106 THE RELATION OF PLANTS TO TIDE-LEVELS 
It is worthy of note that those species of the next lower belt, which on the 
Spit may wander up to 8 or 8.2 feet, seldom get above 7.5 feet on this part of 
the eastern shore. Only at one drier spot here (320 north) do we find a few 
plants of two of these (Atriplex patula and Iimomum carolimanum) growing at 
8.2 feet. Not only is this true, but Spartina glabra itself is forced down to the 
6-foot level on the wetter parts of this shore. The general effect of the abun- 
dance of fresh water in the soil is to push the upper limit of the mid-littoral and 
upper littoral associations downward to 6 inches below their usual levels, on the 
Spit, on the Marsh, and on the more exposed parts of the western shore. 
On the other hand, the abundance of fresh water in the soil of this east side 
allows certain upland and fresh marsh plants to push down to considerably 
lower levels than usual. Thus, e. g., we have noted (p. 87) that Iris versicolor 
is scattered along this shore, sometimes as low as 7.5 feet (at 10 north, 350 
north, 400 north, ete.). The soil about the roots of these plants is thus probably 
fresh, though the sturdy leaves and flower stalks are submerged in salt water 
daily, except during the smallest neap tides. In like manner Samolus flori- 
bundus pushes down to the 7.5-foot level, where its shoot is also regularly sub- 
merged in sea-water, but its roots remain embedded in a soil saturated with fresh 
water. These cases illustrate an advance of these species into areas below their 
usual lower limit, similar to that of Scirpus americanus on the west side, e. g., 
at 1,230 north, where this plant follows the fresh-water rivulets down far below 
its usual lower hmit of 6.5 or 6 feet. 
A considerable number of other swamp or fresh marsh plants, though not, 
like Jris, found below mean high-water level, do grow just above it, where their 
roots and parts of their shoots are covered by the higher tides during the growing 
season. Among such forms the following are of interest: Aspidium thelypteris 
occurs in several clumps at 8.7 to 9 feet (near 400 north). The tall shrubs 
Benzown estiwale and Clethra alnifolia are found on wet, springy banks at 8.5 
to 8.8 feet (e. g., 10 to 70 north); Cicuta maculata is found occasionally in 
saturated soil just above the 8-foot level (110 south) ; Hupatorium purpureum 
and Lysimachia terrestris also occur as low as 8 feet near the latter point; 
Sagittarva latifolia forma obtusa grows at the 9-foot level in an area where fresh 
water is present in the soil, though not abundant enough to run off from the 
surface (near 200 north); finally, Symplocarpus fetidus also pushes down 
below the 9-foot level (e. g., 110 south). 
The highest storm-tides observed during the session of the Laboratory, July 
1 to August 15, reached slightly above 10 feet. Night tides rising to 8.5 feet 
or more occur for several days in succession during spring tides. It will be 
interesting, while keeping in mind the height of these extreme summer-tides, to 
note the more important inland plants, besides the few marsh plants just men- 
tioned, that have been seen below the 10-foot level on this wet eastern shore. The 
following are the more important of these species, with the lowest level at which 
each has been found: Alnus incana, a number near 200 north at 9 feet, on soil 
rather dry at the surface; also dense clumps, 12 feet high, at 9-foot level, from 
50 to 100 south; Ambrosia artemisiefolia, near 350 north at 9 feet; Asclepias 
wncarnata near 100 south, at 8.2 feet, in very wet soil; at 350 north in better 
drained soil at 9 feet; Convolvulus sepium, 200 north, at 8.5 feet; Daucus 
carota, 350 north at 9 feet ; Hquisetum arvense, 400 north at 9 feet; Hupatorium 
perfoliatum, 110 to 120 south at 8.2 feet, and 350 north at 9 feet; Hypericum 
