9 Marine Algae from Easter Island. 



By 

 F. BORGESEN. 

 With 50 text figures. 



When Professor SKOTTSBERG asked me to work out his collection of algae 

 from Easter Island I undertook with pleasure this task, as the isolated situa- 

 tion of this island made its algal flora of a special interest. 



The collection consisted of about 20 glasses, a few stones with crustaceous 

 algae and some dried specimens, mostly the same as contained in the glasses. 

 All the material brought home was collected at low tide between high and 

 low water mark and in one locality, Hanga Piko, on the west coast of the 

 island; sublitoral algae were only collected in tide-pools. 



As is understood from this, it is a small collection only, and as several 

 of the glasses contain the same large species, it was to be expected that the 

 number of species could not be great. 



At the examination of the glasses, however, fragments of other larger 

 species were found upon and among the larger algae, and also some smaller 

 epiphytic and endophytic species. Altogether 68 species have been listed. 

 Regarding several of these species the material is so scarce that there was 

 hardly enough for microscopic preparation, while it was quite insufficient for a 

 more detailed examination, a circumstance likely to have an influence upon the 

 exactness of the determination. 



At all events, the present incomplete list of species shows that this very 

 isolated island possesses a both rich and varied marine flora of which a more 

 thorough investigation, including the sublitoral vegetation, is highly desirable. 



If I would try to give my opinion on the more characteristic features of 

 the algal flora, judging from the present material, I might say that many of 

 the species are small creeping ones which by means of strong hapteres or 

 rhizoids are able to fasten themselves to the substratum; such species are f. i. 

 Gelidium pusillam, Ptilothamnion Pluma, Laurencia claviformis, Chondria repens, 

 Gyuinogongrus aequicrassus, Hypnea Esperi, Herposiphonia tenella, Dictyopteris 

 repens etc. I have also come across proportionally many species of crustaceous 

 algae. On the whole most of the species are small, the largest one found is 

 Sargassum spec. Many species form low tufts and have a cartilaginous 



