FRESHWATER ALGyE OF THE SOUTH ORKNEYS. 99 



B. YELLOW SNOW (</! Plates I. and II.). 



Three samples of this peculiar type of snow flora were included in the material from 

 the South Orkneys; Nos. 1 and 3 were collected on the same date, February 7, 1904, 

 and agreed almost completely with one another ; while No. 2, which was collected 

 about a year earlier, March 27, 1903, was relatively poor in algal forms (perhaps owing 

 to its being the end of the Antarctic summer), consisting largely of hairs and other 

 foreign particles. Apart from this, however, such forms as were present were the same 

 as those found in the other two samples. All three samples came from the same 

 locality. 



Samples 1 and 3 contained a very considerable quantity of algal material, and 

 show that the yellow snow flora, when well developed, must form extensive masses. 

 In reply to inquiries, Dr R. N. Rudmose Brown has very kindly furnished me with the 

 following particulars. I quote from his letters : " Both red and yellow snow are rare 

 at the South Orkneys, and many apparent cases of the latter which I examined were 

 due only to penguin manure. The samples I sent you were taken towards the end of 

 the summer on a snow-covered plain called The Beach, that was certainly often frequented 

 by penguins, but did not contain a rookery. The samples were gathered on the surface 

 of snow that had fallen some little time past, perhaps two or three days, and whose 

 surface had been slightly melted by the sun. I do not remember ever seeing any 

 coloured snow in winter, but at that season snow was falling so continuously and 

 drifting so incessantly that any growth would be immediately covered over. October 

 to February is the warmest season, but the mean temperature even then is not above 

 32 F. . . . The colour of the yellow snow is fairly bright. I do not remember any 

 brown snow, nor have I any record of a green patch being mixed with a yellow one. 

 The algae were on the surface and perhaps two or three or even four millimetres down 

 mixed with the snow, but in sufficient abundance to give an unmistakable pale 

 (bright yellow) patch. Yellow and red snow were quite distinct from one another ; 

 they may in places have been within thirty or fifty yards of one another, but this was 

 not habitual, and I do not remember a single case of the two adjoining one another." 



A considerable number of papers have been published dealing with the type of 

 algal flora known as red snow, 1 which has been recorded from Alpine (temperate and 

 tropical), Arctic, and Antarctic localities. Brown and green snow have also been described 

 both from Alpine and Arctic regions, 2 while Rostafiuski 3 has recorded yellow snow 



1 See section C of this paper ; also J. Roy, " The Flora and Fauna of Snow and Ice," Scottish Naturalist, viii., 1885-86, 

 pp. 122-127. 



- V. B. Wittrock, "Om subns och isens flora," in Nordenskibld's Studier och Forskningar foranledda at rnina resor 

 i hiiya norden, Stockholm, 1883, pp. 65-115. See also V. B. Wittrock, "Die Flora des Schnees und des Eises 

 besonders in den arktischen Gegenden," Bot. Centralbl., xiv., 1883, p. 159 ; E. Wanning, (Ecology of Plants (Eng. trans, 

 by P. Groom), Oxford, 1909, p. 163. 



3 J. Rostafinski, "Vorlaiifige Mitk-ihmg iiber rothen und gelben Sclmee und eine neue in der Tatra eutdeckte 

 Gruppe von braungefarbten Algen " (Polish), Sitzungsber. d. Krak. Akad. d. Wissensch. (mat.-nat. sect.), 1880 ; Abstract 

 in Bot. Centralbl., viii., 1881, p. 235, and Just's Botan. Jahresber., 8 (1880), i., 1883, p. 564. 



