STEUCTUUB OP THE FORMATION 57 



low the dense mass of yellow and green. In the vicinity oi' 

 old stock yai'ds, Cassia immediately takes full possession of 

 the denuded areas. Helianthus annuus and A mbrosia trifida 

 attain considerable prominence along the wet meadow for- 

 mation and in roadside ditches. Parts of the wet meadow 

 formation from which the grass is cut several times during 

 the year afford suitable location for such plants as Plantago 

 major, P. rugellii, Trifolium pratense, T. repens, and Poa 

 pratensis. Helianthus grosse-serratus and H. giganteus, 

 though not ruderal species, have found home-like conditions 

 on the banks of a ditch extending the entire length of the wet 

 meadow formation. 



SPECIES OF THE PEEVERNAL FLORAL ASPECT 



Principal Species 



Carex pennsylvanica. Antennaria campestris. 



Secondary Species 



Androsace occidentalis. Salix humilis. 



Anemone caroliniana. S. fluviatilis. 



Equisetum arvense, Corylus americana,. 



THE PUEVERNAL FLORAL .\SPECT 



The earliest prevernal bloomers of the prairie formation 

 appear on the southern slopes of the higher ridges during the 

 first or second week in April. Of the four species proper to 

 the formation, one, Carex pennsylvanica, not infrequently 

 ranks as a facies, and the others, Anemone caroliniarM, An- 

 tennaria campestris, and Androsace occidentalis, occur as 

 copious or gregarious species. Carex pennsylvanica is a xero- 

 phyte, forming patches or mats several meters in extent on 

 slopes or crests of ridges; toward the middle of April these 

 patches are rendered noticeable by the yellow and purple 

 of the numerous small spikes. Carex pennsylvanica also oc- 

 cur in low meado\\'S, where it grows with reduced numbers, 

 and blossoms about a week later, for which reason it never as- 



