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THE VEGETATION OF THE HACKENSACK marsh: A TYPICAL AMERICAN FEN 



line or by a change in the tidal levels, which introduced brackish or saline 

 conditions again. 



Overlying the muck and covering the marsh surface is a dense mat of 

 roots, plant remains, and decaying organic material, which forms a sod ranging 

 from 2 inches to 4 feet in thickness (Fig. 2) . This sod, when dry, is extremely 

 hard and compact, and for this reason is used advantageously in dike-building. 



COMPARATIVE STUDY OF FEN VEGETATION (J. W. H.) 



Ecologic research has reached such a stage in. America that it is profitable 

 to compare the phytogeographic formations of North America with similar 

 ones of other lands. This comparative study is necessary in order to give us 

 clearer views of the causes underlying the distribution of plants with respect 

 to their habitat conditions. The author has recently paid considerable atten- 

 tion to this phase of ecologic research, and has printed one paper dealing with 

 ''American Heaths and Pine Heaths." He has had accepted for pubHcation 

 another comparative study of "Alpine Fell-fields in Eastern North America," 

 and he has the photographs and material assembled for another contribution 

 on "The Influence of Slope Exposure in Plant Distribution." The present 

 account of the ecology of the Hackensack Marsh, written in conjunction with 

 the floristic studies of Vincent G. Burns, is a fourth contribution to such com- 

 parative ecology. 



The vegetation of the Hackensack Marsh constitutes a number of plant 

 formations, two of the most important being the salt marsh formation and 

 the fresh-water marsh formation. In England the type of fresh-water marsh 

 represented in America by the part of the Hackensack Meadow controlled by 

 fresh water is called a fen. It is important, as ecologists, for us to have clear 

 concepts of the character of the units of vegetation in this and other countries 

 before we attempt to describe them. This desideratum is reached in part by 

 comparing the words used in different places for the same phytogeographic 

 formation. Sometimes the popular usage runs parallel with the exact scientific 

 appHcation of the name. At other times it does not become appHcable. The 

 terms "marsh" and "swamp," in common language, are frequently used 

 interchangeably. But phytogeographically speaking, marshes and swamps 

 are quite different, physiognomically and floristically. The two terms "moor" 

 and "fen" are often confused in England. A distinction must be made 



