100 THE RELATION OF PLANTS TO TIDE-LEVELS 
water mark that the waves formed in the harbor can force their way through 
the belt of salt reed-grass to the gravel beach behind it. When the water is at 
a lower level this grass serves as a complete barrier to the waves. © The strip of 
gravel beach is generally most bare, therefore, where the reed-grass belt is nar- 
rowest, and has something of a sprinkling of plants where this Spartina belt is 
wider. (See plates vand xiv.) The plants occupying this gravel strip between 
7.5 and 8.5 feet are, as we have seen above, chiefly species from the next lower 
belt, such as Spartina patens, Salicornia europea, Sueda, and Atriplex, though 
there is in some places a sparse sprinkling just below 8.5 feet of characteristic 
plants from the belt above, e. g., Solidago, Cakile, Salsola, and more rarely of 
Ammophila and Agropyron. 
The naturalness of the 8-foot line as the boundary between these two belts is 
evident from such facts as those just pointed out. Of the characteristic species 
of the upper beach between 6.5 and 8 feet six have been found at, or slightly 
above, the 8-foot level. But these were in places where conditions were 
evidently more than usually favorable, and none of the plants ascended higher 
than 8.25 or 8.5 feet except Atriplex arenarta, which is recorded once from 8.75 
feet." 
The usual upper limit of distribution of the characteristic plants of the 
upper littoral beach is at the 8-foot level. On the other hand, the normal 
lower limit for the four most characteristic plants of the Storm Beach is also 
very near the 8-foot level.’ 
The reason for giving 12 feet as the upper limit of the storm beach is that 
this is the height of the highest winter storm of which we have definite record. 
It is also the elevation of the highest part of the Spit and thus of the uppermost 
soil about the harbor bearing a vegetation that shows the direct influence of the 
marine environment. 
The typical distribution of the six species of plants from the upper beach 
which wander up into the storm beach, or rather into the gravel strip separat- 
ing it from the upper littoral beach, is illustrated by the chart of the belt 
transect of the Spit drawn by Professor Conard (plate xiv). This will be 
referred to incidentally in giving the distribution of the characteristic plants 
of the storm beach. It may be noted here in passing that of these plants from 
the upper beach, only the two grasses, Spartina patens and Distichlis spicata, 
are perennial. The other four species (Atriplex arenarw, A. patula hastata, 
Salicornia europea, and Sueda maritima) are annuals, and their exact local 
distribution in the areas possessing conditions endurable for them varies con- 
siderably from year to year. 
In view of the fact that the distribution of the plants of the Spit has been 
mapped in detail (plate v), and that Professor Conard has made a special study 
of the vegetation of two limited areas (plate xiv and fig. 2), we will only note 
the more general features of the dissemination of plants growing here. 
1 These species with their wsuwal upper limits and their extreme upper limits are as 
follows: Atriplex arenaria, 8 and 8.75 feet; Distichlis, 7.5 and 8.5 feet; Limonium, 
7.5 and 8.25 feet; Salicornia europea, 7.5 to 8.25 feet; Spartina patens, 7.75 and 8.25 
feet; Suda, 7.75 to 8.5 feet. 
?The usual lower limits and the extreme lower limits for the species are as fol- 
lows: Ammophila, 8.75 to 8 feet; Cakile, 8.5 to 8 feet; Salsola, 8.5 to 8.25 feet; 
Solidago, 8.5 to 7.75 feet. (Seedlings were found in one instance at 6.5 feet.) 
