V. SUMMARY AND CONCLUSIONS. 
The Inner Harbor of Cold Spring Harbor has an area of 110 acres at high 
water. At low tide it has an area of 45 acres, with a maximum depth of 7 feet 
over an area only 100 feet in diameter. The mean range of tides is 7.75 feet. 
By the aid of two series of perpendicular range-lines, marked with stakes, 
the positions of tide-lines, or of plants on the shore or in the harbor, could be 
accurately determined and recorded. A tide-curve was constructed from read- 
ings made on a tide-stake, and checked by one made later by a self-recording 
tide-gage. From this tide-curve the times of submergence and exposure of 
shore-levels, and thus of plants, were determined. 
The chief vegetational zones or belts distinguished, with their upper and 
lower tidal limits, are the following: (1) The plankton, of Diatomacez and Peri- 
dinew. (2) The bottom vegetation (—5 to +1.5 feet), including the “ enhalid 
formation ” of Ulva, Enteromorpha, Zostera, and Ruppia; the “ lithophilous 
benthos ” of Enteromorpha, Ulva, Fucus, Pylaiella, Chondrus, Porphyra, etc., 
attached to stones and shells, and the epiphytic alge on Zostera and Ulva, 
chiefly diatoms, Enteromorpha and Ceramium. (3) The mid-littoral belt (1.5 
to 6.5 feet). This is the most clearly limited belt about the harbor. It in- 
cludes a Spartina glabra association on sloping shores and a rockweed associa- 
tion, of Fucus, Ascophyllum, and Bostrychia, on the wharves. (4) The upper 
littoral belt ( 6.5 to 8 feet), which has a more varied vegetation, including asso- 
ciations of felted filamentous alge, of Spartina patens, of Salicornia, of Sueda, 
and of Scirpus, each either pure or mixed with members of one or more of the 
other associations mentioned, or with more or less scattered individuals of Scir- 
pus, Distichlis, Atriplex, Limoniwm, or Spergularta. (5) The supra-littoral 
belt (8 to 12 feet). ‘This is less clearly defined and more varied in make-up 
than the other belts. It includes associations composed of Ammophila, Solidago, 
Salsola, Cakile, and Lathyrus, of Scwrpus americanus and 8S. robustus, of 
Aspidvum thelypteris, and also includes more scattered and mixed groups of 
Asclepias, Aster, Baccharis, and Hibiscus, besides many upland plants. 
The external environmental factors which influence the distribution of plants 
in this harbor are: substratum, water-currents, changes in water-level with the 
tides, salinity, and temperature of the water. 
The substrata, aside from living plants, vary from fine silt, humus, or peat, 
to sand, gravel, rocks, and logs. The plant-covering at any level differs with 
the type of substratum, depending largely on the drainage possible. The soft, 
undrained mud of the very bottom of the harbor bears only Zostera, Ruppia, and 
anchored plants of Ulva and Enteromorpha. Other plants of the bottom, all of . 
them alge, require a firm substratum, as stone, a shell, or another plant, for 
attachment. ‘T’he physical character of the soil greatly affects the rate of 
drainage of salt water from shore between the tide-lines and of fresh water 
from the upper levels, and thus determines the type of vegetation growing on 
them. For example, where the soil of the Spit above the 6-foot level is gravelly 
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