368 Intinois NaturAL History Survey BULLETIN 
grassy knobs were prairies on steep slopes, 
or hill prairies. It is surprising that no 
earlier descriptions of hill prairies are ex- 
tant. Certainly the French settlers saw 
the grassy slopes and perhaps named the 
village of Prairie du Rocher (Prairie of 
the Rock) after the prairie above the cliffs. 
The capable botanist, André Michaux, 
who traveled from Kaskaskia to Cahokia 
and visited the village of Prairie du 
Rocher in 1795, apparently made no rec- 
ord, in that part of his journal included 
by Sargent (1889), of grasslands on the 
bluffs. Early gazetteers, as those of Peck 
(1834) and Ellsworth (1837), contain 
references to wet, dry, level, and undulat- 
ing prairies, but apparently nothing about 
prairies on the bluffs. Short (1845) 
wrote a good description of the autumnal 
aspect of flatland prairies; his journey did 
not take him far enough to the west to 
include hill prairies. 
Some references to hill prairies of IIli- 
nois have appeared in the past 50 years. 
Hus (1908) described the bluffs in the 
vicinity of Collinsville and mentioned open 
hillsides with grasses dominant and blue- 
grass the chief species. Vestal (1918) 
cited numerous prairie inclusions near 
Charleston, described their topography, 
and stated essential conditions for their 
presence. Woodard (1924) mentioned 
prairies on bluff-ridges. Vestal (1931) 
reported the occurrence of prairies on 
loess bluffs of the Mississippi River, and 
Vestal & Bartholomew (1941) briefly 
described some prairies on the loess bluffs 
of the Illinois River. 
These authors were concerned only 
with local occurrences of hill prairies in 
Illinois. They did not report on the ex- 
tent of hill prairies in the state, nor did 
they report in detail on the flora of the 
hill prairies, the characteristic plants, 
relative abundance, presence and _ space 
relations as determinable in plot studies, 
or the origin and history of hill prairies. 
In order to obtain the necessary infor- 
mation for a study of these characteristics 
of hill prairies and for a description of 
hill prairie vegetation in Illinois, the 
writer made numerous plant collections 
and plant identifications from 61 hill prai- 
ries, fig. 1, having a combined area of more 
than 200 acres. Detailed data pertaining to 
Vol. 26, Art. 5 | 
the vegetation were obtained from two — 
prairies by use of plot studies, as explained 
in a later section of this paper. 
The locations of some hill prairies were — 
determined by the writer from the field | 
notes made by Dr. Vestal during his trav-_ 
els in the state; of others, as the prairie 
southeast of Menominee Station in Jo — 
Daviess County, from a study of aerial © 
photographs. The majority, however, — 
were found by field reconnaissance of the 
writer. During late autumn and early © 
spring, hill prairies can easily be seen 
from the roads near or at the bases of the 
bluffs. Such roads, called bluff roads on 
some maps, are common in both the Mis- — 
sissippi and Illinois river valleys. In the 
Mississippi River valley, bluff roads were 
traveled by the author from Olive Branch 
in Alexander County northward to a 
point north and west of Glen Carbon in 
Madison County and from Hamburg in 
Calhoun County the 275-mile distance to 
the northwest corner of the state, except 
for short gaps in Hancock, Henderson, 
Mercer, Rock Island, and Jo Daviess 
counties. In the lower Illinois River val- 
ley, bluff roads were traveled from Graf- 
ton to Hennepin, except for a few gaps 
in Mason and Tazewell counties. The lo- 
cations of prairie sites were marked on 
maps of sufficient scale to be used easily. 
Not all hill prairies seen were visited, 
nor were bluffs of small streams exam- 
ined for occurrences of hill prairies. 
Doubtless small prairie openings occur on 
the bluffs of small streams in the western — 
part of the state. In eastern I]linois, Ves- 
tal (1918) observed several prairie open- 
ings along the Embarrass River near 
Charleston. 
ACKNOWLEDGMENTS 
It is indeed a pleasure to acknowledge 
the assistance given by Dr. A. G. Vestal, © 
Department of Botany, University of IIli- 
nois, in the preparation of this study. I 
wish to thank him for his willingness to 
direct this investigation and for the many 
helpful suggestions he made during its 
progress. 
Dr. L. R. Tehon, now deceased, and 
Dr. H. B. Mills, of the Natural History 
Survey, greatly facilitated the progress of 
