BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 459 



(15) THU PHYLLITIS AND SCYTOSIPHON ASSOCIATIONS. 



Phyllitis jascia is common in the winter and spring on rocks just below low-water 

 mark and in the littoral region. Scytosiphon lomcntarius 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 Phyllitis in the littoral region. 



These two algae, 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 ASSOCI.^TION. 



Arthrodadia 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 loi) 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. 



Dcsmareslia 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 lyi 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 lofathoms (chart 233). 

 The form compares well with material and descriptions of Dictyosiphon kippuroides. 

 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 CAST.\GNEA ASSOCIATION. 



Castagnea Zosterae is common at Woods Hole in the summer, attached to Zostera 

 Castagnca virescens is occasionally found on rocks, Zostera, and larger algae below low- 

 water mark. Both species are present in the warm-water sublittoral formation (b), but 

 C. virescens is also a spring species. 



