FerN Fiora or NEBRASKA—I v 
willows. The river is broad and shallow with frequent 
sandbars. 
The Big Blue river with its tributaries drains much of 
the southeastern portion of the state. The current is 
slow, the bed and banks muddy, the valleys broad, level, 
rich and frequently heavily wooded. 
The fern species that may be found in the river valleys 
are Osmunda regalis (rarely), Dryopteris thelypteris, and 
Onoclea sensibilis. The fern allies are Equisetum robus- 
tum and Equisetum fluviatile. 
Woopep Buurrs REGION 
This region consists of narrow strips of country border- 
ing on the river valleys on one side and the uplands on 
the other. The line of demarcation with the river valley 
is rather sharp although the woods are frequently con- 
tinuous. The separation of the wooded bluffs from the 
uplands is often not sharply drawn, there being varying 
degrees of divergence, yet within limits it is distinctive. 
The wooded bluffs extend in narrow dichotomous strips 
over much of the state paralleling the valleys of the 
main water courses. They reach their greatest develop- 
ment near the Missouri river which is the center of their 
extension westward. Upland woods are an extension 
from the wooded bluffs into favorable situations. The 
trees are of the broad leaf species except in the north- 
west where there is a development of the yellow pine. 
In Nebraska the fern flora reaches its greatest develop- 
ment in this region. The principal fern species of this 
region are Botrychium virginianum, Adiantum pedatum, 
and Filix fragilis. In the crevices of the rock cliffs, 
often more or less exposed, are found Cryptogramma 
acrostichoides (rarely), Notholaena dealbata (rarely and 
locally), Pellea atropurpurea, Woodsia obtusa, and on dry 
rocky soil Selaginella rupesiris (rarely). 
