XXIV. 

 ON THE OCCURREXCE OF RED SNOW IN HERTFORDSHIRE. 

 By R. B. Croft, E.N., T.L.S., F.R.M.S., Hon. Sec. 

 Eead at Ware, 22nd February, 1881. 



On the return of Captain Ross's expedition from the Arctic 

 regions in 1819, red snow, which had been found extending 

 over a range of cliffs on the shore of Baffin's Bay, in some cases 

 12 feet deep, was in its melted state subjected to careful examina- 

 tion, and was pronounced by the eminent botanist, Robert Brown, 

 to contain a unicellular plant of the order Algse, an opinion since 

 confirmed by Greville and others, and now generally adopted, the 

 plant being known by several names, amongst which that of 

 Frotococcus nivalis, given to it by Agardh, and Palmella nivalis 

 given to it by Sir William Hooker, are most usually accepted. 

 The following is a description by the authors of the ' Micrographic 

 Dictionary ' of the organism in red snow brought home by Captain 

 Parry, R.X. : — " Frond, an indefinite gelatinous mass, densely filled 

 with spherical cells, about 1-1 200th part of an inch in diameter; 

 cells with a distinct membrane, their contents consisting of 

 numerous tolerably equal granules, red or green. Between the 

 large cells lie patches of minute red granules, apparently dis- 

 charged from the large cells. Bauer and Greville both describe 

 this as the mode of propagation of the plant ; but it is probable 

 that the cells also increase by division when actively vegetating." 



In a very pleasant little book called ' Footprints from the Page 

 of Nature' I find the following: "If we place a portion of the 

 snow coloured with this plant upon a piece of white paper and 

 allow it to melt and evaporate, we find a residuum of granules 

 just sufficient to give a faint crimson tinge to the paper. Placed 

 under the microscope, these granules resolve themselves into sphe- 

 rical purple cells, from the 1,000th to the 3,000th part of an inch 

 in diameter; each of these cells has an opening surrounded by 

 serrated or indented lines, whose smallest diameter measures only 

 the 1-5, 000th part of an inch." 



The same author says, further on: "The actinic power of the 

 solar light, aided by some peculiar, and as yet unknown property 

 belonging to the natural whiteness of the suow itself, is highly 

 essential in the production of the beautiful crimson or rose colour 

 by which the red snow is distinguished ; but this colour gradually 

 changes to green when secluded from the direct action of light 

 and developed on dark or opaque objects." 



Although the above is, as I have said, the generally accepted 

 theory of red snow, yet examinations of red snow made near 

 Grimsel, in Switzerland, in 1839, at the Glacier of Aar, in 1840, 



