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. [Illustration: 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. [Illustration: FIG. 10.--Twig of the Hemlock.] GROUP III. THE RED CEDAR AND ARBOR-VITAE