158 



across the country, by rail and on foot, is that the two are 

 about equal in extent. 



THE BUNCH-GRASS ASSOCIATION. 



Through the prairie formation the bunch-grass association 

 is the prevailing one, covering alike the level areas of sand and 

 the dunes, and broken only by cultivated fields or by blowouts 

 and blow-sand. The association derives its name from, and is 

 characterized by, several species of grasses which grow in com- 

 pact stools or bunches varying from a foot to two feet in diam- 

 eter. They are not crowded so closely as to produce a sod, as in 

 the typical Illinois prairies, but stand a little distance apart, 

 thus making the bunch character prominent (PI. XVIII., Fig. 1 ). 

 There is but little of the bunch-grass prairie remaining in its 

 original state, most of it having been pastured with horses or 

 cattle, which by their grazing have greatly changed the char- 

 acter of the vegetation. Southeast of Bath there is a field 

 which has apparently never been pastured (PL VIIL, IX.), and 

 the following description of the original type of bunch-grass 

 prairie is based on its character there and on small strips along 

 the railroads. 



The principal grasses are Eragrostis t /■/diodes, Stipa spartea, 

 Panicum cognatum, and an undetermined species of P<inicii//i. 

 The first two species produce large loose bunches, one to two 

 feet in* diameter and almost as high, with the culms rising to a 

 height of three to five feet. Panicum cognatum grows in dense 

 fiat bunches scarcely afoot high, exclusive of the widely spread- 

 ing panicles, and the undetermined Panicum is even lower, with 

 the basal leaves and culms almost prostrate. Tricuspis sesleri- 

 oides, with loose bunches much like those of Eragrostis trichodes, 

 is abundant in some places, especially near the edge of timber ; 

 ( ■alamovilfa longifolia, with culms six feet high, occurs sparingly 

 in patches ; and Eragrostis pectinacea, Bouteloua hirsuta, Pani- 

 cum virgatum, Paspalum setaceum, and Sporobolus cryptandrus 

 also produce more or less well-developed bunches. Carex grav- 

 ida and Cyperus Schiveinitzii have tufts of basal leaves from 

 which several culms arise, and may also be grouped with the 



