298 DR. Е. Е. FRITSCH ON FRESHWATER ALG.E 
Rostafinski * has recorded yellowish snow (apparently due to a species of 
Chlamydomonas) on the snow-fields of the Carpathians. Chodat f, lastly, 
also refers to black snow (neige noir) and describes a yellowish-orange 
organism, Pteromonas nivalis, as occurring in it. All these different types 
of snow Hora, however, appear to be very markedly distinet from the yellow 
snow collected in the Antaretie, and I have therefore thought it expedient 
to deal with this part of the South Orkneys material sepa rately. 
The organisms composing the yellow snow flora are in part similar to or 
‘dentical with some of those found in red and other coloured snow, but there 
are a number of very distinct types (e. g. Protoderma Brown, Chlorosphera 
antaretica, Scotiella antarctica, and Chodatella brevispina) 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 ў, 
in which certain members first prepare a suitable substratum for the growth 
of the others ; but this could, of course, only be definitely settled by observa- 
tions 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 $. The amount of this fat is often so considerable that 
little сап 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, us most of the pigment had been 
dissolved out by the preserving fluid, І cannot be certain with reference 
to this point. 1 have been unable to make out the nature of the pigment, 
Flora des Schnees und des Eises besonders in den arktischen Gegenden,” in Bot. Centralbl, 
xiv. 1883, p. 159; Warming, E., * CEcology of Plants’ (Engl. transl. by P. Groom), 1909, 
p. 163. 
ж Rostafinski, J., * Vorläufige Mitteilung über rothen und gelben Schnee und eine neue 
in der Tatra entdeckte Gruppe von braungefürbten Algen" (Polish), in Sitzungsber, d. Krak. 
Akad. d. Wissensch. mat.-nat. Sect. 1880; Abstract in Bot. Centralbl. viii. 1881, p. 225, and 
Лаке Boton. Jahresber, 8 (1880), 1. 1883, р. 564. 
+ R. Chodat, ‘Algues vertes de la Suisse, 1902, pp. 96 and 145-146; see also Drun, 
“Sur la neige noir," in * Echo des Alpes,’ 1845, p. 182. 
| Е. E. Fritsch, * Problems in Aquatic Biology," in ‘New Phytologist, vol. v. 1906, 
pp. 157-8. 
$ These lumps gave all the characteristic fat-reactions (cf. Zimmermann, * Die botan. 
Mikrotechnik, 1892, pp. 68-71). Material treated with osmic acid acquires a very charac- 
teristic appearance; there is 80 much fat in the ditferent forms that the whole mass 
becomes black to the naked eye, while material thus treated and mounted ona slide presents 
the appearance of numerous black dots when held up to the light. Under the microscope 
of the cells appear stained a homogeneous black, while parts of other cells are 
many 
to restriction of the fat to one or two points in the cell-contents. 
quite uncoloured, owing 
