191 



*Allionia nyctaginea * Ambrosia psilostachya 



Anemone cylindrica Hie, ■(((■'mm longipilum 



*Lesquerella spathulata *Kuhnia glutinom 



*Gristatella Jamesii *Chrysopsis camporum 



*Polanisia graveolens Solidago missouriensis 



Baptisia bracteata Helianthus scaberrimus 



Amorpha caneseens Coreopsis palmata 



This group in the prairie formation is obscured by the 

 presence of 65 species, or 56 percent, of eastern distribution, 

 to be regarded as derivatives of the Atlantic floral element; and 

 the remaining 18 species, or 15 percent, include 9 of transcon- 

 tinental distribution, 4 introduced species, 2 (* Aristida tuber- 

 culosa and * Sporobolus cryptandrus) with a range along the 

 coast of the Atlantic and Great Lakes and locally in the interior, 

 and 3 whose range is local or unknown, namely, *Panicum sp., 

 Phlox bifida, and Antennaria sp. 



The importance of the Sonoran element can be shown to 

 better advantage by excluding all those species which occur 

 commonly in other associations in the state, limiting the list to 

 the plants most characteristic of the sand region. Of the 28 

 species thus selected, 1 is local, 2 range along the coast and the 

 Great Lakes, 6 are eastern or southeastern, and 19, or 68 per- 

 cent, are western or southwestern. In the preceding list and 

 in the paragraph following it, 22 of these species are marked 

 with an asterisk. The 6 eastern species included are 



Panicum cognatum Polygonum tenue 



Cyperus Miculmis Monarda punctata 



Salix tristis lonactis Unariifolius 



The 66 species of the sand region which are found only in 

 the black-jack association include 1 of local distribution. Heli- 

 anthus illinoensis; 1 introduced species, Chcetochloa viridis\ 9 of 

 western distribution; and 55 of eastern and southeastern range, 

 indicating plainly the eastern relationships of the flora, and 

 the floral similarity of the black-jack to the other forests of 

 central Illinois. Of these 55, all but one, Polygonum cristatum, 

 occur also in other plant associations within the state, while of 



