SOME ALPINE CLIMBERS. 219 



pastures in the colder north survives on the limestone 

 cliffs of Ben Bulben in Sligo, and on a serpentine hill 

 at Unst in the Shetland Isles. One of the northern 

 chickweeds still keeps up its race more bravely under 

 adverse circumstances ; for it spreads over all the tallest 

 Scotch mountains beyond the Breadalbane range, and 

 also maintains its footing in the Irish hills near Bantry : 

 but if we may trust the ordinary analogies, it will gradu- 

 ally be driven from most of these stations till at last it 

 is confined to one solitary chilly summit, where it will 

 slowly die away from generation to generation. The 

 mountain known as the Sow of Atholl, in Perthshire, 

 has thus succeeded in preserving one of its ancient glacial 

 inhabitants, a blue heath known as Menziesia, now 

 rapidly verging to extinction. The Alpine astragalus 

 lingers on in the Clova and Bracmar range : its ally the 

 field oxytrope is also confined in Britain to a single spot 

 among the Clova hills. The saxifrages are a very glacial 

 group, and three or four of them are now distinctly 

 becoming more and more rare in individuals. One 

 species at present lingers with us only on the summit of 

 Ben Lawers ; another occurs on the same mountain, as 

 well as on Ben Nevis and Lochnagar ; a third is confined 

 to Ben Nevis and Ben Avers ; a fourth has several 

 Scotch and English colonies, but grows nowhere in Ire- 

 land except on the mossy sides of Ben Bulben. So, too, 

 the Alpine sowthistle is confined in these islands to Clova 

 and Lochnagar, while the mountain Lloydia is only 

 known on three isolated summits in the Snowdon range. 

 Almost all these plants are, in all probability, now 

 actually in course of extinction over the whole world ; 

 certainly they have long been growing scarcer and 



