August, 1955 
Evers: Hitt Prarrtes oF ILLINOIS 
401 
Fig. 16.—Part of the west-facing slope of Swarnes hill prairie at Hamburg, Calhoun 
County. Echinacea, Melilotus, and Psoralea were common on this slope. 
of the monument divided the prairie al- 
most equally into pastured and unpas- 
tured areas. The pastured segment occu- 
pied a west-facing slope, fig. 16, the un- 
pastured a west- and_ southwest-facing 
slope. The unpastured surface that bor- 
dered the rock ledge was stony, level near 
the ledge, and gradually steepening up- 
ward from the ledge. Bouteloua curti- 
pendula was there locally dominant. In- 
terspaces contained many individuals of 
Houstonia nigricans. The unpastured 
prairie of the steeper slopes and the top 
of the loess-capped bluff were dominated 
by Andropogon scoparius. Scattered 
clumps of Bouteloua curtipendula and A. 
gerardi were present, and Asclepias steno- 
phylla occurred occasionally in the inter- 
spaces. The pastured slope supported a 
prairie that was dominated by d.. sco- 
parius. Near the top of the bluff, as well 
as at the top, Rhus glabra was locally 
dominant. Psoralea tenuiflora was com- 
mon in the pastured prairie area. Swarnes 
prairie was visited September 7, 1949; 
April 14, May 27, July 1, and August 12, 
1950; and September 27, 1951. 
Along Rock, Sangamon, and Illinois 
Rivers 
Devil’s Backbone.—The bluff-ridge 
that extends along the Rock River in the 
northeast quarter of section 16, T. 23 N., 
R. 10 E., south of Oregon, Ogle County, 
is given the name Devil’s Backbone on 
the Dixon quadrangle of the United 
States Geological Survey topographic map. 
St. Peter sandstone underlies this ridge. 
When the ridge was last seen, one south- 
east- and two northeast-facing prairie 
openings occupied the upper stony and 
sandy slopes. Sandstone fragments were 
abundant on the northeast-facing slope. 
The openings on this slope were covered 
with prairie in which Poa pratensis was 
very abundant, Andropogon  scoparius 
less abundant, and Bouteloua curtipen- 
dula scattered throughout. Synthyris bul- 
lii also grew there. The southeast-facing 
opening was a sand prairie on a slope. 
A. scoparius was there the dominant grass. 
Selaginella rupestris, together with mosses 
and Androsace occidentalis, grew in the 
interspaces. Devil’s Backbone was visited 
