110 THE RELATION OF PLANTS TO TIDE-LEVELS 
Rosa carolina is scattered in wet soil near the 9-foot level, e. g., 1,270 north 
and 1,750 north. 
Rumecz obtusifolias occurs occasionally near the 9-foot level, as at 1,230 north. 
Sambucus canadensis is not infrequent near the 9-foot level, but two vigorous 
specimens 8 feet high are growing at the 8.5-foot level at 1,000 north and 1,375 
north. 
Solanum dulcamara is about as common here as on the eastern shore, and is 
always found in saturated soil, e. g., 1,030 north at 8.25 feet, and 1,260 north at 
8.25 feet, rooted in the bed of a rivulet. 
Tilia americana is growing vigorously near 1,760 north at the 9-foot level. 
Vitis labrusca is the last of these non-halophytic plants to be mentioned. 
A large Concord grape which grows on moist soil near 1,670 north, at the 8.75- 
foot level, fruits abundantly. 
The interesting feature of the occurrence of these various plants at the 
levels mentioned, on most of the west shore, as on the wet and shady parts of the 
east shore, is the fact that the soil in which they are rooted is often covered by 
salt water. It may be thus submerged for 3 or 4 hours daily even during the 
growing season. It is evident that the abundance of fresh water in the soil not 
only prevents most of the xerophytic storm-beach species from becoming estab- 
lished on these wetter shores, but this fresh water in the soil prevents the salt 
water from really penetrating it. This soil, saturated with fresh water, aided 
probably by the shade, enables the inland forms to hold the soil against the 
storm-beach species that dominate these same levels on the Spit. 
In summary, the vegetation of the east and west shores from the Spartina 
glabra belt upward to the 10-foot level is made up of a few types that withstand 
very salt water about both root and shoot, but can not endure fresh water in the 
soil, e. g., Atriplex, Spergularia, and Solidago. Other forms, such as Scirpus 
americanus, withstand fresh water in the soil and a submergence of their shoots 
in salt water for 3 or 4 hours each tide, but can not withstand shade nor the 
competition of the inland species. Finally, there are the upland and fresh 
swamp species, which will not endure salt water about their roots. These grow 
in soils saturated with fresh water, at levels where this soil and the bases at 
least of their shoots may be submerged in salt water for only brief periods (1 to 
2 hours per tide), during the growing season. 
B. THE SUPRA-LITTORAL BELT OF THE MARSH, OR BRACKISH MARSH 
(FROM 8 TO 10 FEET). 
Since detailed studies and maps have been made of the vegetation of the 
Marsh (plates x1, xx1, and xxII), we may here be content with pointing out 
the important contrasts between the plant covering of this level of the Marsh 
with that of the other shores of the harbor, especially with that of the Spit. 
A striking feature of the higher levels of the Marsh, at the south end of the 
harbor, is the absence of the most characteristic plants of these same levels on 
the Spit, with the exception of Solidago sempervirens and an occasional plant 
of Atriplex patula. Plants such as Ammophila, Cakile, Euphorbia polygom- 
folia, Lathyrus maritima, and Salsola are entirely absent from the Marsh. In 
place of these species, characteristic of the gravelly beach of the Spit, we find on 
the flat, undrained peat of the Marsh a very different set of plants. Here there 
are extensive stands of Juncus Gerardi, Spartina patens, or Distichlhs, running 
up to the 8.5 or 9 foot level, there to be mingled with, or suddenly displaced by, 
