IV. The summits of our British Alps have always yielded to the botanist a rich harvest of plants which he could not meet with elsewhere among these islands. The species of these mountain plants are most numerous on the Scotch mountains,—comparatively few on more southern ridges, such as those of Cumberland and Wales. But the species found on the latter are all, with a single exception (Lloydia serotina), inhabitants also of the highlands of Scotland; whilst the alpine plants of the Scotch mountains are all in like manner identical with the plants of more northern ranges, as the Scandinavian Alps, where, however, there are species associated with them which have not appeared in our country. This progressive diminution of alpine forms southwards is an important fact, the interpretation of which will presently appear.
The first plant of this Scandinavian type which disappears southwards is the Arenaria norvegica, confined to the most northern of the Shetland Isles. On the northern shores of the mainland a beautiful primrose, the Primula scotica, formerly supposed to be peculiar to the country after which it is named, but found by me abundantly in Norway in 1833, appears and ceases. A rich assemblage of these northern forms are distributed over the Scottish Alps, but do not reach the English mountains. Such are Draba rupestris, Lychnis alpina, Arenaria rubella, Astragulus alpinus, Sibbaldia procumbens, Saxifraga cernua, Saxifraga rivularis, Arctostaphylos alpina, Phyllodoce cœrulea, Azalea procumbens, Gentiana nivalis, Myosotis suaveolens, Veronica alpina, Veronica saxatilis, Salix arenaria, Betula nana, and many species of Juncus, Luzula, and Carex, Of these the Phyllodoce cœrulea (a plant highly characteristic of the Norwegian Alps) has either disappeared lately, or is likely soon to be extirpated, having fallen a victim to the ardour of collectors, who will, probably, ere long, extirpate many more of our alpine rarities, and reduce them to the rank of doubtful natives—like Eriophorum alpinum, now certainly extinct. To the same category with the above belong some plants less truly alpine, and not ranging south of Scotland, as Moneses grandiflora, Pinguicula alpina, Ajuga pyramidalis, Goodyeria repens, 'Corallorhiza innata, and certain species which reach the north of England, as Cornus suecica, Linnæa borealis, and Trientalis Europæa, all very characteristic Scandinavian species. To the Welsh mountains but few of these alpine and northern forms reach, but among them are some of the most characteristic. Such are Arabis petræa, Cerastium alpinum, Potentilla alpestris, Sedum villosum, Saxifraga muscoides, Saxifraga nivalis, Erigeron alpinum, Salix reticulata and herbacea, Juncus filiformis, and Juncus triglumis.
In Ireland, also, a few of these alpine or sub-alpine plants of Scandinavian origin are found, probably derived from the same source, and
