Pool : THE VEGETATION OF THE SANDHILLS OF NEBRASKA 253 



Sheridan and Box Butte counties. Pound and Clements report that 

 this species is also abundant on "the dry, flat, sandy stretches in 

 McPherson County." Many of the gaily-colored legumes such as 

 Aragallus lamberti and Lupinns plattensis, as well as Pentstemon 

 albidus and P. acuminatus, are frequent and abundant members of 

 this association as it is seen toward the western limits of the sand- 

 hills. 



As we go eastward many of the distinctive secondary species 

 drop out and bunch-grass interstitials come in with greater fre- 

 quency. The Stipa hills of Holt County for instance do not exhibit 

 any such kaleidoscopic changes so noticeable farther west during 

 the spring and early summer because of so many brightly colored 

 species in the high plains type of this association. 



THE WIRE-GRASS TRANSITION ASSOCIATION 



The wire-grass transition association as here delimited is some- 

 what Hke the "Beard-Grass Formation" of Pound and Clements and 

 also similar to the "wire-grass association" of the "Short-grass 

 Formation" of Shantz. The association is clearly intermediate 

 between the typical prairie-grass formation and the typical short- 

 grass formation, but within our limits its relationship is more clearly 

 shown with the former. Farther westward the relation is undoubt- 

 edly more strongly with the short-grass formation as has been 

 shown by Shantz (60) in his studies of Great Plains vegetation. 



Composition of the Wire-Grass Transition Association 

 dominant species 

 Aristida hasiramea Aristida purpurea 



Aristida longiseta Sporoholus cuspidatus 



principal species 

 Bouteloua curtipendula Psoralea argophylla 



Bouteloua hirsuta Psoralea tenuiUora 



Bouteloua oligostachya Stipa comata 



Bulbilis dactyioides Stipa spartea 



Cactus viviparus 



SECONDARY SPECIES 



Allionia linearis Carduus undulatus 



Andropogon scoparius Chrysopsis villosa 



Aristida oligantha Eatonia obtusata 



