160 THE PLANT LIFE OF MARYLAND 



is generally high, so that the most mesophytic forms of herbaceous 

 vegetation are found. 



Maple-Gum Association, — This title is meant to include the highly 

 mesophytic assemblage found in depressions or valleys of the up- 

 lands. A glance at Table 1 will show that in such places neither 

 oaks nor hickories prevail but that their dominant place is taken 

 by the Sweet Gum and the Eed Maple, with the Tulip-Tree as the 

 next most important constituent. Equally characteristic though not 

 present in such large numbers are the Beech, the Swamp Oak, the 

 Black Gum and the Buttonwood and in the moister places, the 

 River Birch and the Sweet Birch. The White Oak and Black Oak 

 by no means disappear, and the Willow Oak is found in many 

 cases. The Tulip-Tree, the Beech and the oaks are the trees on 

 the tension line between the depressions and the higher parts of the 

 area; Sweet Gum also occurs on fairly high ground, but not in large 

 numbers, while Maple, Buttonwood and Birch fail to spread up- 

 ward along the slopes to any extent. Certain other trees of a highly 

 mesophytic type find the necessary moisture and shelter in such 

 places; e. g\, the Bed Mulberry, the Elm, the Black Walnut, and 

 the White Ash. The lower zone of this association is quite typical, 

 including: 



Cornus fioruht 

 Sassafras sassafras 

 Ilex opaca 

 Aralia spiimxtt 

 Asimina triloba 

 Magnolia virgin mint 

 Cercis canadensis 

 Carpinus caroliniana 

 Alnus rugosa 

 Sambucus canadensis 

 Pieris mariana 

 Clethra alnifolia 

 Corylus americana 

 Benzoin benzoin. 



