SPARTINA GLABRA ASSOCIATION 41 
rhizomes of the reed-grass do not rather quickly occupy these areas, which 
might then soon be built up by the deposit of the silt brought in abundantly by 
the tide. The only plausible explanation of the persistent absence of Spartina 
below the 1.5-foot level is that the conditions encountered by the rhizomes or 
shoots at these lower levels are unendurable. Just what the ultimate injurious 
factors in these conditions may be we shall suggest later, in our general discus- 
sion of the factors affecting the whole distribution of Spartina glabra. 
Practically the whole of the area south of the Spit, shown within the finely 
zigzag line on the chart, and up to just beyond the 6-foot contour, is covered 
continuously and year after year with Spartina glabra. The only considerable 
tide-pools and larger notches of bare mud along the margin are shown on our 
map. Moreover, aside from the relatively inconspicuous alge matted about 
the stalks of the Spartina, where it is less dense in growth, no other plants 
participate with Spartina in occupying the soil. Absolutely no other established 
seed plants are found in this area until we reach the 6-foot level, where we 
begin to encounter inwandering angiosperms from the next higher belt of 
vegetation. A description of the species competing with Spartina at its upper 
limit, and also of the local distribution of Spartina itself at these higher 
levels, may be left until we take up the discussion of the next higher belt of 
vegetation. 
On the east side of the harbor, because of the wharves, we find only one rather 
short strip of well-developed Spartina association. This one piece of natural 
shore on the east side extends from 100 south to 500 north, and the Spartina 
association is developed in a very interesting way here, evidently because of the 
presence of an abundance of fresh water along this shore. North of the mill, 
from 600 to 800 north, between 975 and 1,175 north, near 1,400 north, 1,650 
north, 2,150 north, and 2,400 north, there are found strips of Spartina from 
1 to 10 meters in width growing at 2 to 4 feet above mean low water, along the 
base of the wall of the wharves. These strips are covered by typical Spartina 
alone, except for the alge usually associated with it, and will therefore not be 
- considered further. 
The Spartina belt between 200 north and 500 north forms a nearly con- 
tinuous fringe, 10 to 30 meters wide, occupying the eastern shore between the 
1.5 and 6.5 foot levels, though these limits vary slightly. From 200 north to 
100 south the fringe of Spartina is only 10 to 15 meters wide, and is broken 
through at half a dozen points by fresh-water rivulets. The stand of Spartina 
shows much the same density and other characters here as on the Spit. The 
extreme lower plants, from 200 north to 500 north, are on soil at the 1.5-foot 
level, and are small and late in flowering. South of this the lower limit for 
this species moves upward till from 0 to 100 south the lowermost plants are 
often at 3 feet or even 4 or 4.5 feet above mean low water. The salt reed-grass 
is evidently kept up on high levels here by the high level of the neighboring 
tide-stream at low water. If, for example, at 100 south, Spartina were to 
grow at the 3-foot level, it must needs grow in the bed of the tide-stream, 
where the rhizomes would not only be submerged most of the time during low 
tide, but would also have to push through a firm gravelly soil. The eastern bank 
of the tide-stream all along here usually drops from a level that varies from 3 
to 6 feet above mean low water, downward abruptly for 1, 2, or 3 feet to the 
stream-bed, and Spartina is confined to the top of the bank, or to undermined 
