MARINE ALGAL COMMUNITIES OF THE JUAN FERNANDEZ ISLANDS 677 



St. 40 b. Masafuera, Oiicbratia dc las Casas. 28.8. 1908. 



Codiuni fey>ia)idezia}ii(i)i, '''C. loiilatcrale. — ColpoJiioiia si)iuosa, Dictyoia 

 plilyctaoiodcs. Padiiia JirJiafideziamx. — ■ LaHnuc/ir clarata, '■P/oaii//iiii>/ pacificuiii. 

 '''Ptcrosiphotiia disiiclia (on Laiiroicia). 



Associations and formations. 



Littoral associations. 



MainK- hard bottom associations are represented, and all the coast must be 

 classified as exposed. Between boulders and rocks protected patches of coarse 

 sand occur, dry during low tide or tbrming shallow pools, as well as deeper 

 rock pools, as a rule with some sand or stones. Above I have tried to explain 

 why my field survey was limited to a small number of localities. The diffi- 

 culties involved apply particularly to the littoral region and the upper part of 

 the sublittoral. With regard to the former, my observations in Masatierra give, 

 I think, a fairl\- correct idea of the communities. The observations in Masafuera 

 are, however, very fragmentary. As seen from Dr. Levring's paper, very few 

 algae, which are not in my collections, are known from Juan P^ernandez, and of 

 these only one species, Gymnogo7igriis fnrcellntus. is supposed to inhabit the 

 intertidal region. Some species have been found a single time, for instance 

 PorpJiyra tiuihilicalis\ it is noteworthy that this genus seems to play a very 

 insignificant role. 



HydrocoUus lyjigbyaceus Ass. \'ery characteristic of the uppermost zone 

 in Bahia del Padre, and most likely not confined to that place. Hydrocolcus 

 forms small, gelatinous, blue-green patches of a very dark, almost black colour. 

 Associated with this is Hildenbvajidia prototypus, which is much less common. 



Calothrix vivipara Ass. F"ound once in very shallow supralittoral pools, 

 heated by the sun and not regularly reached by the spray. 



EnteromorpJia-CJiondriella-Gelidiuui Ass. The dominant upper littoral com- 

 munity in ^lasatierra. Not observed by me in Masafuera, but should occur in 

 suitable localities. The leading species are Enteromorplia hitestiiialis (not always 

 conspicuous) and especially CJiondriella pusilla and Geiidiuni psei(doi}i1rica1uvi\ 

 both are small, moss-like, light brownish pink, and form a very close carpet, 

 approximately i — 1.5 cm thick. The community corresponds to the Bostrychia- 

 Catenella-CJiaetatigiuni community of south Chile and the subantarctic region. 

 its composition is shown by the lists from three stations, tabulated below. 



Table I. The Elite yotiiorpha-Chondr id la-Gelidium Ass. 



36 a 38 a 39 a (2) 



Enterp/iiorpha itifestinalis + + + 



Chondriella piisilln -f + -f- 



Gelidium psciidomtricatuni -f + + 



« pusil/um + — 



Chaetof/iorpha o'erea -f ~ 



Ulva linsa — — + 



* 7-igida -|- — ~ 



Gi gar Una Lesson ii + — '" 



Porphyra iinibilicalis -|- . — ~~ 



