A44 BULLETIN OF THE BUREAU OF FISHERIES. 
a large number of species not found at all north of Cape Cod and some that have been 
reported only in a few sheltered situations where the temperature of the summer undoubt- 
edly rises much above the average of the general region. It comprises certain species 
which are present in the north Adriatic and other parts of the Mediterranean and some 
that are found south of New Jersey, in the West Indies, and in other warmer seas. The 
generally sandy character-of the coast from New Jersey southward serves to separate 
the flora of Long Island Sound from that of Key West and the West Indies. Certain 
species that are typically northern or arctic in their habitats are found all the year round 
in some localities south of Cape Cod where the conditions are sufficiently favorable for 
their growth, and a number of other species appear in the winter season. However, 
the algal flora of the summer stands in sharp contrast to that north of Cape Cod, and 
resembles in many respects the floras of warmer seas, although a number of important 
groups, characteristic of such regions, are not represented in the flora of Long Island 
Sound. 
The reasons for the peculiarities which are noticed at once in the algal flora south 
of Cape Cod are in general quite as evident as are those for the boreal characteristics 
north of the cape. Cape Cod forms a barrier which holds the cold waters of the north | 
somewhat as in a pocket and greatly checks their mingling directly with the waters of 
Nantucket and Vineyard Sounds to the south. Nantucket and Marthas Vineyard, 
together with various shoals, form barriers which still further protect these sheltered 
sounds from the cooler water which lies off such exposed points as Gay Head and No 
Mans Land. ‘This offshore cooler water is probably an extension of the-cold belt north 
of Cape Cod, which continues southward around the cape. The proximity of the Gulf 
Stream, which lies only about 80 nautical miles off the coast of Nantucket, is also a 
factor of considerable importance. While the Gulf Stream does not send any well- 
marked side currents toward the coast, it must, nevertheless, greatly modify the tem- 
perature of the water which lies between it and the shore. It is well known that southerly 
storms bring surface water from the Gulf Stream toward the coast, for masses of gulf- 
weed, Sargassum bacciferum, with animal inhabitants characteristic of sargasso seas 
(such as the nudibranch, Scylle@a pelagica, certain crabs, Planes minutus and Portunus 
sayi, and the fish Pterophryne historio) are not infrequently found in Vineyard Sound 
and other bodies of water, especially where tidal currents are so strong as to bring them 
near to land. 
The waters south of Cape Cod, embracing such bodies as Vineyard Sound, Buzzards 
Bay, Narragansett Bay, Long Island Sound, and the regions that lie between, are then 
effectively protected from the influence of the cold water north and east of the cape, and 
consequently are able to become relatively warm during the summer months. The fact 
that these waters are generally shallow permits them to respond very quickly to the 
atmospheric changes at different seasons and makes possible great extremes during the 
year. Their temperature in the winter falls close to freezing point, but rises in the 
summer to 70° F. and above. Some of the most sheltered harbors and bays may even 
become much warmer than that during the summer, while they regularly freeze over in 
the winter. Such a wide range of temperature throughout the year permits a great 
variety in the life conditions, which is expressed by sharp seasonal changes in the char- 
acter of the flora. Itis the high temperature of the summer which at this season accounts 
for the development of the characteristic summer algal flora with its resemblance to the 
floras of southern seas. 
