118 BOTANICAL RESULTS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 



The remaining algae found in the yellow snow are very rare. These include forms 

 like Pleurococcus vulgaris, Menegh., Mesotsenium endlicherianum, Naeg., Chlamy- 

 domonas caudata, Wille, Nostoc minutissimum, Kiitz., and probably other species of 

 Chlamydomonas. Lastly, mention must be made of large round cells with a smooth 

 and fairly thick membrane, and filled with yellowish -red or reddish, homogeneous or 

 somewhat granular contents (text fig. 1, D, p. 122) ; the contents were commonly slightly 

 contracted away from the wall on one side of the cell. These cells are of large size 

 (diam. = about 40-60 M) often as big as or bigger than the largest Chlorosph&ra-cells 

 and although rare are very easily recognised when present, owing to their distinctive 

 colour. These cells rather recall some figured by Wittrock, 1 and referred by him to 

 Chlamydomonas (Sphserella) nivalis (Sommerf.), Wille, but owing to their large size 

 (about 52 M) it may be doubted whether they really belong to this species. Except 

 for their larger size, there is also some resemblance to the resting - cells of 

 C. sanguinea, Lagerh. 2 



In sample No. 2 a fungus was frequently to be found which, judging by its goni- 

 diophore, was a species of Penicillium. A second fungus occurred in the other two 

 samples, but could not be determined. 8 



In concluding this consideration of the yellow snow flora, attention may be drawn 

 to one or two general features. The flora is practically entirely composed of green 

 algae (except for the above-mentioned species of Nostoc). Diatoms are represented 

 only by fragments of frustules, and there are very few even of these. The plankton 

 character of the whole flora is also a point of interest, and indicates that it may have 

 arisen in part by spores of plankton-forms being carried by the wind on to the surface 

 of the snow. This probably applies to all snow floras. 



C. RED SNOW. 4 



The three samples (Nos. 4-6) of red snow included in the collections from the 

 South Orkneys were all of them very poor in algal forms, showing that red snow in 



1 V. B. Wittrock, " Om snons och isens Flora, etc.," in A. E. Nordenskiold, Studier och forskningar, etc., Stockholm, 

 1883, pi. iii., fig. 2. 



2 Lagerheim, loc. tit., pi. xxviii., fig. 1. It having been suggested to me that the cells above described might be cysts 

 of rotifers, I sent some material of yellow snow to Mr James Murray, who very kindly informs me that the cells in 

 question are quite unknown to him and nol rotifers. On the same authority I am able to state that the yellow snow 

 includes yellow cysts (100-1 50 /) of bdelloid rotifers and a species of Collembola. 



3 Tufts of short threads, richly branched in an arborescent manner and composed of spindle-shaped cells, 1 ^ or less 

 in diameter. Cells thickest at a point about two-thirds of their length from the base ; from this point they taper 

 gradually towards the base and rapidly towards the apex of each cell. 



* So many accounts of red snow have already been published, that a general consideration seemed unnecessary, and 

 the following account deals solely with the components of the samples of red snow from the South Orkneys. The 

 most important contributions on the subject of red snow are : V. B. Wittrock, " Om snbns och isens Flora, etc.," in 

 Nordenskibld, Studier och forskningar, Stockholm, 1883, pp. 65-123, and pi. iii. ; Lagerheim, "Bidrag till kannedomen 

 om snofloran i Lulea Lappmark," Bot. Notiser, 1883 ; Lagerheim, "Die Schneeflora des Pichincha," Her. Deutsch. Bot. 

 Get., x., 1892, pp. 517-534, pi. xxviii. ; Lagerheim, "Bin Beitrag zur Schneeflora Spitzbergens," Nuova Notarisia, 

 1894 ; Chodat, "Flore des neiges du col des Ecandies," Bull. Herbier Boitiier, iv., 1896, p. 881 et seq. and pi. ix. ; 

 Chodat, Alguet verta de la Suiste, Berne, 1902, pp. 95, 96. 



