478 PLANT ASSOCIATIONS 



The swampy thicket zone contained mostly shrubs and small 

 trees, including an alder, a blueberry, a pepper bush (Clethra), 

 gray birch, and red maple. 



The arid soil zone contained more than twenty species, mostly 

 sand-frequenting annual seed plants. 



The meadow was growing under artificial conditions, and it 

 was merely noted that its flora consisted mainly of cultivated 

 grasses. 



The dry woodland zone contained some twenty-three con- 

 spicuous forms. The three principal trees, in the order of their 

 numbers (omitting the region d), were white pine, northern pitch 

 pine, and red oak. The forest floor contained an abundant growth 

 of shrubs and herbs. At least five species of the latter were 

 common to the woodland zone and the arid sand zone. 



The marked differences in the character of the vegetation 

 of the several zones were almost wholly due to differences in 

 the amount of water supply. Not only would the trees have 

 died if transplanted into the pond, or the pond aquatics have 

 died if removed to the dry sandy soil of the woodland, but in 

 general each set of plants was better off in its own zone than it 

 would have been in any other. The sand-pit flora was, however, 

 only a short-lived succession, soon to be followed by the wood- 

 land flora. 



456. Similar vegetation due to similar conditions. As soon 

 as one begins to collect plants in a set of localities new to him, 

 he often discovers that his old acquaintances are still to be found 

 grouped as he has been accustomed to see them. The muddy 

 borders of ponds from Maine to Minnesota and beyond are 

 fringed with the same kinds of bur reeds and sedges, set with 

 water plantain and decorated with the soft white blossoms of 

 the arrowhead. The sand dunes along the northern Atlantic 

 coast and those that border Lake Michigan are clothed with a 

 sparse vegetation, which in both cases includes the little beach 

 plum, such coarse grasses as that shown in Plate I, and the 

 straggling sea rocket. Barnyards and waste grounds about farm 



