108 OUTLINE OF PLANT GEOGRAPHY 



common, as well as a number of Leguminosae, e. g., Amorpha can- 

 escens, Baptisia, Mclilotus. 



The prairie reaches its most typical development in western 

 Iowa, eastern Kansas and Nebraska, 1 and the Dakotas. The 

 grass flora comprises over 30 species, but there are many other 

 herbaceous plants, of which the most abundant are various Com- 

 positae, sun-flowers, Coreopsis, iron-weed (Vemonia), asters and 

 golden rods, worm- wood (Artemisia), and others. Anemones, 

 larkspurs, phlox, verbena, oxalis, flax, blue-eyed grass (Sisyrinch- 

 ium), milkweeds (Asclepias), are characteristic, as well as others 

 including several genera of Leguminosae, e. g., Desmodium, As- 

 tragalus, Baptisia. 



The only woody plants belonging properly to the prairie of 

 this region are a dwarf willow (Salix humilis) and a rose {Rosa 

 Arkansana). 



Along the streams, willows and cotton- woods are found, but 

 these do not invade the prairie. Of course much of the original 

 prairie has been broken up, and is now covered with the great 

 wheat and corn fields of the midwest. 



The constitution of the prairie of Nebraska has been very 

 thoroughly studied. 2 There are two types, depending on soil 

 conditions. On loamy soils there is a close sod composed of 

 several species of grasses, e. g., Sporobolus, Koeleria, Eatonia, 

 Panicum; on heavy clay is the buffalo-grass formation, where 

 " bunch grasses" form separate mats or large tufts, with bare 

 ground between. The most important of the bunch grasses are 

 the buffalo-grass (Buchloe dachjloides) and " grama-grass " (Bout- 

 eloa oligostachya). Buffalo-grass formation is typical of most of 

 the western cattle ranges. 



A good many secondary species of grasses, as well as various 

 other plants may occupy the space between the prevailing bunch 

 grasses. One of the common grasses, Stipa comata, at once at- 

 tracts attention by its conspicuous silvery plumes. Occasionally 

 a small yucca or cactus suggests the still drier plains further west. 



Toward the north the true prairie reaches to the foot of the 

 mountains which rise abruptly from the rolling prairie. This is 



1 Pound, Roscoe and Clements, F. E., Botanical Gazette, XXV, p. 384, 1898. 



2 Harshberger, loc. cit., p. 526. See also Woodard, J., in Botanical Gazette, May, 

 1924. 



