FRESHWATER ALGAAS. 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 Conjugate becomes gradually less abundant as the Antarctic 
circle is entered (cf. Table on p. 6). Reinsch’s reports on the Algxe of Kerguelen 
and South Georgia * disclose quite a considerable number of representatives of the 
group; stray representatives were found among the Algw 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’ Alex were gathered, has been 
necessary to disclose the presence of a single Desmid. The same statement applies 
with less force to the filamentous Chlorophycez. 
The prevalence of the Cyanophycez is truly astonishing. Huge sheets of 
Phormidium and occasionally of Lyngbya 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 (Jicrocystis, Chroococeus, 
Lyngbya, Oscillatoria, Nostoe, Calothrix, Anabaena, ete.), as well as for species of 
Pleurococcus (P. antarcticus W. and G. 8. West, P. frigidus W. and G. S. West, 
P. koettlitzi sp. n., P. dissectus Nigeli). The composition of this epiphytic flora 
is largely analogous or identical in the different ponds, as the lists given on p. 4 show. 
Tt 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 more fortunate in having several 
collections containing free-floating Alow. I have encountered a number of the species 
recorded by them from these samples as free-floating, leading an epiphytic life on the 
Cyanophyceous sheets (e.g. Plewrococcus antarcticus, species of Oscillatoria, ete.). 
As regards the actual composition of the blue-green flora the bulk of the species 
certainly belong to the Oscillaries, but a considerable number of genera of 
Chroococcacez are represented, and the ‘ Discovery’ collections contained appreciably 
more heterocystous forms 7 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 Algz,t 
all of which disclose a prevalence of Cyanophyceve, 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. Roy. Soc. London, 168 (1879), pp. 65-92; and ‘Die internationale Polarforschung, 
1882-83,”’ Die Deutschen Expeditionen und ihre Ergebnisse, Berlin, ii. (1890), pp. 329-365. 
+ It is interesting to note that a large number of these are new. 
t Cf. P. F. Reinsch, op. cit. 
