BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 



469 



south of the cape in exposed situations where they may be expected to find conditions 

 approaching those of the north coast. The list is as follows: 



*Chaetomorpha melagonium. 

 *Laminaria digitata. 

 *Plumaria elegans. 

 Rhodomela subfusca. 



Actinococcus peltaeformis (o). 

 Gymnogongrus norvegicus (o). 

 Euthora cristata (o). 

 *Lomentaria rosea. 



*Rhodymenia palmata. 

 *Delesseria sinuosa. 

 Melobesia membranacea (o). 



Another group of species comprises those which range both north and south of Cape 

 Cod; many of them are conspicuous in the warm- water sublittoral formation (b). The 

 following are prominent: 



Chaetomorpha linum. 



Cladophora albida var. refracta. 



C. gracilis. 



C. rupestris. 



Ectocarpus confervoides. 



E. fasciculatus. 



E. siliculosus. 

 *Desmarestia aculeata. 

 *D. viridis. 



*Dictyosiphon hippuroides. 

 *Chordaria flagelliformis. 



Lcathesia difformis. 

 *Ralfsia clavata. 



Chorda filum. 

 *Laminaria Agardhii. 

 *L..Agardhii var. vittata. 

 *Ceramium rubrum. 



Polysiphonia atrorubescens (o). 

 *P. elongata. 

 *P. nigrescens. 



P. nigrescens var. fucoides (o). 



P. urceolata. 



Actinococcus subcutaneus. 

 *Ahnfeldtia plicata. 

 *Chondrus crispus. 

 *Phyllophora Brodisei. 



*Phyllophora membranifolia. 



Agardhiella tenera. 

 *Cystoclonium purpurascens. 

 *Cystoclonium purpurascens var. 

 cirrhosum. 



Grinnellia americana. 



Polyides rotundus. 



Corallina officinalis. 



Hildenbrandia prototypus. 



Lithothamnion polymorphum. 



Melobesia membranacea. 



M. pustulata. 



Finally there is a group of species which are widely distributed in the warm-water 

 sublittoral. Chief among them are — 



Cladostephus verticillatus. 

 *Antithamnion cruciatum. 



*Spermothamnion Turneri. 

 Rliodomela Rochei. 



The lists of species in the genera Cladophora and Ectocarpus are undoubtedly far 

 from complete, for studies at other seasons of the year would be expected to give many 

 additions. It must be remembered that we know nothing of this formation in the lower 

 portion of Buzzards Bay and the westerly portion of Vineyard Sound in the winter and 

 spring when the conditions are much more favorable for the support of a cool-water 

 sublittoral flora. 



The chief factor which determines the cool-water sublittoral formation is the 

 relatively low temperature of the bottom water during the summer months. The 

 records of the temperatures off Gay Head and Cuttyhunk for the summer, as well as for 

 other seasons of the year, are presented in a table on page 450, to which the reader is 

 referred. It is probable that the lowest winter temperatures of the bottom water at 

 these points fall somewhat below 35 °, and that the highest summer temperatures are 

 close to 6o°. This represents about the yearly range of the bottom temperatures off 

 the exposed points of Gay Head and Sow and Pigs, and in general of the extreme westerly 

 portion of Vineyard Sound and the deeper water of the lower portion of Buzzards Bay. 

 The cool-water sublittoral formation may then be said to endure a maximum tempera- 

 ture of about 6o° for a short period in midsummer, but to live for most of the year at 

 temperatures considerably lower. Its most favorable temperature is perhaps close to 

 50 or below. Whether essentially the same formation is present during the winter 

 is not known, but it seems very probable. 



