252 MINNESOTA BOTANICAL STUDIES 



Composition of the Spear-Grass Association 



DOMINANT species 



Stipa comata Koderia cristata 



principal or secondary species 

 Ahronia fragrans Erysimum asperimum 



Allionia linearis Lacinaria punctata 



Amorpha canescens Lupinus plattensis 



Andropogon hallii Malvastrum coccineum 



Andropogon scoparius Monarda citriodora 



Anogra coronopifolia Pentstemon albidus 



Aragallus lamberti Plantago piirshii 



Aristida purpurea Psoralea argophylla 



Aster canescens Psoralea digitata 



Astragalus adsurgens Psoralea esculenta 



Astragalus crassicarpus Psoralea tenuiHora 



Astragalus mollissimus Stipa spar tea 



Cactus viviparus 



Large areas of sandy hills bearing this sort of vegetation are to 

 be found at present in Holt, Garfield, Rock, and Brown counties, and 

 along the northern boundary of the sandhills in Cherry and Sheri- 

 dan counties. These tracts are typically covered by a plant cover 

 which is much less open than the bunch-grass land although here 

 and there both of the dominant species show a poorly defined bunch- 

 grass nature. The association presents a noteworthy landscape 

 when the spear-grass is in fruit. The scattered stems with their 

 multitudes of straw-colored or whitened awns waving in the wind 

 above a loose or tufted sod appear from a distance not unlike a 

 thinly stocked wheat field at harvest time. Koeleria cristata is one 

 of the commonest grassy associates. Other grasses of importance 

 in this association as it occurs outside the sandhills are Agropyrum 

 pseudorepens and A. spicatum, but they are not commonly seen in 

 the sandhills variation of the association. 



Secondary species are found in considerable number. Within 

 the sandhills proper some of these are those that hold a similar 

 rank in other associations already described, while others are impor- 

 tant and conspicuous only within this association in its typical ex- 

 pression westward. One of the most widespread species is Mon- 

 arda citriodora which forms extensive societies characteristic of the 

 sandy plains along the western border of the sandhill region in 



