394 BOTANICAL GAZETTE [JUNE 
The grass formations are more or less intermediate between 
the sand hill and the foothill formations, and serve to connect 
the two regions. The facies are two, Stipa comata and Agropyron 
pseudorepens each giving character to a more or less distinct type. 
The Stipa formation predominates over high prairies, the Agro- 
pyron formation upon level, sandy plains. The first exhibits a 
striking group of secondary species, which, from their constant 
association, and the uniformly blue color of their flowers, lend a 
distinctive character to the formation. These are Lupinus plat- 
tensis, Astragalus mollissimus, A. adsurgens, Spiesia Lamberti and 
Psoralea argophylla. The Agropyron. formation is much more 
open than the preceding, and is of a more indefinite type. 
Halophytic and ruderal formations play a more or less 
prominent part in the constitution of the floral covering of the 
prairie province, but they are rarely characteristic, and hence 
scarcely within the scope of a short paper. 
THE UNIVERSITY OF NEBRASKA. 
EXPLANATION OF PLATE XXI. 
Sketch map of the “Prairie Province:” I, the prairie region; II, the 
sand hill region; III, the foothill region, 
