38 THE RELATION OF PLANTS TO TIDE-LEVELS 
1. THE SPARTINA GLABRA ASSOCIATION. 
In discussing the character and distribution of this association it will be 
best, because of the differences in their nature, to take up the north shore 
separately from the east, west, and south shores. Nowhere else about the 
harbor does the Spartina association assume such prominence as along the south 
side of the Spit, which stretches across the north end of the Inner Harbor. 
We may therefore legitimately regard this as the highest development of the 
Spartina association and discuss in this connection not merely the distribution 
of the Spartina in this particular area, but also the general vegetative and 
reproductive characters always shown by this grass wherever found. The area 
occupied by Spartina on the Spit is greater than the sum of all the other 
Spartina areas of the harbor. 
Starting at the northwest corner of the harbor, we find that there is a pocket 
in the shore about 200 feet in diameter quite filled with Spartina, except for a 
few tide-pools and a fresh-water stream from a ram. From this region east- 
ward to 200 east the border of Spartina is 50 to 100 feet wide (plate vir 4). 
It then suddenly broadens out until, from 500 to 900 east, the Spartina stretches 
out 600 or 800 feet southward from the shore of the Spit proper (plate 1). This 
broad band of 8. glabra along the eastern third of the Spit serves, we shall see, as 
a protecting barrier of great importance to the plants of the upper levels of the 
beach, above 6.5 feet. 
From 800 west to 200 east the lowermost stands of Spartina are on bottom at 
from 2 feet to 2.5 or 3 feet above mean low water. Eastward from here the 
lowest or southernmost boundary of the Spartina corresponds pretty closely with 
the 1.5-foot tide-line or contour, as it does elsewhere about the harbor (see 
plate 1). It is noteworthy that though the lower border of this marsh is very 
irregular as far as 600 east, from there eastward and northward it is quite 
regular. This latter fact is probably related in some way to the presence of the 
‘strong tidal-currents through the Inlet. We shall have occasion to recur to 
this later. The level of the soil bearing most of the Spartina for 30 or 40 feet 
inward from this southern margin of the Marsh lies between the 2 and 3 foot 
levels. The upper limit of Spartina throughout this band is near the 6.5-foot 
level (plate x). Only in a few places does it fall to, or slightly below, the 6-foot 
level, as on hard gravel or on shifting sandy bottom at 2,800 north by 900 east. 
In the northwest corner of the harbor, 900 to 1,000 west, rather thickly scattered 
Spartina may grow as high up as the 7.5-foot tide-line, though the dense, pure 
stand ends here as elsewhere at about 6.5 feet. The cause for a local rise in 
the upper limit at this point is perhaps to be found in the extreme flatness of 
the shore here, which causes poor drainage, such as we shall find on the marsh at 
the south end of the harbor. Possibly the wet soil here is due to the presence of 
fresh water in the subsoil, though no adequate evidence of this has been found. 
We do not find here Scirpus americanus or S. robustus, which are commonly 
found in soil containing fresh water at these levels. 
The substratum upon which most of the Spartina glabra of this south shore 
of the Spit is growing is a more or less firm, peat-like muck. At the eastern end 
of the Spit, at both upper and lower limits, Spartina is found on a sandy 
bottom. The muck referred to may, at the upper end of the Spartina belt, be 
but a few centimeters in depth, while at the middle or lower portion of this 
belt there may be 0.5 meter or more of this muck, overlying the hard sand 
