COLLECTED IN THE SOUTH ORKNEYS. 299 
owing to the small quantity that was available; a spectroscopic examination 
ofthe 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 characteristic of this substance were obtained. Аз regards the fat, 
neither in its general appearance under the microseope nor in its behaviour 
towards the various reagents used (ecf. footnote $ on p. 298) was there 
anything to indicate a difference between the kind of fat present in the 
various members of the yellow snow flora. The occurrence of the fat and 
the associated yellow pigment is therefore a very characteristic feature of 
this algal association. 
The enormous prevalence of fat in the members of the yellow snow flora is 
probably to be regarded as an adaptation against the intense cold of the 
habitat. It has been shown that in a number of trees (birch, Conifers) 
growing in cold localities the starch is changed into fat т the autumn * ; and 
in referring to this fact Warming f remarks : “ This is probably of use, т 
that fatty oil in the form of emulsion prevents sub-cooling and increases the 
power of resistance to frost." This view is certainly much strengthened by 
the discovery of the yellow snow with its striking characteristic of fat- 
storage. А similar abundance of fat does not appear to have been recorded 
hitherto in any snow flora f. The fact that the few reproductive stages that 
were observed in the yellow snow material were generally quite deficient in 
fat also indicates that the latter possibly functions as a reserve to be utilised 
when outside conditions admit of cell-division or other methods of repro- 
duction taking place. 
Material of yellow snow, treated respectively with alcohol and ether for 24 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 macroscopie 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 also took on the typical 
red stain with tincture of alkanna. On the other hand, even prolonged treatment (36 hours) 
with equal parts of concentrated caustic potash and ammonia solutions, although it made 
the fat more transparent, failed to bring about proper saponification. 
* A. Fischer, * Beitrüge zur Physiologie der Holzgewüchse," in Pringsheim's Jahrb. xxii. 
1891; О. G. Petersen, * Stivelsen hos vore Troer under Vinterhvilen," in Danske Vid. Selsk. 
Oversigt, 1896; cf. also Schimper, * Plant-Geography ' (Engl. transl.), 1903, p. 41. 
T Warming, * Ecology of Plants’ (Engl. transl. by P. Groom), 1909, p. 28. 
і Ibid. p. 163. 
