SPARTINA GLABRA ASSOCIATION 47 
the Creek. In general we find on the concave side of each bend a steep bank 
(plate xv B), formed by the caving of the firm turf of S. glabra and 9. patens 
from the edge of the Marsh, as the soft material below is cut out by the stream. 
For example, at 100 south to 200 south on the east bank large blocks of the 
Marsh soil, 3 or 4 meters long and a meter thick, are often cracked off. These 
blocks either settle down while keeping the Spartina turf in a horizontal posi- 
tion, or become tilted over by the rapid undermining of the western side, until 
the turf stands nearly vertical. In the substratum, with the root-collar 3 feet or 
more below the present Marsh surface, stumps of Acer rubrum are found in situ. 
The top of the Marsh along this bank, from 0 to 200 south, rises to the 7-foot 
level only 2 or 3 meters back from the edge. From this level it slopes down quite 
rapidly to a level of 6 feet or somewhat less at the very margin, evidently because 
of the settling of the surface, as the soft peaty mud below it is washed away or 
squeezed out toward the stream. It is only this narrow, sloping brim that is 
occupied at all completely by Spartina glabra. The stand is often quite sparse, 
apparently because the bank caves and the soil settles more rapidly than the 
Spartina can completely occupy the new areas thus brought down to the proper 
level for it. The denser stand of Spartina here often ends quite abruptly in some 
places,. so that beyond 0.5 meter from the upper or on-shore limit of dense 
Spartina not more than half a dozen isolated plants of this grass can be found for 
5 meters along the bank. On this eastern bank, from 200 south to 500 south, 
where the bank is not being undermined, it slopes much more gradually, and the 
Spartina belt is wider. (See plate x1.) 
The western bank of the Creek, except from 350 south to 450 south, is a 
convex one. In consequence, we have an abrupt bank, with the Spartina belt 
very narrow, only in the particular region just specified, where the conditions 
are like those of the east side between 0 and 200 south. From 300 south to 
200 north the west bank is a gently sloping one with a very wide belt of Spartina. 
The stand of Spartina on this west side shows a range in density and height 
like that on the Spit and on north edge of the Marsh. It is practically contin- 
uous, except where cut through by branches of the main stream and smaller 
- side streams, or where it is temporarily killed out by flood-trash. As an example 
of the latter we may cite an area about 6 by 12 meters at 430 south by 720 east 
which was covered by flood-trash during spring and summer in 1911. In 
September 1911 not a green shoot of Spartina could be seen on this area, 
though elsewhere this grass was still fresh and green. These areas, when the 
trash is floated off again, become covered first with alge, as we shall soon see, 
and only gradually are they reconquered by Spartina, through the growing 
inward of rhizomes from the Spartina plants round about.* 
The upper margin of the Spartina belt here at the head of the harbor lies 
between the 6 and 7 foot levels. The map shows that the margin is generally 
quite regular, except for the tongue pushing upward along each stream. A 
sudden ending of the dense stand occurs rather frequently at the upper margin 
of its belt along the north shore of the Marsh (700 to 1,000 east). In some 
places on this shore the bottom rises rather abruptly from the 6-foot to the 
4In the summer of 1913 a patch of S. glabra 40 square feet in area (at 200 north 
by 1,000 east) was smothered out by masses of Ulva. When the latter was washed off 
by storm tides the dead leaves and culms of the grass were se felted over by 
Lyngbyas, Oscillatorias and Microcoleus. 
