98 H. JONSSON 



the vegetation, as I have thought it better to designate the algal 

 Benthos taken as a whole by this word, and to call it the "algal 

 region." 



I have also avoided the term "formation." The algal formations 

 established by Kjellman and others are not real formations, but 

 only associations (Warming, 72, p. 171), and the entire marine 

 algal vegetation is given as a subformation of marine algse (Halo- 

 nereid; Warming, 72, p. 169). I do not think that the term "forma- 

 tion" should be used in connection with the algal region in any 

 other sense than that in which it is used in connection with land 

 vegetation. As the term "fades" cannot be used in English to de- 

 note a vegetation-unit (Warming, 72, p. 146, foot-note) I have 

 avoided it. 



I divide the vegetation in each of the three zones into asso- 

 ciations, and where I think they are closely allied I combine them 

 into communities. 



Sometimes by the suffix "etum" is meant the subordinate part 

 of an association, and sometimes a vegetation-unit which almost 

 corresponds with an association. 



ACCOUNT OF THE MARINE ALGAL VEGETATION AND THE 

 SEA-GRASS VEGETATION. 



A. The Marine Algal Vegetation. 



a. The Littoral Zone. 



aa. The Photophilous or strictly Littoral Communities. 



1. The Prasiola stipitata-association. 



2. The Community of Filiform Algae. 



3. The Community of Fucacese. 



+ The Pelvetia-Fucus-spiralis-belt. 

 + -t- The Fucus-belt. 



4. The Enteromorpha-association. 



5. The Acrosiphonia-association. 

 bb. The Shade-vegetation. 



6. The Hildenbrandia-association. 



7. The Rhodochorton-association. 

 cc. The Vegetation of Tide-pools. 



b. The Semi-littoral Zone. 



8. The Monostroma-association. 



9. The Chorda-association. 



