The distinguishing mark of spruce trees is the woody or horny projection on which the leaf is set. Look at the twigs of a tree which you think may be a fir or a spruce. Wherever the leaves have fallen, the spruce twig is rough ened by these spirally arranged leaf-brackets. Leaf-scars on a fir twig are level with the bark, leaving the twig smooth. Spruce twigs are always roughened, as described above.
Most spruce trees have distinctly four-angled leaves, sharp-pointed and distributed spirally around the shoot, not two-ranked like fir leaves. They are all pyramidal
trees with flowers and fruits of the coniferous type. The cones are always pendent and there is an annual crop. The wood is soft, not conspicuously resinous, straight-grained and valuable as lumber.
The genus picea comprises eighteen species, seven of which belong to American forests. These include some of the most beautiful of coniferous trees.