io8 The Irish Naturalist. June, 



Birch and some arctic Mosses had been discovered in 

 alluvial deposits. Here, he says, is evidence of the extreme 

 rigour of climate that the botanist himself must accept as 

 conclusive. And do botanists as a whole really accept the 

 evidence referred to as conclusive ? Most plants, no 

 doubt, are trustworthy tests of climate. Yet if we wish 

 to grow arctic or alpine plants in health and vigour, we do 

 not provide them with a low temperature. On the con- 

 trary, we find that while they endure the greatest summer 

 heat with little injury, they are mostly destroyed when 

 insufficiently protected against frost. In their native 

 habitats they are sheltered by the winter snow from ex- 

 posure. Hence it is permissible to argue that these plants 

 may once have lived in countries possessing an equable 

 climate. The fact of their having formerly inhabited the 

 south of England does not necessarily imply that an arctic 

 climate prevailed there. Has Mr. Reid forgotten that one of 

 the most typically arctic plants — the Mountain Avens 

 [Dryas octopetala) grows wild in profusion close to sea-level 

 near Galway, the average winter temperature of that part 

 of Ireland being 44*^F, or 12^ above freezing point? The 

 tough leathery leaves of this plant are exceptionally well 

 suited for preservation. If from some unknown cause this 

 habitat of Dryas octopetala were now destroyed, future 

 generations might find the imprints of the characteristic 

 leaves of this plant, possibly without any admixture of 

 other species, in the clay. Some future botanists might 

 then be disposed to argue from this deposit that an arctic 

 climate must have prevailed in Ireland within recent 

 times. 



Mr. Reid, however, quotes one more piece of evidence 

 in favour of his contention as to the former extreme rigour 

 of the climate in the south of England. Close to Salisbury, 

 he says, are found in profusion remains of various arctic 

 mammals such as the Reindeer, Musk Ox, Arctic Fox, 

 Lemming, and others. Mr. Reid thus leads us to suppose 

 that in such an assemblage of arctic animal remains we 

 possess clear evidence of the former prevalence of an ex- 

 tremely rigorous climate. This is quite a mistake. These 

 animals are not dependent on a cold climate. The Reindeer, 



