lOO 



The Naturalist. 



II. As to the lichen — Cetraria islandica — which I lately came 

 across in fine large condition, and in some plenty, growing amongst 

 the fallen fir-needles, that make such a pleasant carpet for the foot, 

 in the large pine-woods to the east of Market Easen. This is an 

 unexpected and somewhat singular discovery, because ordinarily, in 

 England at any rate, the Cetraria is a high alpine or infer-arctic 

 species. It at once called up to Dr. H. F. Parsons (to whom I sent 

 a specimen) the Rev. W. Fowler's discovery, a few years back, of 

 Lycopodium alpinum on Crossby Warren, near Frodingham : a fact so 

 very strange that when told me, my state of belief in its natural 

 occurrence upon a Lincolnshire Warren not much above sea-level, 

 may be expressed in Cowper's lines : — 



Affirmat A. {Eev. W. Foioler) : 



Yes (rather moved), I saw it with these eyes." 

 Respondet B. (F. Arnold Lees) : 



" Sir, I believe it on that account alone ; 

 I would not, had I seen it with my own." 



Pleasantry apart, however, I take the one fact to be corroborative of 

 the other ; or rather, since our theories of distribution must give way 

 to, or be made to fit in with facts, I look upon both of these very 

 startling occurrences not as instances of peculiar powers of self 

 dispersion ; but in preference I see in them examples of highly 

 developed faculties for resistance, or elastic adaptation, to changing 

 conditions of climate ; thus enabling the species possessing such facul- 

 ties to hold on instead of succumb in that struggle for existence going 

 on all around us in the world of flowers as well as in the world of flesh. 

 From this point of view they are last links in a chain of changes 

 connecting the present time with an era, probably immediately sub- 

 sequent to the eons of the ice age, when Lincolnshire, level as it is, 

 had a flora as wholly arctic or boreal as Iceland has now. These 

 plants were not the outliers of a centre of dispersion situated some- 

 where on the Grampian or Cumbrian mountains ; but, in this view, 

 the arctic species that still may be found on those hill-ranges, equally 

 with the two Lincoln ones in question, are relics left stranded, where 

 we find them, as the tide of ice and cold retreated into more northern 

 regions. Those left on our mountains are more numerous because 

 the altitudes at which they exist have precluded competitors of 

 tenderer constitution from disputing the ground so hotly as they 

 - — emigrants advancing from the south — have done everywhere 

 in England on the lower levels. What a wonderful power of fight 



