PLANT ASSOCIATIONS OF WESTERN PENNSYLVANIA 



115 



dulatum, Moneses uniflora, Cypripedium acaule, Mitchella re- 

 pens, Arisama triphyllum, Tnentalis americana, Sambucus 

 racemosa, etc. 



Tsuga frequently develops in so close a formation that it 

 inhibits practically all herbaceous undergrowth, but more com- 

 monly the stand is of the above composition in which the dom- 



Fig. 3. Narrow mesophytic ravine. The chief representatives here are 

 Tilia americana, Quercus rubra, Acer rubrum, and Castanea deniata. 



inant forms, both tree and herbaceous, are evergreen. It fre- 

 quently happens that one encounters a few forms of Tilia, Acer 

 rubrum, Fraxinus americana, and Castanea dentata associated 

 with the evergreen assemblage. 

 Deciduous Type. The development of the deciduous type of 



