SPARTINA GLABRA ASSOCIATION 43 
most of this shore from 350 to 500 north the Spartina is not replaced at 
its upper margin by a dense growth of Spartina patens, as it generally is 
further south, but instead by a relatively bare gravelly beach merely sprinkled 
with plants, which are, however, of considerable variety. Thus, for example, 
plants of Solidago sempervirens are encountered at 6 feet, and a few seedlings 
even at 5 feet. Salicornia europea is found from the 5-foot to the 6-foot level. 
Atriplex patula hastata occurs at 5.5 feet, out of reach of fresh water. Scirpus 
americanus follows the fresh water down to 6 feet. Triglochin maritima goes 
down to 6 feet. Plantago decipiens first appears at 6.25 feet. Scirpus nanus 
forms dense turfs on mud out of reach of flowing fresh water at the 6.25 to 6.75 
foot levels. These plants apparently are able to invade the Spartina belt 
because the presence of fresh water, either by its direct action on the roots or 
by washing away the peat from above the gravel, makes it difficult or impossible 
for the Spartina to compete with the invaders on these areas. Most of these 
competitors, it should be noted, are established on the bare gravelly areas. 
Only the Scirpus americanus and S. nanus and some plants of Salicornia and 
Plantago are found on mud, the favorite soil of the Spartina. 
The western shore of the harbor is not so completely occupied by wharves as 
is the eastern, and it therefore bears much larger strips of Spartina glabra. 
From 550 to 1,050 north the fringe of Spartina varies from 12 to 20 meters in 
width and has quite regular upper and lower borders, the former being through- 
out very close to the 6.5-foot level, and the latter running along between 
the 1.5 and 2 foot levels. From 1,220 to 2,400 north the Spartina belt is much 
more irregular in distribution, probably because of local differences in the 
amount of shade and of fresh water present along this part of the shore. 
The width of the Spartina association varies from 5 or 6 to 30 or 40 meters, as 
may be seen on the chart, and it is interrupted only by the fresh-water streamlets 
and by a small wharf at 2,200 north. The lower margin of the stand of 
Spartina runs along at or just above the 1.5-foot level as far as 2,000 north, 
but in the extreme northwest corner of the harbor retreats to the 2.5 or even 
_ to the 3-foot level. The upper margin runs near the 6.5-foot contour, but in 
a few wet or shady areas fairly dense growths of Spartina have been found at 
? or 7.5 feet, and scattered plants at even the 8-foot level. 
The stand of Spartina along the west shore, except where it extends above 
the 6.5-foot level, is pure and generally very dense. There are often 500 or 
600 stalks per square meter. The plants vary from a height of 6 to 9 dm. in 
the upper parts of the belt to a height of 18 or 20 in the middle and from 6 to 
10 or 12 near the lower margin. The largest plants seen were 23 dm. high. 
These were growing in a layer of mud 1 dm. thick, overlying a sandy subsoil at 
the 3.25-foot tide-level. On most portions of the west shore the bottom rises 
with a very sharp slope from about the 4-foot to about the 6-foot level. The 
plants of Spartina are all within a strip a few meters in horizontal width. 
Those plants growing on levels below 4 feet are rather short, being from 8 to 
10 or 12 dm. high, while those growing between 5 and 6 feet are commonly 15 
to 18 dm. high. The difference in level of bottom, combined with difference of 
size of plants, makes the Spartina appear, to one rowing along this shore when 
the tide is nearly low, as though it grew from two terraces of 3 or 4 feet 
difference in level. At half tide the outer edge of the Spartina on the upper 
terrace rises so abruptly above the water that it appears to be the outer margin 
of the whole Spartina belt. 
