BIOLOGICAL SURVEY OF WOODS HOLE AND VICINITY. 455 



tions to such factors as proximity to low-water mark, temperature, exposure to air or 

 to sunlight, sheltered and shaded stations, salinity of water, character of attachment, 

 etc. These groups of species may cover large areas and even form broad zones of 

 vegetation so clearly defined and conspicuous as to deserve the name of formations; 

 but the vegetation more often consists of small and scattered groups the limits of which 

 are generally more easily recognized and in which a single species very greatly predomi- 

 nates. These smaller units, usually recognized by the preponderance of a single spe- 

 cies, are called by Borgesen (1905, p. 707) associations, and we shall employ that term 

 in the brief account that follows. 



The regions included in the limits of the Survey do not, on the whole, afford mate- 

 rial for a very satisfactory study of algal associations and formations. There is noth- 

 ing that compares with the picturesque zonation of algae above and below low-water 

 mark, as illustrated in many localities north of Cape Cod, and such as have been so thor- 

 oughly studied by Kjellman, Rosenvinge, and others along the Scandinavian coasts 

 and in Greenland, and by Borgesen for the Faroes. The chief reasons for the compar- 

 atively undeveloped character of the formations and associations at Woods Hole and 

 vicinity are four in number: (i) The small tides give a relatively narrow strip of coast 

 line, generally only a few feet wide, available for the development of a littoral flora; 

 (2) a shore line of bowlders, frequently broken by sandy or gravelly beaches, presents 

 no smooth perpendicular or slanting surfaces where the attachment afforded to algae 

 is uniform in character; (3) the absence of a marked boreal flora, except for the rela- 

 tively few representatives that are present chiefly in the winter and early spring, deprives 

 the region of a number of species of Monostroma, Alaria, Dictyosiphon, Fucus, Laminaria, 

 Sacchoriza, Gigartiiia, and Halosaccion, which are conspicuous north of Cape Cod; and 

 (4) the scraping of the ice along the more sheltered shores effectually prevents the 

 development of a littoral flora in the winter season, which is the most favorable for 

 the growth of green and brown littoral species. 



One has only to look at the remarkable plates of Borgesen (1905) illustrating the 

 littoral algal associations and formations along the coasts of the Faroes to realize how 

 poorly developed is the littoral flora at Woods Hole. There are also no rock pools or 

 caverns harboring the striking assemblages of algae characteristic of such situations. 

 On the other hand, certain peculiarities of bottom, tidal channels, shallow harbors, and 

 coves give conditions and resulting floras that are not present in many northern seas. 



The arrangement of the associations follows in general the order of the Catalogue, 

 where will be found the records upon which these brief accounts are based. The number 

 of species discussed or listed is far short of the total list given in the Catalogue; they are 

 merely those sufQciently conspicuous to be worthy of attention in a treatment of algal 

 associations. 



For descriptive purposes Buzzards Bay has been regarded in this section of the 

 report as being divided into an upper and lower portion by a line drawn from the west 

 end of Naushon (Robinsons Hole) to Round Hill Point. Vineyard Sound has been 

 divided into three regions, (a) the westerly portion from the entrance at Gay Head to a 

 line drawn from the west end of Naushon (Robinsons Hole) to Kopeecon Point, (6) 

 the narrow portion from this line to one between Nobska Point and West Chop, and 

 (c) the easterly portion from the latter line to one drawn between Falmouth Heights 



