Pool: THE VEGETATION OF THE SANDHILLS OF NEBRASKA 299 



Linum sulcatum 

 Lotus americanus^ 

 Lycopus lucidus 

 Ly thrum alaturn^ 

 Meibomia canadensis 

 Muhlenhergia racemosa 

 Naum bergia thyrsiflora^ 

 Panicum dichotomum 

 Panicum implicatum 

 Panicum scribnerianum 

 Psoralea argophylla 



1 Relicts. 



Psoralea tenuiflora 

 Ratibida columnaris 

 Rudbeckia hirta 

 Silene antirrhina 

 Solidago canadensis 

 Solidago rigida 

 Solidago serotina 

 Sorghastruni avenacenm 

 Thalictrum purpurascens 

 Viola obliqua ^ 



2 Invaders. 



I have chosen to call this type the hay meadow association 

 because of its very important economic relation. It must not be 

 supposed, however, that all of the hay of the region is made from 

 this association. A considerable quantity of this product is har- 

 vested from certain upland associations, and, indeed, especially dur- 

 ing the drier years, much of the area occupied by the rush-sedge 

 wet meadow association is cut over and made to yield much valuable 

 hay. The latter association, as a rule, covers a substratum too wet 

 to permit of hay-making operations with the average rainfall, but, 

 although the hay is somewhat inferior, it becomes of much value in 

 times of drought when the usual meadows are "short." 



Because of the large number of grasses in these meadows that 

 reveal little or no striking alternation, the association exhibits a 

 rather homogeneous structure. As Pound and Clements state the 

 meadow associations are typically closed and the dominant plants 

 are relatively long-stemmed, sod-forming species. This condition 

 stands in marked contrast to that seen over the bunch-grass uplands. 

 A uniformly developed grassy cover, in which the above dominant 

 species compose a layer varying in height from one-half yard to one 

 and one-half yards, revealing beneath the presence of numerous 

 principal and secondary species of showy natures, is the typical 

 expression of the hay meadows as found in the sandhill region. 



The dominant species and their associates are markedly reduced 

 in number and abundance as the meadow becomes higher and drier 

 and approaches those conditions known as "dry valleys" in which 

 short-grasses are not infrequently found. The great number of 

 mesophytic species lag behind as these situations are reached, and 



