1911-12.] BOTANICAL SOCIETY OF EDINBURGH 37 



more restricted to sheltered places beside blocks. Here 

 the most conspicuous plant association is Rhacomitriv/m 

 lanuginosum with Ca/rex rigida and other mat-forming 

 plants, but at frequent intervals the darker patches occur. 

 The summit ridge shows many tracts of this black m 

 crust, and in the " Cernua Corrie " there is one large patch 

 at the rough wall near the ruins of the Ordnance hut. 

 One has also recollections of other summits where this 

 dark-crusted humous surface is a feature. 



The Swiss botanists recognised these patches and tracts 

 as " Schneetalchen," a term introduced by Oswald Heer in 

 1836. In L. Schroter's " Taschenflora " (3) the word is 

 translated as " snow- valley/' but as English equivalent 

 " snow-gutter " or " snow-flush " more nearly expresses the 

 kind of little runnels suggested by the original term. The 

 vegetation of these snow-flushes has been described by 

 authors like Kerner, Christ, Stebler, and Schroter. The 

 more recent observations of Brockmann-Jerosch (4) indicate 

 that, before dealing with the vegetation, attention should 

 be directed to the topographical and physical factors that 

 bring about its evolution. Anyone who has seen the snow 

 melting on the higher hills can recall the early emergence 

 of rocks or snow-bleached green slopes and knolls. In 

 Switzerland and the Tyrol these are bedecked with flowers 

 while the snow still lies a few yards away. Day by day 

 the snow-patches decrease, becoming more limited to the 

 lower depressions or sunless slopes. The snow-water soaks 

 through the turf seeking the lower depressions till it flows 

 from below the snow and streams away to still lower levels. 

 Thus in troughs and depressions of undulating ground and 

 along the foot of slopes or escarpments there is a system 

 of temporary water-courses which, so long as the snow is 

 melting, are more or less under water. The summer rain- 

 water will tend to follow the same course, but with this 

 difference that the larger supply of ice-cold water is replaced 

 by more occasional trickles of warmer surface-water. On 

 steep slopes these streamlets descend with some force and 

 carve out little stream-beds (snow-water channels), but on 

 gentle slopes or flats or in depressions the force of the 

 flow is not sufficient to erode ; the water wanders slowly 

 through the turf and deposits accumulated suspended 



