THE NATURAL VEGETATION OF
The United States can be divided into three forest belts, Atlantic, Rocky Mountain and Pacific. The central or Rocky Mountain forest is separated from the other forests by a belt of desert on the west and a belt of grassland on the east.1
B. E. Livingston and F. Shreve have constructed a generalised map of the vegetation of the United States of America,2 which forms a useful basis for a discussion of the distribution of vegetation. A generalised map of this kind is particularly valuable in a study of the influence of vegetation on the history of the exploration of the area, as the great mass of information contained on a detailed map is apt to obscure the main influences. The area under consideration in this book is shown on Fig. 14, and the vegetation regions are numbered. On the east there are three distinct areas of forest, none of which greatly concern this book and can be summarily treated.
REGION I. THE SOUTH-EASTERN EVERGREEN FOREST . This forest region is not very dense and is largely composed of evergreen needle-leaved trees with an admixture of deciduous broad-leaved trees.3____________________