FRESHWATER ALG^E OF THE SOUTH ORKNEYS. 



97 



one case (samples gathered on February 4, 1903, from a freshwater pond at an altitude 

 of 140 feet, between the peaks of Saddle Island, South Orkneys) were organisms (species 

 of Clilamydomonas) present, which had evidently been preserved in an actively motile 

 condition. For this reason it has seemed best to give as complete an account of the 

 material as possible, in the hope that subsequent investigations may lead to a better 

 interpretation of some of the forms observed. This has been carried out especially in 

 the case of the yellow snow flora. 



Some of the numerous resting-stages observed are referable to described species of 

 the genus Trochiscia, or at least come very close to them ; where this was the case, 

 they have been enumerated under the genus Trochiscia (see the systematic part of the 

 paper), although it was thought undesirable (except in one case) to establish new 

 species on this basis. It can hardly be doubted that some of the species of Trochiscia 

 are merely resting-stages of other algse, although where a definite course of reproduc- 

 tion has been observed we are probably dealing with independent forms. In the case 

 of the material from the South Orkneys, no evidence as to the authenticity of Trochiscia 

 forms was to be expected, since no single case of reproduction was observed ; and there 

 was no choice save to record the diverse structures noticed as species of this genus. 



On the whole it is astonishing that, considering the abundance of some of the algal 

 forms, only very few reproductive stages were found ; in some cases (e.g. the Trochiscias 

 just referred to, Chodatella brevispina) not even an indication of division of the 

 individuals was observed, although the material was collected during the milder portion 

 of the year (October to March). The mean temperature, however, even at this period 

 (as Dr R. N. Rudmose Brown informs me), is only 32 F. It seems therefore as though 

 many of these Antarctic forms reproduce only during very limited periods, when the 

 conditions are especially favourable. 



As above stated, the freshwater algal floras of Kerguelen and South Georgia, as 

 described by Reinsch (loc. cit.), have a rather different character. The following table 

 shows the relative composition of the algal floras of the two localities and of the South 

 Orkneys : 



A number of these were, however, only found in the yellow snow flora. 



VOL. III. 



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