Chapter III. CHARACTERISTIC ALGAL ASSOCIATIONS AND FORMATIONS AT 

 WOODS HOLE AND IN BUZZARDS BAY AND VINEYARD SOUND. 



As stated in the preceding pages, the life habits and distribution of marine algae 

 are affected by a number of factors, the most important of which are temperature, 

 light, depth, character of the bottom, and salinity of the water. Some or all of these 

 factors, and in special caJses others as well, determine, as a rule, the habitats and sea- 

 sons of the different species. As a result, various algae are frequently found to be 

 characteristic of particular situations, where they constitute groups or formations 

 of species. 



J. G. Agardh (1836) was the first to describe regions of algal vegetation, recog- 

 nizing on the Scandinavian coasts the presence of a zone characterized by green algae 

 (Regnum Algarum Zoospermarum), a zone of brown algae (Regnum Algarum Oliva- 

 cearum), and a zone of red algae (Regnum Algarum Floridearum). Other authors have 

 attempted similar, but more elaborate, divisions of the algal flora into regions and 

 zones, but none have been very satisfactory for the reason that the brown and red 

 algae have species which range far outside the depth or zone which is in general most 

 characteristic of their class. 



It later became apparent that the algae must be split into smaller assemblages 

 than the zones of green, brown, and red algae, and Kjellman (1877 and 1878), also in 

 studies on the Scandinavian coast, developed such a classification in detail, applying 

 the name "formation" to each group and usually naming each formation after the alga 

 most characteristic of it. Kjellman's paper of 1878, "Ueber Algenregionen und 

 Algenformationen im ostlichen Skager Rack," stands, as far as the author is aware, 

 as the first algological contribution introducing the methods and terminology of 

 ecology as at present practiced. Later authors have followed the methods of Kjell- 

 man to a greater or less degree, and among them one of the most elaborate studies 

 has been that of Borgesen (1905), "The Algae Vegetation of the Faeroese Coasts." 

 The reader will find in these two papers of Kjellman and Borgesen historical treat- 

 ments of the literature, which need not be repeated here, especially since they deal 

 with conditions in northern waters, which are very different from those at Woods 

 Hole. 



Kjellman (1877) employed the terms "littoral," a "sublittoral," and "elittoral" to 

 define three regions of distribution, and these terms are in wide use among botanists 

 and, with certain modifications of his definitions, they have replaced earlier expres- 

 sions designating regions occupied by the green, the brown, and the red algae. Kjell- 

 man defined the littoral region as that between lowest and highest tide marks, the 

 sublittoral region as that from the lowest tide mark to the furthest depth at which 

 algae will grow (about 20 fathoms on the Scandinavian coast), and the elittoral region 

 as that bottom below the sublittoral. 



" Cf. discussion on pages 178-180, section 1, of present report. 



