8 Rhodora [JANUARY 
from what it is below. The reasons for this are as have been noted 
that the conspicuous Fucus- and Laminaria-associations of the north 
shores are, to some considerable extent, represented all along the 
rocky coasts and are more or less conspicuously situated in the literal 
or upper sublitoral belts, while to the south, these associations occur 
but seldom and scattered, and the Laminaria-associations, in parti- 
cular are well down in the sublitoral belt and consequently, seldom 
seen. 
The remaining question to be raised and, if possible, answered, is 
as to the exact relation of Cape Cod to the isotheres of 15? C. and 
20? C. and, consequently its situation as to the North Temperate 
and the North Subtropical Zones. The normal or dominant marine 
flora north of the cape is clearly that of the North Temperate, inter- 
mingled with the florae of the Lower and Upper Boreal Zones as 
seasonal invasions. 'The normal or dominant flora of the Long 
Island Sound district is just as clearly that of the North Subtropical 
Zone. If Cape Cod is not the strict dividing line, as appears certainly 
to be the case, where is that dividing line and what is its relation to 
Cape Cod? The isothere of 15° C. strikes the coast a little to the 
north of New England and its relations to the coast itself are some- 
what complicated. It is sufficient for our present purpose, however, 
to say that it 1s far north of Cape Cod. "The isothere of 20? C., on 
the other hand, is represented on the temperature charts as coming 
toward land some miles west of Montauk Point at the eastern ex- 
tremity of Long Island. "Taken literally, then, the Cape Cod penin- 
sula is situated well within the North Temperate Zone. An examina- 
tion of the charts of this portion of the New England coast, however, 
and of such temperature data as are available, show that the iso- 
there of 20? C. bends eastward in an irregular sort of a way, to include 
at least the more or less enclosed and shallow waters of the easternmost 
corner of Long Island Sound, Narragansett Bay, Buzzards Bay, 
Vineyard cr Nantucket Sound and the Nantucket Shoal up the 
neighborhood of Chatham on the outer Cape Cod peninsular (cf. Set- 
chell, 1915, p. 296). The influence of the warmed up water of these 
shallow and more or less enclosed areas is doubtless felt some ap- 
preciable distance out beyond their boundaries, but exposed points 
like those at Gay Head, outer coast of Rhode Island at Newport, 
Point Judith and Watch Hill, Block Island, and the eastern end of 
Long Island Sound at Montauk Point, vicinity of New London 
