BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 461 
Laminaria digitala was found only off Gay Head (chart 237) over sandy and stony 
bottoms in 3 to 13 fathoms, accompanied by the other forms of Laminaria. All of 
these kelps are characteristic members of the cool-water sublittoral formation (A), but 
Laminaria Agardhiw is more widely distributed than the others. 
(25) THE FUCUS AND ASCOPHYLLUM ASSOCIATIONS. 
Ascophyllum nodosum and Fucus vesiculosus are the only rockweeds that develop 
extensive associations in these waters; the other two species of Fucus do not form 
very conspicuous growths. 
Ascophyllum nodosum grows plentifully over rocks near low-water mark and above 
in somewhat sheltered situations. It is found in its best vegetative condition during 
the winter snd spring culminating with the fruiting period in May; the summer growth 
is somewhat dwarfed and much lighter in color (yellowish) where exposed to bright 
sunlight. 
Fucus vesiculosus, with its several forms and varieties, is more plentiful than A sco- 
phyllum, growing over a wide zone from below low-water mark to a high point in the 
littoral region. It is likewise found in its best vegetative condition during the winter 
and spring, fruiting most abundantly in the latter season. It is represented during 
the summer by dwarfish growths, frequently lighter in color than the winter condition, 
except off exposed points as at Gay Head, where the growth and fruiting is more uniform. 
The Ascophyllum and Fucus frequently form a mixed association at Woods Hole, 
which during the winter develops a broad zone in the littoral region over rocks that are 
not subjected to severe scraping by the ice. Most of the winter growths matures during 
the spring and the display during the summer is comparatively poor. 
(26) THE SARGASSUM ASSOCIATION. 
Sargassum Fuilipendula is common during the summer in the warmer and more 
sheltered regions of the Bay and Sound (chart 238); it was dredged over sandy, shelly, 
and stony bottoms in 214 to 15 fathoms, sometimes froming rather large beds. At 
Woods Hole there are conspicuous associations at the entrance to the Eel Pond and off 
Juniper Point, where the plants grow in large patches in 3 feet to 1 or more fathoms of 
water. Sargassum is thus strictly sublittoral, in sharp contrast to the habits of the 
species of rockweeds, and it is characteristic of the warm-water sublittoral formation (B). 
(27) THE BANGIA ASSOCIATION. 
Bangia fusco-purpurea is not uncommon, forming patches on rocks and woodwork 
of wharves near high-water mark. Ulothrix flacca is frequently mixed to a greater or 
less degree with the Bangia. 
(28) THE PORPHYRA ASSOCIATION. 
Porphyra laciniata frequently develops heavy growths on the harbor walls at Woods 
Hole near low-water mark. Porphyra leucosticta is a spring species common on larger 
alge and on Zostera. 
