294 DR. F. E. FRITSCH ON FRESHWATER ALG.E 
and De Wildeman a number of Algæ collected by Е. Racovitza, of the 
Belgian Antarctic Expedition *. А considerable number of papers on 
Antarctic Algw deal solely with marine forms T. 
The South Orkneys (lat. about 61° 8.) are situated appreciably further south 
than either South Georgia (lat. about 55° 8.) or Kerguelen (lat. about 49* 8.). 
from which most of the previously described material has been derived. 
This may explain the marked difference in the character of the algal 
collections obtained from the South Orkneys as compared with those from the 
other two localities. In the material from the South Orkneys filamentous 
forms play a very insignificant part, and the bulk of the Alyse consists 
of unicellular and colonial species. The total number of species recorded 
from the South Orkneys in the present paper is sixty-eight (of these one 
genus and seven species are new). The table on p. 295 shows how the 
main groups are represented. "This table, however, gives no idea of the 
relative part played by the different groups. Аза matter of fact (apart from 
the abundant Prasiola), the lowly unicellular Isokonte and Cyanophyceze 
are the predominant features of the flora, the former being, on the whole, 
more abundant than the latter. In this connection we may notice, however, 
that the complete absence of common cosmopolitan forms like Scenedesmus, 
Pediastrum, Cosmarium, Closterium, ete. is very striking. The XEdogoniacez, 
as, indeed, all filamentous forms, are represented only by stray filaments. 
Only two filaments (one of Mougeotia, the other of Zygnema) of Zygnemacee 
were observed. The occurrence of filaments of the various genera never- 
theless testifies to the fact that at certain periods their development must 
be more prominent. Desmids were represented only in two samples by 
three species. Diatoms are not common, and in some samples (e. g. yellow 
snow) were almost completely absent. Their determination was in many 
ases а matter of great difficulty, аз frequently only dead fragments of the 
‘alves were to be found, and it is probable that a larger number of species 
actually oecurs than is recorded in the present paper. In a number of the 
samples the unicellular algal flora occurred as a thin covering to numerous 
muddy particles, and it was necessary to crush the latter in order to find any 
appreciable number of algal forms. 
The lowly unicellular and colonial forms of Algw are well known to be 
in many cases among the most difficult forms to determine, and to add to 
this difficulty a very large proportion of the species in the South Orkneys 
material were in the resting-stage, or at least in a sufficiently dormant 
condition to fail to show more than one phase in the life-history. This is 
ж É., de Wildeman, “Note préliminaire sur les Algues rapportées par M. É. Racovitza, 
naturaliste de l'expédition. antaretique belge," im Bull. Ac. Roy. de Belgique, 1900, 
pp. 558-569. 
+ I am indebted to Mr. & Mrs. А. Gepp and to Dr. B. р, Jackson for kind help in 
connection with the literature cited in the present paper. 
