130 THE PLANT LIFE OF MARYLAND 



gradual nature of all these transitions makes somewhat artificial 

 an attempt to treat the two classes of Marshes separately. 



The topography of the upland determines largely the extent of 

 the Marshes. Where there is a very gradual shelving of the sur- 

 face from below tide level to a flat upland there are the largest 

 marshes, as in southern Dorchester County, where one may pass 

 from the shores of Fishing Bay over three to five miles of Marsh 

 before reaching the upland. In such localities may be observed the 

 transition from Salt to Fresh Marsh above noted, while the nar- 

 rower fringes of Salt Marsh abut directly upon a higher upland 

 without intervening Fresh Marsh. On the Choptank River, Eastern 

 Bay and Chester River and their tributaries the Salt Marshes are 

 not extensive, while in the Sassafras, Bohemia, Elk and North East 

 rivers the halophytic element is almost entirely absent. 



The usual precession of plant habitats observed in passing up one 

 of the longer rivers of the Eastern Shore, as the Nanticoke or Chop- 

 tank, is (1) Salt Marsh abutting directly upon the upland, (2) 

 Salt Marsh with Fresh Marsh lying between it and the upland, 

 (3) Fresh Marsh abutting upon the upland, (4) Fresh Marsh with 

 Stream Swamp lying between it and the upland, (5) Stream Swamp. 

 The Fresh Marshes which border the longer rivers have a rich flora 

 which is very diverse in the grouping of its species, while the Fresh 

 Marshes that lie back of the broad areas of Salt Marsh are more 

 like the Salt Marshes superficially, in the simplicity of their flora 

 and the uniformity in the grouping of the species from place to 

 place. The Fresh Marshes occupy but a small part of the course 

 of the Focomoke River, from Shelltown to Rehoboth, where they 

 give way to River Swamps. On the Nanticoke they extend from 

 Roaring Point to Riverton, and on the Choptank from Jamaica 

 Point to the confluence of Tuckahoe Creek. The water of the great 

 lagoon of Worcester County is brackish only in its lower half,* be- 

 coming fresh on passing north of Ricks Point into Newport, Sine- 

 puxent, Isle of Wight and Assowoman bays. 



*See Ducatel, Outlines of the Physical Geography of Maryland. 

 Maryland Academy Science and Literature, Vol. I., 1837, pp. 24-54. 



