Minnesota Plant Life. 471 



The prairie. A most characteristic xerophytic formation in 

 Minnesota is the prairie especially the high rolling prairie, 

 which differs considerably from ordinary meadow or pasture. 

 Much of the level prairie is mesophytic rather than xero- 

 phytic. Here a variety of grasses, pulses and composites grow 

 luxuriantly. Such a region is the home of tumbleweeds, com- 

 pass-plants and prairie turf-building varieties. Some strongly 

 xerophytic lilies, such as the onions, are found in profusion 

 upon the plains. Over unbroken prairie, between the plants 

 established upon it there exists a great competition. This 

 goes on not only between the under-ground portions, but also 



FIG. 232. The valley of the Minnesota river in the prairie district. Abundant grass vegetation. 

 After photograph by Professor R. D. Irving. 



between the erect structures. Thus, some prairie plants grow 

 tall and strong in order to get the light that they require. Sun- 

 flowers, indeed, may be regarded as the kings of the prairie. 

 Their erect, vigorous, annual stems are like trees as compared 

 with the more humble grasses, and where they occur in abun- 

 dance they may, to the seeing eye, be regarded, perhaps, as in- 

 dicative of how the forests of the world will appear hundreds 

 of thousands of years in the future. One may look forward 

 and imagine sunflowers and their kind grown taller and 

 stronger, a hundred feet or more in height, and even able to 

 usurp the place of the trees that are now abundant in the woods. 



