Transition Prairie-Forest District. 523 
anthus rigidus (= H. scaberrimus), H. oceidentalis, Solidago Er S. missouriensis, Hieracium 
longipilum, Diplopappus linariifolius, Liatris eylindracea, L. scariosa, L. pyenosta re Prenanthes 
Nabalus) aspera, Gnaphalium polycephalum (= G. ee Chrysopsis villosa; lastly in 
September, Aster sericeus, A, azureus, A. oblongifolius, A. multiflorus, A. ericoides er Gentiana 
puberula. 
The grasses of dry prairies are Chrysopogon nutans, Andropogon fur- 
catus, A. scoparius, Koeleria cristata, Eatonia obtusata, Elymus canadensis, 
Stipa spartea and Sporobolus PETER The flora of such prairies in 
Wisconsin is peculiarly uniform, because the following grasses predomi- 
nate: Andropogon furcatus, A. scoparius, (see Fig. 27) Chrysopogon nutans, 
Fig. 27. Bunch-grass Formation. Andropogon scoparius Michx. together with Artemisia flifolia 
Torr. and the short grass Bouteloua hirsuta Lag. Photograph by Dr. H. L. Snantz with per- 
mission United States Department of Agriculture. 
Sporobolus asper, Bouteloua hirsuta and Festuca tenella. In depressions twenty 
feet below the general surface occur Agrostis scabra (= A. hiemalis), 4. 
perennans, Asclepias cornuti, Viola pedatifida, Ranunculus rhomboidens. 
The prairies in the neighborhood ot Chicago near Lake Michigan have 
had a swamp or lake origin. Aquatic floating plants such as, Riccia, Potamo- 
geton, Brasenia are supplanted by bulrushes, Srirpus lacustris, Typha, Ponte- 
deria, Sparganium, Sagittaria, Zizania, Phragmites, Acorus calamus and Erio- 
phorum cyperinum. Sedges later encroach on these plants as the new soil 
