CHARACTERISTICS OF THE PLAINS AREA. 
277 
The Great Plains, extending from the North Saskatchewan to the 
Mexican boundary, are mainly covered with the various bunch grasses. 
The luxuriance of the growth differs greatly in different localities, being 
modified by the general and local climate. In general terms the growth 
is more luxuriant in the north than in the south, and in the eastern por- 
tion than towards the west, although at and near the base of the Eocky 
Mountains and Black Hills the growth is again quite luxuriant, owing 
to the increased moisture of climate produced by the proximity to the 
mountains. 
Here and there, in the more arid localities, which will be defined in 
some detail farther on, are areas wholly or in part given over to sage, 
cactus, or the Spanish bayonet (Yucca angnstifolia). 
Passing beyond the wall of the Eocky Mountains one enters still 
more arid regions where the grasses give way still more to Artemisia, 
and other members of the arid flora, which, in the great interior basin, 
between the Eocky Mountains and the Sierra Nevada and Cascade 
Eange, form the primary growths of such of the country as is not utterly 
sterile. 
Everywhere, however, on the mountain slopes the country is better 
watered than in the valleys, and where not covered by timber the 
grasses are more luxuriant than below. 
The bottom lands of rivers, too, are, for a greater or less breadth, in a 
measure artificially irrigated, and the grasses are more close, approach- 
ing a turf, and often grow much higher. Such areas, however, are com- 
paratively insignificant in extent. Many of these bottom lands, too, 
are covered with willow and cottonwood trees, to the partial or total 
exclusion of grasses. In the region of the plains and the great interior 
valleys, these strips of timber along the streams are practically the oidy 
timber. 
Greasewood takes the place of Artemisia in many localities, seeming 
to prefer a heavy alkaline clay soil, while sage grows indifferently on a 
clayey or sandy soil, but on the latter it grows most freely and luxu- 
riantly. 
"Burnable" land (and by this term we mean land susceptible of being 
burned over cheaply and economically) is practically \' identical with graz- 
ing land. Bunch and grama grasses burn with the greatest freedom, the 
only difficulty being to control the fire and prevent it from doing dam- 
age. Most sage-land has more or less grass among the sage. Indeed, 
grass land grades into sage barrens by insensible degrees and as the 
latter are burnable only with difficulty, the line of division between burn- 
able and non-burnable land must in this case be mainly an arbitrary 
one, drawn according to the judgment of the observer. 
A heavy luxuriant growth of sage will burn freely, as travelers in the 
West have had frequent opportunity of observing, but a low, stunted 
growth of this plant, which covers great areas of thin, poor soil, can 
be coaxed into burning only by constant attention, and it would there- 
. fore be very expensive to burn over great areas. 
