70 DISTRIBUTION OF PLANTS 



nigrum are usually depressed to a very few inches, and 

 Salix herbacea is always very small. The natural size of 

 several alpine species does not exceed, and here rarely 

 attains, three inches. Sibbaldia procumbens, Gnaphalium 

 supinum, Silene acaulis and Saxifraga oppositifolia are 

 examples ; which indeed frequently do not exceed one 

 inch above the surface. Saxifraga stellaris, Aira alpina, 

 Luzula spicata, Polygonum viviparum, Juncus triglumis 

 and Alchemilla alpina are taller-growing species, although 

 here diminished to | or | of their full size. Ve- 

 getation is also sparing in quantity, as well as in size ; 

 and in many places not half covering the surface of the 

 ground. Naked rocks, or bare shingle and gravelly de- 

 tritus, are often more conspicuous than verdure. This 

 occurs especially on the granitic and porphyritic moun- 

 tains. The last hundred yards of ascent on Ben Nevis 

 is almost destitute of flowering plants, and the last 500 

 yds very thinly clad. The schistose mountains are much 

 better covered with vegetation, and hence it is usual in 

 our Floras to mention the habitation of plants as " espe- 

 cially on a micaceous soil." Patches of snow remain 

 unmelted through the year in this region; particularly 

 on the Nevis and Cairngorm mountains ; but it lies till 

 autumn, and sometimes through the whole year, on several 

 of the Grampians to the southward of these, as Loch-na- 

 Garr, Ben Lawers, Ben More, &c. Fresh snow falls 

 occasionally during summer, but speedily disappears in 

 July and August. The vicinity of snow-patches seems 

 rather to encourage than to repress vegetation, probably 

 by reason of the moisture from liquefaction. It is worthy 

 of remark also, that alpine springs of water excite the 

 growth of some species chiefly found in the plains, and 

 which are scarcely seen on the alps, except about the little 

 rills from such springs. Poa annua occurs thus. It may 

 be presumed from preceding remarks, that at this elevation 



