86 Oscar Drude. 
Of these species I select Potentilla fruticosa, which we saw in 
the station figured by R. LI. Praeger in his “ Tourist’s Flora of the 
West of Ireland,” p. 140. This station has no special orographical 
features: it lies south of Galway Bay, almost at sea level, in a 
shallow depression of the cattle pasture. There, as Praeger says, 
the plant is dominant:—‘“ Generally abundant where it occurs, 
sometimes almost entirely usurping the ground over an acre or two, 
as behind Ballyvaghan,” (l.c.). Clare, Galway and Mayo contain the 
Irish Stations, the English belong to the second of the above 
mentioned regions. Nowhere else in the British Isles is the plant 
wild. Let us now compare the other European stations. The 
Pyrenean plant is reckoned as another species or at least a distinct 
race—P. prostrata Lap. In the often cited single German station, 
Wemding in the North Keuper district of Bavaria the plant may 
be regarded as dying out or perhaps as naturalised only. In 
addition there are South-East Russia and Oeland. These relict 
stations have no connexion with each other, and since Potentilla 
fruticosa is a plant of quite different climatic conditions from the 
chomophytes, its occurrence throws a bright ray of light on the post- 
glacial development of the British flora: the species has occupied its 
present stations since the Baltic ice period, if not longer. 
Carnarvon, in the north-west corner of Wales, is distinguished 
by the sole possession of Lloydia serotina. Saxifraga nivalis has 
here its southernmost station in the British Isles, reaching north- 
wards to 57°5° N. Saxifraga rivularis does not extend south of 
Ben Lawers, and ranges northwards to Westerness (57°N.) so far 
as I can follow the stations. Sagina nivalis is confined to Ben 
Lawers and quite a narrow area of the Scottish mountain region, 
S. saxatilis to the same region, from Ben Lawers to the north coast. 
These cases indicate the scattered type of distribution of the arctic- 
alpine plants of the British Isles. This is not, as in the Alps, a 
result of local endemism in the different regions combined with 
arctic invasion from the north, but rather a case of the colonisation 
of the arctic flora during the Glacial Period, the present fixed stations 
having been occupied at the close of the Baltic ice period. Dryas 
octopetala is one of the species which connects England, Scotland 
and Ireland, ranging from Carnarvon by Westmoreland to Perth 
and the Orkneys, and in Ireland is scattered over ten counties of 
Praeger’s map. The habitats of this species on Black Head, south 
of Galway Bay, are very remarkable. At slight altitudes (100 m.) 
on the limestone slopes it occurs with Euphrasia salisburgensis, 
