100 BOTANICAL RESULTS OF THE SCOTTISH NATIONAL ANTARCTIC EXPEDITION. 



(apparently due to a species of Chlamydomonas) on the snowfields of the Carpathians. 

 Chodat, 1 lastly, also refers to black snow (neige noir), and describes a yellowish-orange 

 organism, Pteromonas nivalis, Chod., as occurring in it. All these different types of 

 snow flora, however, appear to be markedly distinct from the yellow snow collected in 

 the Antarctic, and I have therefore thought it expedient to deal with this part of the 

 South Orkney material separately. 



The organisms composing the yellow snow flora are in part similar to or identical 

 with some of those found in red and other coloured snow, but there are a number of very 

 distinct types (e.g. Protoderma broivnii, Chlorosplieera antarctica, Scotiella antarc- 

 tica, and Chodatella breiiispina) that give this association a characteristic stamp. 

 There seems some probability that the yellow snow flora is an example of what I have 

 called an algal consortium, 2 in which certain members (Protoderma broivnii) first 

 prepare a suitable substratum for the growth of the others ; but this could of course 

 only be definitely settled by observations made on the spot. All the typical and 

 common members of the yellow snow flora include a varying (but often very large) 

 quantity of an apparently solid fat in their cell-contents, which appears in the form 

 of large, highly refractive lumps. 3 The amount of this fat is often so considerable that 

 little can be seen of the remaining cell-contents, while in other cases, and often quite 

 inexplicably, the fat is completely absent. It appears that the yellow pigment, which 

 is the cause of the characteristic colour of the yellow snow, is included in this fat, 

 although, as most of the pigment had been dissolved out by the preserving fluid, I 

 cannot be certain with reference to this point. I have been unable to make out the 

 nature of the pigment, owing to the small quantity that was available ; a spectroscopic 

 examination of the alcohol in which the one sample was preserved disclosed a marked 

 absorption of the violet end of the spectrum, which would indicate that the pigment 

 might be analogous to carotin or xanthophyll, but none of the other reactions character- 

 istic of this substance were obtained. As regards the fat, neither in its general 

 appearance under the microscope, nor in its behaviour towards the various reagents 

 used (cf. footnote 3 below), was there anything to indicate a difference between the 



1 R. Cliodat, Algues vcrtes de la Suisse, Berne, 1902, pp. 96 and 145-146. See also Brim, "Sur la neige noir," Echo 

 des Aipes, 1875, p. 182. 



2 F. E. Fritsch, " Problems in Aquatic Biology," New Phytologist, vol. v., 1906, pp. 157-158. 



3 These lumps gave all the characteristic fat- reactions (cf. Zimmermann, Die botan. Mikrotechnik, Tubingen, 1892, 

 pp. 68-71). Material treated with osmic acid acquires a very characteristic appearance ; there is so much fat in the 

 different forms that the whole mass becomes Mack to the naked eye, while material thus treated and mounted on a 

 slide presents the appearance of numerous black dots when held up to the light. Under the microscope many of the 

 cells appear stained a homogeneous black, while parts of other cells are quite uncoloured owing to restriction of the 

 fat to one or two points in the cell-contents. Material of yellow snow, treated respectively with alcohol and ether 

 for two and a half days, was scarcely affected by the alcohol, although much of the fat was dissolved out by the ether. 

 Even material which had been left in absolute alcohol for over three months failed to show any marked reduction 

 in the amount of fat, so that the fat is one which is insoluble in alcohol. In the case of the material placed in ether, 

 a macroscopic change was visible after a few hours ; the algal mass no longer formed a sediment at the base of the 

 tube as at first, but was separated from the base by a clear space, consisting of ether in which large numbers of roundish 

 fat-globules could be seen floating about under the microscope. The actual cells were very much poorer in fat, 

 although by no means all of the latter could be removed except by very prolonged treatment with ether. The fat 



