98 THE RELATION OF PLANTS TO TIDE-LEVELS 
higher individuals of this species are not, like those of the rockweed, dwarfed 
and sterile, but they bear tetraspores nearly as large as those growing lower 
down. 
Hildenbrandia prototypus, the wide vertical range of which has already been 
suggested, may push up to the %-foot level on the shaded rocks of the wharves 
and on pebbles in the fresh-water streams about the harbor. It may be recalled 
here that this species does not push up the streams above the limit mentioned, 
which is the highest level at which they would be surrounded by salt water 
during more than two-thirds of the high tides of each fortnight. 
5. THE SUPRA-LITTORAL BELT, FROM 8 TO 12 FEET. 
The borders of the Inner Harbor, between the 8 and 12 foot levels, differ 
greatly on different sides of it. On the north side there is a rather steep gravelly 
beach between the 8 and 10 foot levels, then a gentler, more irregular slope 
culminating in the flattened top of the Spit, at levels between 11 and 12 feet. 
On the east and west sides the natural portions of the shore in this belt are steep, 
or very steep, and in most places are well watered by springs or rivulets, so that 
typical seashore plants are seldom found above 9 or 9.5 feet. The steeper supra- 
littoral shores on these three sides of the harbor will be designated as the 
supra-littoral beach, or storm beach. 
The supra-littoral levels of the shore on the fourth, or south, side of the 
harbor form a continuation of the nearly flat Marsh, which we have seen reaches 
upward from the 1.5-foot level to about the 10-foot level, at the road forming 
the southern border of our area. This marshy portion of the supra-littoral 
shore has somewhat brackish soil-water and a different type of vegetation from 
that on the other sides of the harbor. It will therefore be distinguished as 
the supra-littoral marsh and will be separately considered. 
A. THE SUPRA-LITTORAL BEACH, OR STORM BEACH. 
This storm beach, which we are now to discuss, includes the usually steep, 
natural shores of the east and west sides of the harbor, for 1.5 or 2 feet above 
mean high water, and the south shore of the Spit from mean high-water level 
up to 12 feet. 
This belt evidently corresponds in part to the zone of “halophilous sper- 
mophytic herbs” of Warming (1909, p. 225). But the zone so called by this 
author includes also other types of plants (e. g., Salicornia and Sueda), which 
at Cold Spring Harbor are distinctly characteristic of a lower belt, and occur 
in the present one only as stragglers near its lower boundary. The present belt 
also corresponds approximately with the “ middle beach ” of Cowles (1899, p. 
115), but not entirely, since our belt includes much of the beach below the 
summer storm-line. It is, moreover, quite different as regards the character 
of its plant covering, in consequence, evidently, of the more protected position 
of the shores of the small harbor we are discussing. 
That this belt or zone is a natural one for the north shore of this harbor, with 
limits always close to the levels given, will be evident as we proceed. Because 
of the very general presence of trickling or seeping fresh water, and of the 
shade of overhanging bushes and trees, the natural shores of the west side and 
the southeast corner of the harbor, between 8 and 12 feet, differ decidedly in 
character from that of the north side of the harbor along the Sandspit. In fact, 
