56 STUDIES IN THE VEGETATION OF THE STATE 



cal xerophyte reduced in size of leaf surface. L. scariosa 

 frequents low prairies and extends about half way up the 

 ridges, while L. pycnostachya is a tall species, invariably in- 

 habiting meadow formations. Baptisia bracteata and B. leu- 

 cantlui arrange themselves in concentric zones, ten to thirty 

 meters wide, about draws and meadows and about ridges. 

 The taller, glabrous form, B. leucantha, always occupies the 

 moister zone, and it is seldom that one finds individuals of the 

 one species within the zone of the other. B. bracteata is fre- 

 quently found half way up the slopes. Erigeron ramosus 

 finds the most favorable conditions on the tops of ridges and 

 southern exposures. Euphorbia corollata is a gregario-copi- 

 ous plant, found mostly on ridges and slopes. It gradually 

 diminishes in numbers as the foot of the ridge is approached, 

 and hardly occurs at all in meadow formations. 



Certain thicket and open woodland species have established 

 themselves in the prairie and meadow formation. Among 

 these are Aster azureus and A. levis, two gregario-copious, 

 rosette-forming species, which thrive abundantly in low prai- 

 ries. Corylus americana has gained a foothold at several lo- 

 cations in the formation, particularly near the creek and 

 hedges. This species takes up its characteristic thicket 

 growth, which makes possible the migration of such woodland 

 forms as Ratibida pinnata, Silene stellata, AcalypKa virgin- 

 ica, Helianthtis tuberosum, Monarda fistulosa, and Heliopsis 

 scabra. The invasion of Corylus in a prairie formation clear- 

 ly demonstrates its superiority of occupation over the prairie 

 species. With Corylus also are found a few specimens of 

 Bamhueus canadensis, Cornus a^perifoUa, Rhus glabra,, Quer- 

 cus macrocarpa, and Fraxinus lanceolata. 



Of the ruderal species the aianthous Cassia chaviaecrista 

 is the most conspicuous during its flowering period, as well as 

 the most important in numbers. To the south along the sec- 

 tion road. Cassia has pushed into the prairie formation twen- 

 ty-five to thirty-five meters, and in many places the prin- 

 cipal and secondary species have been crowded out ; even the 

 facies are subordinated, and to find them one has to look be- 



