368 MINNESOTA ROTANICAL STUUIKS 



socies are longer-lived than Popiilus and Bclitia enables them to 

 crowd out the latter in competition. 



Consocies : This association is represented by the following 

 species : 



Acer saccharum Qucrcus rubra 



Fraxinns lanceolata Tilia americana 



Qucrcus macrocarpa Uhnus americana 



These are usually well mixed, and the exclusive dominance of 

 any one of them is rather exceptional, although within small areas 

 Acer, Tilia or Qucrcus may be present in far greater numbers than 

 any other of the usual consocies. In very sandy soil and further 

 northward, Acer disappears and species of Qucrcus become more 

 abundant. 



Secondary species : In the upper or dominant layer may be 

 found with the consocies occasional trees of Betula papyrifera, B. 

 lutea, Populus deltoides, P. balsamifera and Ulmtis fulva. Some of 

 these, such as Betula and Populus, have persisted from the preced- 

 ing associes. 



The usual small trees and shrubs of this associes are : 



Acer spicatum Rhus rydbcrgii 



Amelanchier canadensis Ribes ainericanum 



Cornus stolonifera Ribes cynosbati 



Corylus americana Ribes gracile 



Crataegus macrantha Rosa blanda 



Crataegus punctata Rubus strigosus 



Crataegus rotundifolia Syniphoricarpos occiden- 

 Ostrya virginica talis 



Parthenocissus quinquc- llburnum opulus 



folia Fit is vulpina 



Prunus americana Xanthoxxlum americanum 

 Prunns virginiana 



Forming thickets along the edge of the woods, Prunus ameri- 

 cana, P. virginiana. Rhus glabra, R. hirta, Corylus americana, Cor- 

 nus stolonifera, C. paniculafa, Ribes gracile, Rosa blanda, Rubus 

 strigosus and Symphoricarpos occidentalis occur commonly. Prunus. 

 Rhus and Corylus usually form families or colonies. The others 

 usually occur in mixtures and rarely form families or colonies. In 



