54 STUDIES IN THE VEGETATION OF THE STATE 



STRUCTURE OP THE FORMATION 



Within the limits of this prairie one hundred and eighty- 

 eight species are noted, of which eighty are elements proper 

 to the prairie formation, fifty-seven are peculiar to ravine, 

 meadow, and swamp, twenty-one are elements derived from 

 woodlands and thickets, and thirty are adventitious or rud- 

 eral species. When the diversity of the formation is consid- 

 ered, the facies are relatively few in number. Andropogon 

 scoparius is the important facies on the slopes and crests of 

 ridges and is always accompanied by A. furcatus, which 

 ranks next in importance. Throughout its entire range An- 

 dropofjon scoparius resorts to the "bunch" habit but once or 

 twice, viz., on steep, exposed, gravelly slopes to the west and 

 southwest of Great ridge. Everywhere else it plays the role 

 of a "sod-former," giving rise to a closed formation. Toward 

 the foot of ridges and in low prairie, Andropogon scoparius 

 and A. furcatus become of equal importance. Bouteloua curti- 

 pendiila and Koeleria cristata are also facies. Frequently 

 Bouteloua does not blossom, in which case it is likely to be 

 confused with Andropogon. Stipa spartea becomes a 

 facies in but one location in low prairies, where for a few hec- 

 tares it is almost exclusive. In the meadow formation, Andi'O- 

 pogon furcatus attains its maximum in size and numbers. In 

 somestationsitbecomesthesole facies ; again it shares equally 

 with two tall-growing meadow grasses, Chnjsopogon avena- 

 ceus and Panicum virgatum. Panicum is controlling in the 

 wetter parts of the formation, in the beds of draws, etc. Spar- 

 tina cynosuroides occurs in meadow formations sparingly 

 scattered throughout, never in numbers sufficient to rank as 

 an important facies. In the wet meadow formation Elcooharis 

 palustris covers the ground with a dense carpet-like layer 

 during May and June. This is soon hidden from view by the 



