AN ARTIFICIAL PRAIRIE* 



B. SHIMEK 



Seven-eighths of the area of the State of Iowa and large por- 

 tions of surrounding states were originally covered with prairie. 

 The greater part of this area has been completely transformed 

 by cultivation and the prairie flora has disappeared excepting 

 along highway's and the right of way of railways, and in certain 

 rougher parts of the state which are not cultivated. 



The original prairie was here with all its peculiarities when 

 the white man came, and it had probably long existed in the 

 condition in which he found it. There is no record of its cause 

 or origin excepting as we find it in the forces and phenomena of 

 the natural world, and these have been so variously interpreted 

 that the origin of the prairies has been ascribed to a variety of 

 causes, t 



The writer has contended § that evaporation as influenced by 

 exposure to temperature and wind, and by relative humidity, 

 was the chief and most universal cause of the treelessness of the 

 prairie, the forest plants failing in exposed places because they 

 are mesophytie, while the prairie plants are able to hold their 

 own in such places because they are structurally adapted to ex- 

 istence under conditions which are, at least during a part of the 

 summer, decidedly xerophytic. 



An interesting bit of evidence supporting this view is fur- 

 nished by a strip of prairie bordering a highway near Home- 

 stead, Iowa, which differs from ordinary prairie in that it has 

 been developed within the memory of men now living and under 

 conditions which make it essentially an artificial, man-made 

 prairie. It is not of great extent, but extent of area does not 

 form a measure of the prairie, the latter being marked by only 

 one consistent feature, the flora. 



*This paper was presented in substance before the Botanical Society of America at 

 Cleveland, 0., December, 1912. 



tSee the -writer's paper on "The Prairies" in this volume, pp. 169-240, 1911. 



§The Prairies, ibid. 



VI— 4 — 4 3.5 



