Fern Fiora or NEBRASKA—I 9 
central portion. The western boundary is quite dis- 
tinct, although there are outlying sandhills in the foot- 
hill region. The area is about 18,000 square miles, a 
little more than one-fourth of the area of the state. 
The soil is porous and sandy. The hills are broken, 
abrupt or rounded, frequently pitted with blowouts 
or crater-like depressions, and the valleys are deep 
and narrow. The variable contours of the hills and 
blowouts are the direct result of the prevailing winds. 
Drainage systems are poorly established. Large ponds 
and small lakes occur throughout the region and lakes 
of considerable size occur near the heads of the water 
courses, particularly in Cherry, Grant and Hooker 
counties. Lost creeks are numerous. These streams, 
rising in ponds or springs, flow on the surface for a 
distance and then sink in the soil to pursue a sub- 
terranean course, occasionally coming to the surface 
for a short distance only to be lost again. The valleys 
along streams are broad and marshy, their limits marked 
by high sandhills. Buttes occur occasionally in the 
western part. This is the bunch-grass region of the 
state. Woodland vegetation is scanty. 
In favorable situations, usually in moist soil, there 
occur: Dryopteris cristata (rarely), Dryopteris spinulosa 
(rarely), Dryopteris thelypteris (often locally abundant), 
Onoclea sensibilis, Woodsia oregana (rarely), Marsilea 
vestita, Azolla caroliniana (rarely). Equisetum arvense 
(in ey soil), Hquisetum laevigatum, Equisetum variegatum 
(rarely), and Selaginella rupestris (locally) which forms 
mats on hillsides. 
Tue PLATEAU OR FoorHitt REGION 
The plateau region, in the western part of the state, 
comes rather abruptly from the sandhill region. It is 
an elevated district well marked by numerous isolated 
buttes and by deep and precipitous ravines. It is the 
short-grass region of Nebraska. 
