FRESHWATER ALG^. 3 



connection, as it shows that this group is not altogether unrepresented, although it 

 evidently plays no part in determining the character of the algal flora. It appears 

 that the group of the Conjugatse becomes gradually less abundant as the Antarctic 

 circle is entered {cf. Table on p. 6). Eeinsch's reports on the Algae of Kerguelen 

 and South Georgia* disclose quite a considerable number of representatives of the 

 group ; stray representatives were found among the Algae of the South Orkneys 

 (Fritsch, op. cit.) ; while a study of two separate sets of collections from the extreme 

 southern latitudes, from which the ' Discovery ' Algae were gathered, has been 

 necessary to disclose the presence of a single Desmid. The same statement applies 

 with less force to the filamentous Chlorophyceae. 



The prevalence of the Cyanophyceae is truly astonishing. Huge sheets of 

 Phorinidium and occasionally of Lynghya flourish in the ice, and during the milder 

 part of the year in the waters of the ponds and lakes. The so-called " fragments " of 

 these sheets, brought back in a dry condition by the Expedition, indicate the 

 luxurious growth of these forms that must prevail. These sheets serve as a 

 substratum for a rich growth of other Cyanophyceous forms [Microcystis, Chroococcus, 

 Lynghya, Oscillatoria, Nostoc, Calothrix, Anahaena, etc.), as well as for species of 

 Pleurococcus [P antarcticus W. and G. S. West, P. frigidus W. and G. S. West, 

 P. koettlitzi sp. n., P. dissectus Nageli). The composition of this epiphytic flora 

 is largely analogous or identical in the diff"erent ponds, as the lists given on p. 4 show. 

 It seems likely that these Cyanophyceous sheets are the breeding places for the bulk 

 of the algal flora. The material at my disposal consisted largely of such sheets with 

 their epiphytic vegetation, but Messrs. West were mpre fortunate in having several 

 collections containing free-floating Algae. I have encountered a number of the species 

 recorded by them from these samples as ffee-floating, leading an epiphytic life on the 

 Cyanophyceous sheets {e.g. Pleurococcus antarcticus, species of Oscillatoria, etc.). 



As regards the actual composition of the blue-green flora the bulk of the species 

 certainly belong to the Oscillarieae, but a considerable number of genera of 

 Chroococcaceae are represented, and the ' Discovery ' collections contained appreciably 

 more heterocystous forms f than those examined by Messrs. West. In short there is 

 every indication that further investigation will lead to the discovery of most, if not all, of 

 the leading Cyanophyceous genera in the extreme south. This relative abundance of the 

 group has already become evident as a result of the earlier reports on Antarctic Algae,J 

 all of which disclose a prevalence of Cyanophyceae, and it is evident that this group must 

 be named together with Prasiola as an essential characteristic of the Antarctic flora. 



There appears to be a great degree of uniformity in the freshwater Diatom-flora 

 of these regions. The common species are Naviculas (N. muticopsis Van Heurck, 



* See Phil. Trans. Eoy. Soc. London, 168 (1879), pp. 65-92; and "Die intemationale Polarforschung, 

 1882-88," Die Deutsolien Expeditionen und ihre Ergebnisse, Berlin, ii. (1890), pp. 329-365. 

 t It is interesting to note that a large number of these are new. 

 X Cf. P. F. Reinsch, op. cit. 



