12 UPON THE FLORA OF THE SHETLAND ISLES. 
feet on Ronas Hill, and its flora is represented by Azalea procumbens, 
Carex rigida, Saussurea alpina, Alchemilla alpina, Salix herbacea, Sib- 
baldia procumbens. 
As regards the geological distribution of the plants little can be 
said, for though the lithologieal eharacters of the rocks are so varied, 
and though the rocks appear at the surface, and thus present conditions 
favourable for the modification of the flora, yet little influence is 
exerted upon the vegetation. That of the Serpentine and Euphotide 
rocks presents some prominent features; peat, which is generally so 
abundant on the gneiss, mica, slate, grauite, and sandstone, is almost 
absent on the Serpentine and Euphotide ; Arabis petrea, Draba in- 
cana, Arenaria Norvegica, Cerastium latifolium, Anthyllis vulneraria 
are restricted to them. 
The granite of Ronas Hill yields many peculiar plants, but they owe 
their presence to the superior altitude (1476 feet) of the hill on which- 
they occur as subalpine forms of vegetation, and cannot be regarded as 
truly granite-loving species. 
The plants restricted to a sandy soil have been already given. 
IV. COMPARISON OF THE FLORA OF HETLAND WITH THAT OF 
THE ORKNEYS AND THE FEROES. 
slate, gneiss, and granite; the latter by grits and sandstone. Little 
or no drift-matter encumbers the solid rocks. Whilst, on the one hand, 
the rock-formation of the Feroes is basalt, said to be com 
poor in species, on the other, the rocks of th 
to the sedimentary series, 
paratively 
e Orkneys all belonging 
are sandstones, grits, and argillaceous 
sandstones. It is therefore a very interesting subject of inquiry, as to 
the botanical relation existing between these three groups of islands. 
very marked differences in climate exist between the Feroes, 
Shetlands, and Orkneys; the mean annual temperature of the most 
northern group of islands is 45°16, being very little below that of the 
Orkneys, which is 46°-204, whilst it exceeds that of the Shetlands by 
0°434. Though there is such a similarity in climate between the 
