BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 451 
These records of the bottom temperature between Gay Head and the ledges of Sow 
and Pigs indicate that the average range is from below 35° in the winter to about 60° 
in the summer. The bottom temperature probably does not fall to the lowest winter 
temperature of the sheltered waters of the Bay and Sound and does not rise to within 
15° of the highest summer temperatures in such situations; the total range is close to 
26°. The surface temperature between Gay Head and the ledges of Sow and Pigs is at 
times in the summer 4° to 5° higher than the bottom temperature, and in the winter 
probably somewhat lower; the total range is close to 32°. The seasonal range in Great 
Harbor, Woods Hole, is about 46°, and it must be more than 50° in the upper portions 
of Buzzards Bay. 
The causes of these very different conditions are not difficult to understand. The 
great range of temperature in the sheltered waters of the Bay and Sound is simply the 
result of summer and winter atmospheric temperatures acting on bodies of water sufii- 
ciently shallow to respond very quickly to their influences. Tables 9 and 10 (pp. 46- 
47), giving the average monthly range of the temperatures of both air and water at 
Woods Hole over a five-year period, make clear the relationship, also shown on chart 
219. Thesmall range of the temperature of the bottom water between Gay Head and 
the Sow and Pigs, together with the greater range of the surface water, shows the effect 
of proximity to the deeper cold water of the open sea, water which, as stated before, 
appears to be an extension of the cold belt north of Cape Cod. 
It is clear from the above statements of the seasonal ranges of temperature in the 
two extremes of the conditions presented within the limits of the Survey (first, the 
bottom temperatures off Gay Head and Sow and Pigs; second, the temperatures of shel- 
tered waters of the Bay and Sound) that several very different types of floras would be 
expected, and thisis the case. The uniformly cool bottom water of Gay Head and the Sow 
and Pigs (generally below 60°) admits of the development of a flora with a number of 
species characteristic of northern waters. This flora is restricted to the lower portion of 
Buzzards Bay and the westerly portion of Vineyard Sound and is distinguished by the 
presence of the following species which are never found (at least during the summer) 
in the more sheltered regions of the Bay and Sound: Chetomorpha melagonium, Lami- 
nara digitata, Plumaria elegans, Rhodomela subfusca, Actinococcus pelteformis, Gym- 
nogongrus norvegicus, Euthora cristata, Lomentaria rosea, Rhodymenia palmata, Deles- 
serta stnuosa. It would be very interesting to know whether other northerly species 
may not be present during the winter and spring and whether this cold-water flora 
extends its range during the winter into more sheltered portions of the Bay and Sound, 
but we have made no dredgings for alge off Gay Head in the winter and know nothing 
of the deep-water flora of that season. 
The seasonal extremes in the sheltered portions of Buzzards Bay and Vineyard 
Sound, as would be expected, give at least two distinct seasonal floras, (1) that of the 
winter and early spring, and (2) that of midsummer and the early autumn. Some species 
are found all the year round, but they are generally much more luxuriant at one season 
than at the other. Many of the species are limited to a season of perhaps two or three 
months and are never found at other times. It is not at present possible to discuss sat- 
isfactorily the seasonal habits of the alge at Woods Hole, for they have been very little 
studied during the winter, but such data as are known are included in the Catalogue. 
