History in its broadest aspect is a record of man's migrations from one environment to another.

Except on their southern borders the great northern forests are not good as a permanent home for man.

No part of the world can be truly understood without a knowledge of its garment of vegetation, for this determines not only the nature of the animal inhabitants but also the occupations of the majority of human beings.

Man could not stay there forever. He was bound to spread to new regions, partly because of his innate migratory tendency and partly because of Nature's stern urgency.

America forms the longest and straightest bone in the earth's skeleton.

For the source of any characteristic so widespread and uniform as this adaptation to environment we must go back to the very beginning of the human race.

In America the most widespread type of forest is the evergreen coniferous woodland of the north.