The Forest Types in Detail
The Boreal or Spruce Type.—The northernmost type of forest, which covers almost the whole of eastern North America from the arctic tundra down to latitude 45°, with many more or less isolated areas farther south, especially in the mountains, is mainly composed of jack pine (Pinus Banksiana), tamarack (Larix laricina), two or three species of spruce (Picea), balsam fir (Abies balsamea), and arbor-vitæ
Dense Growth of Spruce {Picea Mariana) and Arbor-vitæ (Thuja) in a Cold Swamp, Cheboygan Co., Michigan. August, 1912.
or northern white cedar (Thuja occidentalis). In places some one of these may cover considerable areas exclusively (this is especially true of the pine), but usually two or three of them are mixed together. They have much in common in general appearance, mature trees being as a rule spindle-shaped or narrowly conical in outline, with more or less deflexed branches, and leaves an inch or less in length. The tamarack is deciduous, and the rest evergreen.
Forests of similar aspect, and made up mostly of trees of the same genera, cover large areas in all the cooler parts of the northern hemisphere. Doubtless on account of the abundance of such trees in northern Europe, where most of our Anglo-Saxon traditions originated, the spindle-shaped tree has become firmly established as the conventional type of conifer. Illustrations of these trees in their native haunts abound in publications dealing with outdoor life in the extreme north-
