98 AMERICAN FERN JOURNAL 
In the region under consideration, Winneshiek and 
Allamakee Counties are bounded on the north by Minne- 
sota; and Allamakee, Clayton, and Dubuque Counties 
lie along the west bank of the Mississippi River. Most 
of the region lies in what is known as the driftless area, 
that is, an area of rounded hills with no drift mantle 
or debris, while all the surrounding region is heavily 
drift covered. 
Geologically this region, generally speaking, is of the 
oldest in the State. The Saint Croix sandstone of the 
Cambrian era, the Oneota limestone, the Saint Peter 
sandstone, the Trenton limestone, the Galena limestone 
and the Maquoketa shales are successively exposed 
_ from the state line southward. 
A locality with so varied a topography readily gives 
many favorite habitats for ferns. Almost every fern 
native of Iowa may be found and many of them are 
quite frequent in occurrence. 
OPHIOGLOSSACEAE 
BOTRYCHIUM VIRGINIANUM (L.) Swartz. Rich woods; 
frequent; Winneshiek, Allamakee, Clayton, and Du- 
buque Counties. 
OSMUNDACEAE 
OSMUNDA CLAYTONIANA L. Rich woods; common; 
Winneshiek, Allamakee, Clayton, and Dubuque Coun- 
ties. 
POLYPODIACEAE 
ONOCLEA SENSIBILIS L. In rich moist soil; frequent; 
Winneshiek, Allamakee, Clayton, and Dubuque Coun- 
ties. This species is very abundant on the high islands 
in the Mississippi River, east of Waukon Junction, 
Iowa; there is also a small colony in a springy slough 
near Postville, Iowa. 
ONOCLEA sTRUTHIOPTERIS (L.) Hoffm. (Matteuccia 
struthiopteris (L.) Todaro.) My specimen was collected 
