554 
the habitat range of any species is more extensive when the biotic factors 
of competition are removed than when they are present. The numerous 
disturbances accompanying civilization usually eliminate the influence of 
biotic factors, at least in part, and admit not only a greater prominence of 
secondary species but also a wider edaphic range of all species than 
existed under natural conditions. Recently drained sloughs may be 
found in which Spartina still persists as the dominant plant, but the 
Spartina association in such cases may have as secondary species mostly 
plants characteristic of the Andropogon associations. It is obvious that 
a detailed account of associations under disturbed conditions is not only 
valuless but is confusing to the uninitiated. Secondary species of local 
prominence following drainage, grazing, or other disturbance are not in- 
cluded in the list below unless they were found to occur frequently in the 
same associations elsewhere. A more complete list of secondary species | 
of any association may be obtained from the annotated list beginning on 
page 559 of this article. 
The Scirpus fluviatilis Association—Scirpus fluviatilis, S. validus, 
Glyceria septentrionalis, Sparganium eurycarpum, Acorus Calamus, 
Sagittaria latifolia, Sium cicutaefoliwm, Pontederia cordata, Alisma 
Plantago-aquatica, Rumex verticillatus, Polygonum Muhlenbergu, P. 
hydropiperoides, P. amphibium, Eleocharis palustris, E. acicularis, Pen- 
thorum sedoides, Scutellaria galericulata, Ludvigia palustris, Mimulus 
ringens, and Ranunculus delphinfolius. 
Typha latifolia and sometimes Phragmites communis occur in this 
association when there has been some disturbance, such as tramping by 
grazing animals, pollution of the water, and dredging. With continued 
disturbance Scirpus fluviatilis disappears, and Typha latifolia dominates 
except for small colonies of Phragmites communis in some localities. The 
data obtained in this survey indicate that neither Typha nor Phragmites 
was abundant in the natural prairies of the state. Scirpus validus may 
form an association in deeper water beyond Scirpus fluviatilis. In the 
shade of trees Sagittaria latifolia usually replaces Scirpus fluviatilis. 
Forest invasion of this association may occur. The principal invad- 
ing species noted are Cephalanthus occidentalis, Cornus stolonifera, 
Salix amygdaloides, S. nigra, S. cordata, S. discolor, and S. longifolia. 
The Carex Association—This association needs considerable more 
attention than it received during this survey. Carex vesicaria appears 
to be the most important dominant species on flood-plains and in some 
of the morainal depressions, but other species were also noted as domi- 
nants, namely, C. lanuginosa, C. stricta, C. Sartwellii, and C. vulpinoidea. 
The secondary species are: C. rostrata, C. lupulina, C. tribuloides, C. 
straminea, C. stipata, C. pennsylvanica, Scirpus atrovirens, Lobelia 
cardinalis, Steironema lanceolatum, Veronia fasciculata, V. altissima, 
Eupatorium perfoliatum, Asclepias incarnata, Stachys tenuifolia, Eleo- 
charis palustris, E. obtusa, E. intermedia, Leersia oryzoides, and Phalaris 
