38 TRANSACTIONS OF THE [Sess. lxxvi. 



matter as a sediment. 1 The snow-water carries the dust 

 which gathers on lying snow, fine particles of mineral 

 matter and fragments of plants, and it also collects other 

 materials as it trickles over the surface. Snow-dust, 

 according to Ratzel, may contain 50 per cent, of organic 

 matter, and as this with the finely divided mineral matter 

 is laid down amongst remains of last year's vegetation, a 

 rich soil is built up. The soil is dark and finely fibrous 

 and when lifted adheres together as clods. On Lawers 

 this turf contains numerous particles of glittering mica, 

 while other samples from Sutherland show particles of 

 gneiss. Brockmann-Jerosch points out that this sub- 

 stratum owes its origin solely to the action of snow-water 

 and rain, and that the snow-flush vegetation occurs where 

 the snow-water collects, not necessarily where the snow- 

 patches lie longest. The substratum results, therefore, 

 from slow sedimentation combined with growth of vegeta- 

 tion which is not swept away but remains perennial, rising 

 gradually each year on the new sediment. This building- 

 up may be seen where a boulder or piece of rock is present 

 and becomes gradually embedded. On these grounds we 

 regard this habitat as migratory and comparable to the 

 flushes described by C. B. Crampton (2) ; the snow-flush 

 vegetation will, therefore, come under that author's group 

 of migratory plant formations. 



During spring the snow-flushes are soaking and their 

 moisture is retained far into the summer, hence in a moist 

 season they remain slimy and slippery underfoot. In a 

 dry summer (as in August 1911) they become cracked and 

 crusted. Although it may be surrounded by a green sward 

 of Alchemilla alpina with arctic-alpine grasses (Festuca, 

 Poa, Deschampsia, Nardus), the snow -flush is mainly dark 

 in colour except where tufts of Gnaphalium sujnnum, 

 the dark-green mats of Salix herbacea, or moss-tufts of 

 Polytrichum have become established. 



1 These characteristics suggest the term " snow-flush." The original 

 definition of "flush " hy C. B. Crampton (2) is : "Sloping ground gives 

 rise to springs. Where the springs are of small volume, or Avhere they 

 are of a temporary natui'e flowing only in wet weather, the growth of 

 plants prevents marked erosion of the surface and shallow gutters 

 floored with vegetation result. These may be called ' flushes.' The 

 vegetation and plant association of these flushes depends on the nature 

 and source of the flow of water " (p. 62). 



