SEED PLANTS OF UPPER LITTORAL BELT 83 
The seedlings of Salicornia europea are very numerous in the spring. In 
July each year plants of all sizes are found, from seedlings of 2 or 3 cm. up to 
mature plants. This indicates a marked difference either in time of germina- 
tion or in rate of development, for no seeds have as yet been shed even from the 
oldest plants of the season. The perennial 8. ambigua does not appear to spread 
by the rooting of its decumbent branches, and probably does so by its seeds, 
though its seedlings were not distinguished from those of S. europea. 
The vertical range of distribution of Salicornia europea is from 6.5 to 7.25 
feet, but small plants of it have been found as low as 5.5 feet (200 north 
by 1,020 east), and rarely it goes up to 7.75 feet (2,860 north by 500 east and 
100 south by 900 east). Salicornia ambigua is found only between the 6.5 and 
7 foot levels on the Spit, but may be capable of ranging much more widely where 
conditions encourage a more abundant growth. As a general conclusion from 
all observations made on these Salicornias, it may be suggested that the vertical 
distribution of these plants is determined primarily by physical conditions, of 
which the chief are the time of submergence of the shoot at its lower limit and 
the low percentage of soil-water at its upper limit. The horizontal distribution 
is directly influenced somewhat by soil characters, but is apparently determined 
ultimately, in the case of S. europea at least, by the power of its perennial 
competitors to hold their own against the seedlings of the Salicornia. Between 
the two species themselves there is evidently keen competition. 
Scirpus americanus in the upper litoral belt: This plant, which is a dark- 
green, few-leafed rush with triangular culms, about 0.5 cm. thick, and from 
0.5 to 1 meter high, is widely scattered about the harbor in this belt, except on 
the Spit (plate x11). Along most of the east and west shores where this rush 
occurs at all it is sprinkled in with Spartina glabra near the upper border of the 
latter (plate 1vB). Higher up there is still but a sprinkling among the suc- 
cessors of the Spartina, such as Spartina patens (e. g., 1,000 to 1,020 north by 
1,050 east). In still other places, though the stalks of the Scirpus may be thinly 
scattered, the soil between them may be destitute of other plants and perhaps 
covered with a layer of tide-trash beneath which this plant seems to persist more 
- readily than other species. There are but few places along the west shore where 
this Scirpus is abundant enough to dominate the upper littoral belt (e. g., 
between 640 and 800 north, 900 and 1,000 north, 1,850 and 1,900 north). Only 
on the southern end of the Marsh at the head of the harbor (350 to 500 south by 
1,000 to 1,150 east) do we find this species really dominant over any consider- 
able area (plates XV B, XIX B, and xx A). LHven here it seldom occurs in as pure 
a stand as that formed by Spartina glabra, 8. patens, or even by Sueda and the 
Salicornias on the Spit. The soil occupied chiefly by Scirpus is usually firmly 
bound by its rhizomes, which run about horizontally about 10 to 15 cm. below the 
surface. In the denser stands there are 10 to 15 culms per square decimeter. 
The soil bearing Scirpus americanus is peat or mud, chiefly between the 6 and 
8 foot levels. Sometimes, near the larger rivulets, it gets down to the 5-foot 
level on lumps of peaty mud which are surrounded by fresh water for 4 or 5 
hours at each low tide (1,250 north, on the west shore). It does not grow 
on the gravelly areas from which this peaty top-soil has been eroded by these 
streamlets. On the other hand, this rush may grow at considerably higher 
levels than the upper limit mentioned above. This is true at one or two points 
along the west shore (e. g., 1,700 north), and especially on the marshy area 
