part of section 9 and the southwest quarter of section 
4, T. 33 N., R. 2 E., where the stream flows through 
a canyon, the walls of which are St. Peter sandstone. 
The stream cascades over falls into a canyon, 
fig. 11, and then slowly meanders between sandstone 
cliffs. Marshy areas border the stream in many places 
Fig. 11.— Upper part of the canyon at Clark Run. The 
stream enters the canyon by this route, Mallard ducks were 
swimming on the water of the pool below the falls on Octo- 
ber 11, 1962, the date this picture was taken. 
where the canyon cliffs have been eroded away. In 
these areas the skunk cabbage and marsh marigold 
flower in early spring. The latter occasionally blooms 
also in autumn. Bordering the stream are stands of 
blue beech, willows, and other small trees. Mayapple 
forms sizable clones on the relatively dry parts of the 
floodplain. Canada yew, arbor vitae, red cedar, and 
white pine grow on the cliffs. In those places where 
the sandstone cliffs have eroded to leave steep 
slopes, rattlesnake plantain, partridge berry, bunch- 
berry, white pine (some of the trees 24 inches in di- 
ameter), and other plants can be observed. Witch 
hazel, saxifrage, pasture gooseberry, and false lily- 
of-the-valley thrive in the ravines. 
Above the cliffs the conditions are more xeric, 
that is, the water supply is lower and the evaporation 
tate higher. Black oak and Hill’s oak find a favorable 
environment in such sites. Some of the shrubs of the 
xeric bluff-tops are fragrant sumac, smooth sumac, and 
lead plant. Herbaceous plants include little bluestem, 
needle grass, wild indigo, and the narrow-leaved aster. 
Clark Run, similar in many respects to some of 
the canyons of Starved Rock State Park, has not been 
overrun by people. Much of the canyon area and most 
of the adjacent uplands have been pastured, some 
parts severely. In spite of this treatment, some of the 
rare plants have survived. If cattle were removed, 
doubtless Clark Run would revert to a very beautiful 
and biologically rich area. 
Clark Run is presently in private ownership. 
7. ILLINOIS RIVER SAND PRAIRIES 
Along the east side of the [llinois River from the 
big bend in Putnam County south into Scott County 
sizable deposits of sand form terraces upon which a 
dunic topography has developed. These deposits were 
laid down during the Wisconsinan glaciation. At that 
time the meltwater from the ice front with its load of 
sand and silt was flooding the valley of the Illinois 
and aggrading it. After the close of glaciation, the 
river cut its channel into these sand deposits, leav- 
ing the terraces. The sand terraces of the Illinois 
River valley supported forest, prairie, and marshland 
until the coming of European man. After his arrival, 
much of the area of sand terraces was put into culti- 
vation -- into fields of corn, wheat, soybeans, rye, 
melons, or into pine plantations or turkey farms. Scat- 
tered throughout the area are small remnants of forest 
and prairie. 
The University of Illinois owns land on the sand 
terrace northwest of Kilbourne, Mason County. This 
acreage includes both prairie and forest. The prairie 
lacks large dunes but possesses sizable blowouts of 
a compound nature. These blowouts tend to be stabil- 
ized by goat’s rue, fig. 12, three species of three-awn 
grass, the common panic grass of sand areas, Panicum 
pseudopubescens, and the sedge Bulbostylis capil- 
laris. Other sedges, Cyperus schweinitzii and C. fili- 
culmis, grow scattered in the blowouts. Black-jack 
oak thrives at the border of one blowout. 
Elsewhere the sand prairie contains such grasses 
as little bluestem, switchgrass, sand love grass, 
needle grass, and the tall Calamovilfa longifolia var. 
magna. In the interstices are such plants as goat’s 
rue, polygala, small to moderately large patches of 
prickly pear, and rose mallow. A common shrub of this 
prairie is fragrant sumac. In one depression where the 
sand remains quite moist, blackberries and seed-box 
thrive. 
It is impossible to find all the plants of the Illi- 
nois River sand prairies growing in this one locality 
near Kilbourne. Within a 15-mile radius, in other 
prairie remnants, numerous other species can be 
found, including two plants rare in Illinois, Cristatella 
jamesii and bladder-pod. 
During the early part of this century a number of 
workers were occupied with studies of sand areas in 
Illinois. The work of Hart & Gleason (1907) is con- 
sidered a biological classic. A study of the sand land 
vegetation by Gleason (1910) included the [Illinois 
River sand areas. Vestal (1913) studied the relation- 
ships of plants and animals, especially the insects, 
11 
