226 Rhodora [DECEMBER 
The history of the Quamquisset marsh has been almost the reverse of 
this. ‘lhe fresh water flora of a Chamaecyparis bog, which was cut 
into at one end by wave erosion, was killed back for a considerable 
distance from the sea. In consequence, the deposition of peat in this 
part of the bog was practically stopped, although it was not interrupted 
further inland. Ultimately a sloping surface was established. When, 
by subsidence of the whole area, the lowest part of this slope reached 
the high tide level, Spartina patens and Juncus Gerardi occupied it. 
After further subsidence, Spartina glabra replaced these two species, 
which moved farther up the slope. In this case it will be noticed that 
the order of the two zones from the sea landward is the same as in a 
typical salt-marsh, but that the vertical arrangement of the strata is 
just the reverse. 
Under ordinary circumstances, the growth in thickness of Spartina 
patens turf is very rapid, and easily keeps pace with the lowering of a 
marsh surface by subsidence, but at Quamquisset Harbor very little 
silt is brought in by the inflowing tides and still less is derived from the 
surrounding slopes, so that the salt-marsh deposits consist of a densely 
matted mass of root stocks at most a few inches thick. In more 
typical salt-marshes the Spartina turf usually contains far more silt 
than organic matter, and is therefore less compact. 
Between the two zones of markedly halophilous plants and the fresh 
bog vegetation above high tide level occur two zones the flora of which 
consists of facultative halophytes. Among them are halophytes which 
grow as well in a non-saline as in a saline situation (e. g. T'riglochin 
maritima, Ptilimnium capillaceum, etc.) and, conversely, plants which 
are typical of our upland fields and woodland (е. g. Aspidium Thely- 
pteris, Rhus Toxicodendron). Athough these plants are subjected to 
great extremes of salinity (their varying ability to withstand which 
probably accounts for their zonation), the analytical data presented 
below show that in at least the upper of the two zones, the salinity at 
the height of the growing season is very slight indeed. In this connec- 
tion the conclusions of Kearny ! and of Olsson-Seffer ? in regard to the 
salinity of soil water on sea beaches have an important bearing. Briefly 
summarized, they are as follows: — 1) that the salinity of the soil water 
of the middle and upper beaches is in reality very slight, but, as in the 
transition zones of the salt marsh, subject to great fluctuations; 2) 
! Are Plants of Sea Beaches and Dunes true Halophytes? Bot. Gaz. xxxvii (1904), 
p. 424. 
2 Relation of Soil and Vegetation on Sandy Sea Shores. Bot. Gaz. xlvii (1909), p. 85. + 
