results from the tall cliffs and the numerous, adjacent 
rock blocks that strew the slopes from the cliffs to 
the creeks. The cliffs and blocks are sandstone. Be- 
low the sandstone, in some places, layers of coal and 
shale are exposed. The sandstone is subjected to 
erosion by water and, in those places where streams 
of water flow at the cliff bases or cascade over the 
cliffs, huge undercuts, locally called caves, have 
been formed by the breaking away of large masses of 
rock, fig. 36. The small creeks in Jackson Hollow 
3 
Fig. 37.-- Rock selaginella growing in a mass of li- 
chens. This species grows on sandstone in southern Illinois 
and also in sand prairie in central and northern Illinois. 
1. het 7 
oa 
S , 
flow across beds or fragments of sandstone, or beds 
of gravel or of sand, and, near Little Bay Creek, 
through deposits of silt. 
The vegetation of Jackson Hollow falls into two 
main types, grassland and forest. Grassland is re- 
stricted to small prairie openings, most of them above 
the cliffs, or to fields of broomsedge that developed 
on abandoned land. Forests are represented by the 
mesic type, with beech, hard maple, and tulip tree, 
and by the xeric type, with certain oaks and hickories. 
The former type occupies the spaces below the cliffs, 
the latter the dry, stony slopes above the cliffs. 
Smooth alder, river birch, blue beech, and willows 
thrive along the streams, especially on the banks of 
Little Bay Creek at the mouth of Jackson Hollow. 
Farkleberry is a common shrub on the stony slopes 
above the cliffs. The sandstone ledges support nu- 
merous lichens, some grasses, and innumerable 
patches of the moss Grimmia, which when wet are 
deep green but when dry are almost black. 
Many unusual plants occur in Jackson Hollow. 
The orchid Tipularia discolor was collected here 
(Mohlenbrock & Voigt 1959). The first collection of 
filmy fern in Illinois was made in this locality by Dr. 
Mary M. Steagall of Southern Illinois University, 
August 2, 1923. The fern was reported to grow in two 
of the numerous undercuts in the sandstone cliffs 
(Evers 1961). On April 8, 1963, Dr. Warren H. Wagner, 
Jr., professor of botany, University of Michigan, ac- 
companied me to Jackson Hollow and he discovered 
a third stand in a cleft in one of the cliffs. On May 
13, 1963, I found a fourth stand in an undercut. This 
brings to 11 the number of stands of this fern in IIli- 
nois. The clubmoss Lycopodium lucidulum grows on a 
flat sandstone surface in one moist ravine and rattle- 
snake plantain grows nearby. Professor Wagner and | 
found another clubmoss, L. porophilum, on one of the 
sandstone cliff faces. A number of orchids, including 
puttyroot, grow scattered throughout. Indian pipe and 
beech-drops are not rare here. Above the cliffs, rock 
selaginella, fig. 37, and talinum thrive in scattered 
patches. 
Presently Jackson Hollow is owned by the feder- 
al government and is under the control of the United 
States Forest Service. 
22. BELL SMITH SPRINGS 
Several miles east of Jackson Hollow is another 
of the numerous beauty spots of southern [Illinois -- 
Bell Smith Springs Recreational Area. It lies south- 
east of the community known as McCormick, in Pope 
County. Within the area, Spring Branch, Hunting 
Branch, and Hill Branch enter Bay Creek, which then 
Fig. 38.-- A gorge cut into the sandstone along Hill 
Branch at Bell Smith Springs, Pope County. The steep upper 
slopes are in many places covered with mosses and lichens. 
he) 
