picea pungens) which is commonly used as an ornamental tree on lawns and in parks, can be told from the other spruces by its pale-blue or sage-green color and its sharp-pointed, coarse-feeling twigs. Its small size and sharp-pointed conical form are also characteristic.
It grows to a large size in Colorado and the Middle West. In the Eastern States and in northern Europe where it is planted as an ornamental tree, it is usually much smaller.
Fig. 9.—Twig of the Norway Spruce.
Hemlock (Tsuga canadensis)
Distinguishing characters: Its leaves are arranged in flat layers, giving a flat, horizontal and graceful appearance to the whole branch (Fig. 8). The individual leaves are dark green above, lighter colored below, and are marked by two white lines on the under side (Fig. 10).
The leaves are arranged on little stalks, a characteristic that does not appear in the other evergreen trees.
Form and size: A large tree with a broad-based pyramidal head, and a trunk conspicuously tapering toward the apex. The branches extend almost to the ground.
Range: The hemlock is a northern tree, growing in Canada and the United States.
Soil and location: Grows on all sorts of soils, in the deepest woods as well as on high mountain slopes.
Enemies: None of importance.
Value for planting: The hemlock makes an excellent hedge because it retains its lowest branches and will stand shearing. In this respect it is preferable to the spruce. It makes a fair tree for the lawn and is especially desirable for underplanting in woodlands, where the shade from the surrounding trees is heavy. In this respect it is like the beech.
Commercial value: The wood is soft, brittle, and coarse-grained, and is therefore used mainly for coarse lumber. Its bark is so rich in tannin that it forms one of the chief commercial products of the tree.
Other characters: The fruit is a small cone about ¾ of an inch long, which generally hangs on the tree all winter.
Fig. 10.—Twig of the Hemlock.
Group III. The Red Cedar and Arbor-Vitae
How to tell them from other trees: The red cedar (juniper) and arbor-vitae may be told from other trees by their leaves, which remain on the tree and keep green throughout the entire year. These leaves differ from those of the other evergreens in being much shorter and of a distinctive shape as shown in Figs. 12 and 13. The trees themselves are much smaller than the other evergreens enumerated in this book. Altogether, there are thirty-five species of juniper recognized and four of arbor-vitae. The junipers are widely distributed over the northern hemisphere, from the Arctic region down to Mexico in the New World, and in northern Africa, China, and Japan in the Old World. The arbor-vitae is found in northeastern and northwestern America, China, and Japan. The species mentioned here are those commonly found in America.
How to tell them from each other: The twigs of the arbor-vitae are flat and fan-like as in Fig. 13; the twigs of the red cedar are needle-shaped or scale-like as in Fig. 12. The foliage of the arbor-vitae is of a lighter color than that of the red cedar, which is sombre green. The arbor-vitae will generally be found growing in moist locations, while the red cedar will grow in dry places as well. The arbor-vitae generally retains its lower branches in open places, while the branches of the red cedar start at some distance from the ground.
Red Cedar (Juniperus virginiana)
Fig. 11.—The Red Cedar.
Distinguishing characters: The tree can best be told at a glance by its general form, size and leaves. It is a medium-sized tree with a symmetrical, cone-like form, Fig.