Cm. VIII] COLD TEMPERATE GRASSLAND FORMATIONS 597 



Except in dry places the prairie-grass formation forms a continuous sward, with 

 Sporobolus asperifolius, Koeleria cristata, Eatonia obtusata, and Panicum Scribneria- 

 num as dominant species. As the season changes, the formation presents the guise 

 of spring and of summer and autumn alternately. During the spring the prairie 

 consists chiefly of grasses, among which numerous early-flowering plants are 

 scattered. Some of them, such as Draba caroliniana, Androsace occidentalis, Scutel- 

 laria parvula, and the exceedingly common Antennaria campestris, have inconspicu- 

 ous flowers; others, such as Peucedanum foeniculaceum and Carex pennsylvanica, 

 have small blossoms, which, however, are united into many-flowered yellow 

 inflorescences ; species with large flowers on higher situations are, in particular, 

 Astragalus crassicarpus, Baptisia bracteata (Leguminosae), Anemone caroliniana, 



Fig. 335. Natural prairie, Lincoln, Nebraska. 375 meters above sea-level. March. In the 

 background : the prairie-grass formation. In the foreground : cart-tracks with Andropogon — their 

 constant attendant. From a photograph by Bessey. 



Comandra umbellata (Santalaceae), but in lower situations are Allium mutabile, 

 Callirhoe alcaeoides (Malvaceae), C. involucrata, Lithospermum angustifolium, Viola 

 pedatifida. The garb of summer and autumn is chiefly determined by numerous 

 flowering plants. In particular there are numerous species of Amorpha, Solidago, 

 Verbena, Kuhnistera (Leguminosae), and, during the early autumn, species of Aster 

 and Lacimaria (Compositae). 



The very low, completely continuous sward ol the dry buffalo-grass forma- 

 tion is often formed exclusively of Buchloe dactyloides (Fig. 336). Other 

 grasses (Boutcloua curtipendula and B. oligostach3 T a) are feebly represented, 



