THE PRAIRIE-PLAINS CLIMAX. 



215 



as Lesguerella alpina, Hedeoma, Eriogonum, etc., become dominant in every 

 open commvmity. The grasses, especially Aristida and Stipa, soon enter, the 

 nmnber of herbs increases rapidly for a time, and then decreases as the climax 

 Bovieloua curtipendula and B. oligosfachya become dominant. 



Gleason (1907 : 157) has described the successional relations of the bunch- 

 grass, blow-sand and blow-out associes, and the black-jack forest associes of 

 Illinois: 



THE FOREST FORMATION 

 9 



THE SWAMP FORMATION 

 7 



u 



Swamp 

 Assoc 



THE PRAIRIE 



THE PRAIRIE FORMATION 



PROVfNCE 



THE BLOWOUT FORMATION 



Fio- 7. — ^Psanunosere in central Illinois. After Gleason. 



The bunch-grass dominants are Eragrostis trichodes, Stipa spartea, and 

 Panicwm spp., with which are associated Calamovilfa, Sporobolm, Bovtehua, 

 etc. The blow-sand associes consists of Cydoloma, Cristatella, Cassia, etc. 

 It is a stage in the development of the blow-out to prairie. The sequence is 

 as follows: (1) Cassia-Ambrosia-Cydoloma (blow-sand); (2) StenophyUus- 

 Panicum-Sorghaslrwm, (2a) Populus-Acer (blow-out); (3) Cladonia-Antm- 

 naria; (4) Heliardhus-Hieracmm (prairie). 



