FEDERAL AND STATE RESERVATIONS 227 
cies of hardwoods, especially in the swamps and along 
the river courses. 
The second great district includes the St. Law- 
rence Basin, Southern Canada, and the Appalachian 
system of mountains and extends westward to the 
Prairies. In this district many deciduous species and 
conifers grow well. 
The third great district is the Prairies, where 
trees do not grow naturally, except here and there 
and along streams, but where, with care, they can 
be induced to grow, and when once established con- 
tinue to thrive. 
West of the Prairies are the Arid Plains and 
Basins, practically desert, where trees do not grow 
without irrigation except in high mountainous dis- 
tricts of the Rockies where there is sufficient mois- 
ture. 
The next district is the Pacific Coast Region, 
where, owing to an abundance of moisture and 
warmth, there is a very luxuriant growth even as far 
north as Alaska. 
The next district is the Sub-Arctic Forest, which 
extends across Canada to Labrador. It consists 
mostly of conifers of slow growth and of little value. 
Then away southward in Central America, Mex- 
ico, and the West Indies there is the Great Tropical 
District in which frost, never occurs except on high 
