314 IOWA ACADEMY OF SCIENCE Vol. XXVI, 1919 



a little less than two-fifths of the area of the state. The soil is 

 porous and sandy. The hills are broken, abrupt or rounded, many of 

 them are pitted with blow-outs or crater-like depressions, and the 

 valleys are deep and narrow. The variable contours of the hills and 

 blow-outs 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 Hook- 

 er counties. Lost creeks are numerous. These are streams which 

 rise in ponds or springs and flow on the surface for a distance and 

 then sink in the soil to pursue a. subterranean course, in some in- 

 stances coming to the surface for a short distance only to be lost 

 again. The valleys are broad and marshy and their limits are 

 marked by high sandhills. A few buttes occur 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 : Dry- 

 optcris crisfata (rarely), Dryoptcris spiiiitlosa (rarely), Dryopteris 

 thelyptcris (locally abundant), Onoclca scnsihilis, Woodsia oregana 

 (rarely), Marsilca vcstita, Azolla caroliniana (rarely), Equisetum 

 arvcnse (in dry soil), Eqiiisctiun lacvigatum, Equisetum z'ariegatmn 

 (rarely), and SelagincUa rupcsiris (locally) which forms mats on 

 sandhills. 



THE PLATEAU OR FOOTHILL 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. 



The fern flora of this region is scanty. The following specie? 

 have been collected : Cheilanthcs feci, in canons ; IVoodsia oregana. 

 on buttes ; Marsilca vestita in ponds ; and SelagincUa rupestris, on 

 exposed dry situations, often forming dense mats on high hills 

 and buttes. 



PINE RIDGE REGION 



Pine Ridge is a northerly facing escarpment extending from 

 Wyoming into Nebraska near the northwest corner and in the 

 middle western part of Sioux county and extending eastward across 

 Sioux, Dawes, Sheridan, and Clierry counties, approximately 

 parallel with the northern boundary of ihe state. The ridge varies 

 from a mile to several miles in width and has its greatest develop- 



