BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 459 
(15) THE PHYLLITIS AND SCYTOSIPHON ASSOCIATIONS. 
Phyllitis fascia is common in the winter and spring on rocks just below low-water 
mark and in the littoral region. Scytosiphon lomentarius is also abundant in similar 
situations on rocks, and also on stony beaches, where it develops extensive growths 
during the winter and spring extending above the Phyllis in the littoral region. 
These two alga, so conspicuous in the littoral during the winter and spring, prac- 
tically disappear during the summer, being then found only in very favorable situations, 
as, for example, at Gay Head and at Grassy Ledge, in Woods Hole Harbor, on the 
side of the ship channel. They frequently form a mixed association, but Scytosiphon 
is the commoner of the two and more widely distributed. 
(16) THE ARTHROCLADIA ASSOCIATION. 
Arthrocladia villosa, which has been considered rather rare, was found by the Survey 
to be widely distributed in Buzzards Bay and Vineyard Sound (chart 230). Although 
generally dredged in small quantities, it was obtained in abundance in the cove west 
of Cuttyhunk Neck (near station 101) July 27, 1905. At this date large plants in full 
fruit grew on shells and stones in 4 to 5 fathoms, forming large patches over the bottom. 
The species is a member of the warm-water sublittoral formation (B). 
(17) THE DESMARESTIA ASSOCIATION. 
Desmarestia aculeata is a large coarse species plentiful in the lower portion of 
Buzzards Bay and westerly portion of Vineyard Sound (chart 231). It grows over sandy 
and stony bottoms in 1% to 14 fathoms. Although the plants are more often scattered, 
they sometimes form patches which would be considered as associations. The species 
is frequently a member of the cool-water sublittoral formation (a). 
Desmarestia viridis is found not only in the same situations as D. aculeata, but 
also in quieter and warmer regions of the Sound (chart 232). It is common at Woods 
Hole in the spring and early summer, a little below low-water mark. The growths 
are generally scattered, but they may also form dense associations. This species is a 
member of the warm-water sublittoral formation (B), but is also present in colder 
waters, although not so common there as Desmarestia aculeata. 
(18) THE DICTYOSIPHON ASSOCIATION. 
A species of Dictyosiphon is present during the summer months rather widely 
distributed in both Bay and Sound on stones and over sand in 3 to rofathoms (chart 233). 
The form compares well with material and descriptions of Dictyosiphon hippuroides. 
However, in view of the difficulties in determining species in this genus and the fact 
that our material was evidently a summer seasonal condition, we do not feel sure of 
its affinities. It was found at several stations in sufficient quantity to constitute asso- 
ciations, and is present in both the cool- and warm-water sublittoral formations. 
(19) THE CASTAGNEA ASSOCIATION. 
Castagnea Zostere is common at Woods Hole in the summer, attached to Zostera 
Castagnea virescens is occasionally found on rocks, Zostera, and larger alge below low- 
water mark. Both species are present in the warm-water sublittoral formation (B), but 
C. virescens is also a spring species. 
