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in sufficient quantity to change the color. The ground is protected 

 from the lake by the fringing dune. The ridges, which parallel the 

 bluff, are low (1-5 dm.) and usually free from blowing, but occa- 

 sionally small blowouts are developed. 



Ecological Characteristics. — The vegetation is essentially open, 

 and consists mostly of upright plants half a meter or more high. To- 

 ward tlie sides of the ridges, where the soil contains more humus, 

 are invaders of more typical prairie associations. The plants of this 

 association need a maximum of light and consequently do not long 

 withstand the shade of invading oaks. Yet the vegetation is rela- 

 tively so open that the Liatris scariosa association forms one of the 

 important pathways for the spreading of the oak woods. The sta- 

 tions of its best development are separated from the main body of the 

 oaks by the area of the pines. The latter has acted as a partial bar- 

 rier in retarding the development of the black oaks on the ridges be- 

 tween Waukegan and Beach. 



The Association. — This association has been named from its most 

 imposing species, blazing star {Liatris scariosa). This plant, with its 

 large purplish spikes, is thoroughly dominant in the serotinal and au- 

 tumnal aspects. During the estival and early serotinal seasons the 

 white blossoms of flowering spurge (Euphorbia corollata) are almost 

 equally conspicuous. A few other species of less importance are 

 typically charcteristic of the association, such as Castilleja sessiliHora, 

 Liatris cylindracea, lead plant (Amorpha canescens), bush clover 

 (Lespede^a capiiata), and black-eyed Susan {Riidheckia hirta). In 

 addition to these, almost any sand-preferring plant may be found in 

 greater or less abundance in this association. The lines of succes- 

 sion leading from this association may proceed to any of the three 

 provinces represented in this region. In the northern part of the 

 region the succeeding association is usually the oak forest; in tlie vi- 

 cinity of Beach it may be the heath or, to a much smaller extent, the 

 pine woods ; and near Waukegan it is usually the prairie associations, 

 such as the Liatris spicata, each one of which will be described later. 



LIST OF THE SPECIES OE THE EIATRIS SCARIOSA ASSOCIATION 



Dominant Species 

 Liatris scariosa Oenothera rhomhipetala 



Castilleja sessiliHora Lespede::a capitata 



Euphorbia corollata 



Secondary Species 

 Amorpha canescens Aster inultiflorus 



Acerates viridiHora Andropogon fnrcatus 



