TYPICAL SWAMP AREAS. 61 
good portion of the year, immense thickets of Planera 
aquatica are formed. 
Sometimes these shrubs are small, forming an almostim- 
penetrable thicket, in other places the trees are larger and 
much farther apart. The downy red maple, Acer Drum- 
mondii, is a notable form as one goes from the swamp 
proper to higher ground. An interesting succession of the 
varieties of the ash may be observed in the progress from 
swamp to mesophytic conditions. Common in the swamp 
is found Fraxinus Americana profunda; on somewhat 
higher ground, Fraxinus viridis ; in mesophytie surround- 
ings, Fraxinus Americana. The largest of the very abun- 
dant trees in these marginal forests is the sweet gum 
(Liquidambar styraciflua ), and associated with it, white and 
red oaks, immense sassafras trees, Quercus Michauxii, Pla- 
tanus occidentalis, Gymnocladus Canadensis, Celtis Missis- 
sippiensis and Nyssa sylvatica. (Plate 20.) Among the 
shrubs are found Cercis Canadensis, Lindera Benzoin, Cor- 
nus paniculata, Asimina triloba, Ulmus alata, Morus rubra, 
Euonymus Americanus sarmentosus and Aralia spinosa. 
Among lianas are Tecoma radicans, Rhus toxicodendron, 
Bignonia capreolata and Ampelopsis quinquefolia. An in- 
teresting southern form found abundantly in these swamp 
lands is the cork tree (Leitneria Floridana). 
Inasmuch as we find here a meeting-point of the southern 
forms which have followed up the sluggish tributaries of 
the Mississippi, and the northern forms which are migrat- 
ing southward, the farther study of this area is tikely to 
prove intensely interesting. The difficulties attending the 
separation of these floras ecologically and assigning each 
part its position, on account of climatic, topographic or 
moisture conditions, are many, and such a discussion will 
find no place in this paper, which, as stated in the outset, 
is intended to be a collection of reliable data concerning 
these swamp areas. 
