Pool: THE VEGETATION OF THE SANDHILLS OF NEBRASKA 259 



Composition of the Grama-Buffalo-Grass Association 



Botiteloua oligostachya 



Aragallus lambertP- 

 Aristida longiseta 

 Bouteloua curtipendula 



Allium nuttallii 

 Argemone intermedia 

 Aristida oligantha 

 Artemisia canadensis 

 Artemisia frigida 

 Astragalus mollissimus 

 Cactus viviparus 

 C rot on texensis 

 Cucurbita foetidissima 

 Eriogonum multiceps 

 Grindelia squarrosa 

 Gutierrezia sarothrae 



dominant species 



Bulbilis dactyloides 

 principal species 



Festuca octoiiord^ 



Plantago purshii^ 



Psoralea argophylla 



secondary species 



Hedeonia hispida 

 Lacinaria punctata 

 Malvastrum coccineum^ 

 Monarda citriodord^ 

 Munroa squarrosa 

 Opuntia fragilis 

 Opuntia polycantha 

 Psoralea tenuiHora 

 Schedonnardus paniculatus 

 Sideranthus spinulosus 

 Talinum teretifolium 



1 Forming patches or communities. 



The most striking variation produced in the general monoto- 

 nous, often more or less parched, background of grama-buflfalo- 

 grass association is produced by the presence of patches wherein 

 some of the secondary species are dominant and completely over- 

 shadow the short-grasses. Sometimes these areas are of consider- 

 able size and frequency so that the short-grasses lose to a certain de- 

 gree their overpowering influence. In the sandier situations, for 

 instance, the Aristidas, or Stipa, or even Andropogon scoparius may 

 become so numerous as to change completely the nature of the vege- 

 tative cover, yielding a type of vegetation that would be difficult to 

 classify or relate to any of the better-defined associations. 



During the latter part of May or early June many of the more 

 open, somewhat sandy areas of this association, especially as it is 

 found in certain dry valleys to the westward and along the Middle 

 Loup River, are covered by dense communities of Festuca octoHora. 

 When the plants of this short-lived species first appear they are of a 

 bright green color so that the areas thus dominated appear as promi- 



