442 Part IV. Chapter 2. 
Fresh Water Marsh Formation. 
These formations are frequent in the southern states where so many rivers 
rising in the mountains flow eastward and southeastward to meet the ocean. 
Briefly we may distinguish the following formations and associations. 
Reed Marsh Formation. This is typic along rivers in Virginia and else- 
where. — Typha-Sagittaria Association. The larger rivers are fringed 
by a narrow belt of marsh vegetation which merges into salt marshes down 
stream and into the wooded swamps above. Such trees as Tarodium distichum, 
Acer, Magnolia, Salix nigra occur associated with bushes of Alnus rugosa, 
Salıx longipes, Itea, Rosa carolina, Clethra and with certain lianas (Smulaz, 
Berchemia, Clematis). The outermost growth in water 6—ı0 inches (155 
30 centimeters (deep is most often denominated by 7ypha latifolia, Sagittaria 
lancifolia, Pontederia cordata, while Scirpus lacustris, Zizania aquatica, Sium 
cicutifolium, Polygonum hydropiperoides are ordinarily abundant elements in this 
association. Acorus calamus sometimes grows in almost pure association, while 
in limited areas Juncus effusus fringes open water as does Dianthera americana 
in other places infested with Cuscuta Gronowi. 
Scirpus-Erianthus Association. The edges of the hydrophile forest 
are occupied by an association in which Scarpus cyperinus var. eriophorum 18 
the most important element with Erianthus saccharoides, Typha, Andropogon 
glomeratus, Woodwardia and Arundinaria Zecta. — Along the ditches and 
pools in the heart of the Dismal Swamp Dulichium arundinaceum and Tria- 
denum virginicum are abundant in the shallow water. 
Low Marsh Formation. This formation includes the limited areas of 
marshy ground or swales in the forested plain which are chiefly covered with 
a low rather than a tall reedy growth, — Rhynchospora-Eleocharis Asso- 
ciation. The vegetation of the low marshes in Virginia comprises a great 
variety of species among which occur: Rhynchospora cymosa, R. inexpansa, R. 
glomerata, R. corniculata, Eleocharis ovata, E. tortilis, Carex verrucosa, Fimbri- 
stylis autumnalis, F. laxa, Lipocarpha maculata, Fuirena squarrosa, Cyperus- 
Juncus-species, Xyris carolimana and ambigua. Grasses mostly with weak 
stems are often an important element: Glyceria pallida, Panicum gibbum, P. 
verrucosum, P, viscidum. 
Aquatic Formations. This unlike most of the other formations presents NO 
clearly defined associations corresponding to topographic conditions. On the 
contrary, the distribution of aquatic plants seems to be largely determined by 
accidents of dissemination. The greater part of the aquatic vegetation occupies 
lakes, ponds, open ditches, river channels and bayous throughout the region. 
Elodea canadensis grows in the swifter reaches of the streams. Myriophyllum 
heterophyllum, Nymphaca odorata, Utricularia purpurea, U. inflata, Callitriche 
heterophylla are among the most common aquatics of the region. KRiccia Fn- 
fans, often growing terrestrially, is abundant. Ludwigia (Isnardia) palustris, 
Juncus repens are also aquatic marsh plants. — Ponds in Georgia are surroun- 
