THE PEAIEIES 1S7 



flora, for in the localities represented we find various t^'pes of 

 topography and geological formations, yet the flora is prac- 

 tically the same, and this flora is the best ear-mark of the 

 prairie. 



Some of the species reported herein as belonging to the prairie 

 are occasionally found in the woods, but so far as the writer's 

 observation goes, almost uniformly in more or less open places 

 where there is exposure to the sun and wind, and where topogra- 

 phy and soil permit of rapid run-off or evaporation of water, — 

 hence where the conditions are at lea.st in part xeroph^•tic. Places 

 of this kind are simply a step toward the ''oak-barrens" or 

 "oak-openings'*, whose edges they exactly simulate. Otherwise 

 individuals only of these prairie plants find their way into 

 forested areas, and that rarely. 



Likewise no^ only forest trees but also herbs of the forest fail 

 to appear on the open prairie. There is indeed very little ming- 

 ling of these two floras except in the narrow border belts already 

 mentioned, and few species are found in both situations. The 

 latter are foreign and native herbs and shrubs several of which 

 have become well-established weeds. The most common of these 

 are the following: 



Chenopodium albiiin L. Silene stellata (L.) Ait. f. 



Nepeta cataria L. Taraxacum officinale Weber 



Oxalis stricta L. Veronica virginica L. 



Rhus glabra L. Vitls vulpina L. 



Ehus toxicodendron L. Zanthoxylum americanum Mill. 



Taken as a whole the floras of the forest and prairie are strik- 

 ingly different.^ 



As noted, some variations may be observed in the prairie flora, 

 but this occurs practically within the limits of the prarie list 

 and is of equal extent on each of the types or kinds of prairie 

 areas. The major part of the flora of all these types is the same. 

 and constitutes one of the most distinctive characteristics of all 

 prairie. 



* For a more detailed comparison of the prairie flora and the floras of 

 other habitats see the botanical report on Harrison and Monona counties 

 in the Eeport of the Iowa Geological Survey, vol. XX, 1910. 



