FERN FLORA OF NEBRASKA 315 



ment in Nebraska in Sioux and Dawes counties. Eastward it l)e- 

 comes lower and narrower. The ridge is much broken by deeply 

 cut canons crossing transversely to the general trend. Along this 

 ridge upon the canon sides is a development of the western yellow 

 pine (Pim<s pondcrosa scopulorum). The vegetation peculiar to 

 Pine Ridge extends farther eastward across Brown, Rock, and Keya 

 Paha counties. Pine Ridge is essentially a variation of the wooded 

 blufTs region. 



In favorable, usually moist situations are found: Botrychium 

 virginianum, Afliyriuiu fiUx-foemina (rarely), Cystoptcris fragilis, 

 Dryoptcris spinulosa, Dryoptcris thclyptcris, IVoodsia orcgana, and 

 Equisetmn laevigatum. 



BAD LANDS REGION 



The bad lands in Nebraska are confined largely to Sioux and 

 Dawes counties, in the northwestern part of the state, with oc- 

 casional outliers in the foothill region south of the North Platte 

 river in ScottsblutT county. The region is a rugged, submontane 

 one, marked with deep canons, mostly drained by Hat creek and 

 White river and their tributaries. The larger part of the region is 

 known as the Hat creek basin. The soil is largely clays and marls, 

 absorbs little water, and readily erodes. This unstable soil receives 

 little rain and much summer heat, hence there is little or no vege- 

 tation. 



In favorable situations in the canons are found: Botrychiiiin 

 virginiaiinm, Filix fragilis, IVoodsia orcgana, Eqidsetuin arvcnsc, 

 Equisetmn laevigatum, and Equisctuui robitstuni. 



GENERAL DISTRIBUTION 

 The fern flora in Nebraska is represented by seventeen genera 

 and twenty-six species. Of these Botrychium neglcctum, Osmunda 

 rcgalis, Osmunda claytoniana, Cryptogramma acrostichoides, Dry- 

 optcris cristata, Notholccna dcalhata, and Isoctcs mclanopoda arc- 

 quite rare, each being known from but one locality in the state. 

 Cheilanthcs feci, Dryoptcris spinulosa, and Aqolla carotin iana are 

 each known from two localities. Fcllaca atropurpurca and Athy- 

 rium filix-foemina have been collected in three or four localities. 

 Adiantum pcdatum, a common eastern fern but which ranges across 

 the continent, occurs in Nebraska only in the southeastern quarter. 

 Botrychium virginianum, Filix fragilis, Dryoptcris thclyptcris, 

 Onoclca scnsibilis, Marsilia vcstita, Equisctum arvcnsc, Equisctum 

 laevigatum, and Equisctum robustum are the only species that are 



