68o C. SKOTTSBERG 



Dictyotaceae-Codiuui-Rliodomelaceae Ass. On hard bottom, rock, stones 

 and balls of Lithothainnia, but also on shells, and coarse calcareous sand (shell 

 fragments, etc.). One or more species of Dictyotaceae are always present, of 

 Chlorophvceae Codiuin and often also Micyodictyoii, and of Rhodophyccae several 

 Rhodomclaceae besides many accessory species of other famihes, foliaceous or 

 fruticulose. Most forms are rather small-sized; Padhia and Codiiivi fernajidc- 

 ziannm seem to be the largest. The composition is seen from Table II. Endo- 

 phytes, microepiphytes and species known from a single locality have not been 

 included. 



Lilhothauinio)! (Lithophyllum) Ass. Where the surf is violent, a more or 

 less pure cover of crustaceous Corallines can be seen to extend below low-water 

 mark. One of the species is probably L. fernandcrJanum. In deeper water the 

 crust may form the bottom synusia of the Dictyotaceac-Codiuui-Rliodouielaceae 

 Ass. Unfortunately, the species have not been determined. 



ScytosipJion lomeiitaria Ass. Observed once, colonizing a floating buoy of 

 iron, and with a lower zone of Clva linza Ass. (See above, St. lO.) 



For m a t i on s. 



In my paper on the algal communities of southern South America, etc. 

 I tried to distinguish a number of physiognomic formations, represented in the 

 cold and temperate waters of both hemispheres. The Upper littoral formation 

 of drought-resistant algae » includes in Juan Fernandez the Hydrocolens(-Hiidcn- 

 braiidia) Ass. and the Enteromorpha-Choiidriclla-Gelidiuni Ass. The » Middle- 

 lower formation of surf resistant Rhodophyccae > seems to be very feebly de- 

 veloped. Xo Iridaea, a genus of considerable importance along the opposite 

 mainland of Chile, has been found, and species of Gigarlina seem to be rare 

 and without influence on the physiognomy. The Ulva-Gratcloiipia community 

 mentioned under St. 40 a, but not sufficiently studied, occupies approximately 

 the same position as an Iridaea Ass. 



The corresponding formation on less exposed coast is, in the Subantarctic 

 region, developed as the complex community I called the Adoiocysiis-Chloro- 

 pliyceae Ass. The dominant species are middle-sized to small brown and green 

 algae. The equivalent to this seems to be the Chaetoinopha firma-SplacJuiidiuDi 

 Ass., which because of the greater variety of fairly large brown algae [Colpo- 

 uienia, Scytosiphon, Padhia fcniaiidcziaiia^ and others) a[)proaches the northern 

 Fucus formation. 



The »Surf formation of large Phaeophyceae , with the Austral-Subantarctic 

 Durvillea Ass., is wanting in Juan Fernandez, and the same is the case with 

 other formations of large brown algae. Lcssonia, DcstnarcstJa and Macrocystis^ 

 leading genera of the mainland, are all absent. Pieces of Macrocystis were 

 collected off Bahi'a Cumberland by my zoological companion. Dr. K. B.\CKSTR(")M, 

 which shows that drift from the American coast may reach the islands. 



Equally well developed along the coast of South America and around the 

 islands is the Formation of Crustaceous Corallines », where two associations can 



