343 



loamy. These thickets grow in and around the borders of the pines, 

 effectuahy cutting off their chances of reproduction. The central 

 parts of the thickets are too dense for the ecesis of oaks, but towards 

 the edge, where it is more open, black oak, Quercus velutina, quite 

 readily obtains a foothold and in time replaces the thicket. 



The marked differences between these two kinds of thickets are 

 the possession of lianas and the sandy-appearing soil in the Primus 

 thickets, while the Popiiliis-Salix-Cornus thicket, with virtually no 

 exceptions, is free from lianas and has somewhat loamy or mucky 

 soil. 



LIST OF THE SPECIES OE THE PRUNUS THICKET ASSOCIATION 



Dominant Species 



Pninus pumila Primus mrginiana 



Pnmus serotina Sainhucus canadensis 



Secondary Species 

 Lianas : 

 Vitis vulpina 

 Celastriis scandens 



Herbaceous plants 

 Anemone canadensis 

 Asparagus officinalis 

 Aster spp. 

 Fragaria virginiana 



Relic Species 

 Calainoznlfa longifolia 

 Buphorhia coroUata 

 Oenothera rhomhipetala 

 Phlox pilosa 

 Poa compressa 

 Potentilla frnticosa 

 Solidago nemoralis 



Invading Species 

 Quercus velutina 



Rhus toxicodendron radicans 



Lathyrus venosus 

 Veronica virginica 

 Melilotus alba 

 Rosa huniilis 



Artemisia caudata (few) 

 Juncus balticus littoralis 

 Koeleria cristata 

 Petalostemum purpureum 

 Salix glaucophylla 

 Polvgonatuni hiHoruui (where 

 oaks have been cut) 



Up to the present point, the discussion of associations has been 

 limited to those of the sand-plain. The bluffs which constitute its 

 western boundary are tenanted by arboreal associations which show 

 an inclination to invade the prairie, although, up to the present 



