But the far western conifers are remarkable, not only for their variety, but still more for the density of their growth, already mentioned, and for their great size, Fig. 52. The pines, spruces and hemlocks of the Puget Sound region make eastern trees look small, and both the red fir and the redwood often grow to be over 250 feet high, and yield 100,000 feet, B.M., to the acre as against 10,000 feet, B.M., of good spruce in Maine. The redwood, Fig. 53, occupies a belt some twenty miles wide along the coast from southern Oregon to a point not far north of San Francisco and grows even taller than the famous big trees. The big trees are the largest known trees in diameter, occasionally reaching in that measurement 35 feet. [Illustration: Fig. 52. Virgin Forest of Red Fir, Red Cedar, Western Hemlock, and Oregon Maple. Ashford, Washington. _U. S. Forest Service._] [Illustration: Fig. 53. Redwood Forest. Santa Cruz Co., Calif. _U. S. Forest Service._] The big tree, Fig. 54, occurs exclusively in groves, which, however, are not pure, but are scattered among a much larger number of trees of other kinds. [Illustration: Fig. 54. Big Tree Forest. Sierra National Forest, California. _U. S. Forest Service._] The great and unsurpassed Puget Sound forest is destined to be before long the center of the lumber trade of this country. These two great forests of the east and the west both run northward into British America, and are there united in a broad belt of subarctic forest which extends across the continent. At the far north it is characterized by the white spruce and aspen. The forest is open, stunted, and of no economic value. Taking all the genera and species together, there is a far greater variety in the eastern than in the western forests. A considerable number of genera, perhaps a third of the total, grow within both regions, but the species having continental range are few. They are the following: Larch (_Larix laricina_), white spruce (_Picea canadensis_), dwarf juniper (_Juniperus communis_), black willow (_Salix nigra_), almond leaf willow (_Salix amygdaloides_), long leaf willow (_Salix fluviatilis_), aspen (_Populus tremuloides_), balm of Gilead (_Populus balsamifera_), and hackberry (_Celtis occidentalis_). [Footnote 1: ORIGINAL FOREST REGIONS OF THE UNITED STATES. Area Area Thousand acres Per cent. Northern forest 158,938 8.4 Hardwood forest 328,183 17.3 Southern forest 249,669 13.1 Rocky Mountains forest 155,014 8.1 Pacific forest 121,356 6.4 Treeless area 887,787 46.7 --------- ----- Total land area 1,900,947 100.0 ] THE DISTRIBUTION AND COMPOSITION OF NORTH AMERICAN FORESTS. REFERENCES:[A]