I24 UNIVERSITY OF COLORADO STUDIES 
collected by him and recorded in the Flora of Colorado* are known 
from Colorado only by these collections. 
‘“‘The Glade.’?—This is a long north and south valley lying between 
sandstone ridges varying in height at different points. In width the 
valley is from one-eighth to one-quarter of a mile. The soil is fine- 
grained sand with very little lime—well suited to the growth of grasses 
and sagebrush, but not to trees and shrubs. At the lower end of the 
“Glade” near Bellevue the ridges are quite low at the sides of the 
narrow valley, but farther north they are much higher, rising a hundred 
or two hundred feet above the valley. The vegetation of the “Glade” 
is that of the lateral valleys generally and is described later under the 
heading “Valley Grassland Formation.” 
Plant Formations.—The following plant formations may be distin- 
guished in the area under consideration: 
Cercocarpus Scrub Formation.—This is characteristic of the sedimentary rock ridges. 
Usually a rather close scrub but more open in places where the soil contains lime salts. 
Valley Grassland Formation.—Found in the valleys which lie between parallel ridges. 
There is a mixture of grasses and mountain sage with other herbaceous plants. 
Upland Dry Grass Formation.—Small xerophytic grass patches on areas of close- 
grained soil scattered along the rock ridges. 
Canyon Forest Formation.—Mixed forest of deciduous and coniferous trees occupying 
narrow canyons and stream-banks. 
Foothill Sagebrush-Grass Formation.—A xerophytic grassland formation with low- 
growing species of sagebrush (Artemzsia) and various perennial flowering herbs. 
Foothill Forest Formation.—An open forest on the granite foothills dominated by Pinus 
scopulorum. 
Meadow Formation.—Characteristic of poorly drained humus soil along streams, and 
of low, moist places in the lateral valleys even where there is no running water. 
Cercocarpus Scrub Formation.—In naming this formation by its 
shrub constituent (Cercocarpus parvifolius) rather than from the trees. 
(Pinus scopulorum and Sabina scopulorum) it is well to state that the 
shrubs form really the all-important feature. The trees are so few that 
they make little impression to the eye while the shrubs, especially at the 
line where they meet the Valley Grassland Formation, are very con- 
spicuous. At this place there is often a distinct line where the shrubs 
stop, with no stragglers at all extending to the fine-grained soil below. 
t RYDBERG, Flora of Colorado, Bull. 100 Colo. Agr. Coll. Exp. Sta. 1906. 
