December, 19 1 1 T/ie Irish yaiiiralist. 20I 



THE RELATION OF THE PRESENT 



PLANT POPULATION OF THE BRITISH LSLES 



TO THE GLACIAL PERIOD. 



BY CLEMENT KEID, F.K.S. 



[The lollow iii.n comiuunicatioii, made lo n joint meeting of the Botanical 

 and Geological Sections of th< British Association at the receiit meeting 

 at Portsmouth, was brought forward by Mr. Clement Reid as the opening 

 to a discussion on the subject to which it refers — a discussion in which 

 Dr. Scharff, Dr. Stapf, Professor Schroeter, Mr. W. B. Wright, Professor 

 Drude, F. J. Lewis, Dr. Ostenfeld, and Dr. Arber took part ; also, by 

 means of letters. Dr. A. R. Wallace, Dr. Marr, and Professor Kendal. In 

 view of the discussion on this and kindred subjects that have recently 

 taken place at the Dublin and Belfast Field Clubs and elsewhere, Mr. 

 Reid's opening statement is of interest to our readers^none the less so 

 since Mr. Reid's views differ widely from those held by the majority of 

 Irish Naturalists — and by permission of the author and the Council of 

 the Association, we reprint it here. — Eds.] 



The distribution of our British plants has long been a puzzle 

 to the botanist, and no explanation was forthcoming till the 

 cause was searched for in bygone changes of climate, and 

 changes in the distribution of land and sea. A century ago 

 it was generally supposed that species had originated mainly 

 in the districts in which they were then found. But even 

 under this hypothesis the anomalies of discontinuous areas 

 seemed to require explanation, for the same species was not 

 likely to originate at several different points. 



With the growth of the idea of gradual evolution it was 

 realised that faunas and floras had a past history, even if 

 the included species had remained unchanged. Botanists 

 recognised that there were many points that required ex- 

 planation. For instance, it was noticed at an early date 

 that each of our mountain-tops- possessed a small outlying 

 fragment of the arctic flora. How came it that the same 

 species occupied so many different mountains ? This 

 seemed a perfectly fair subject of inquiry, even to naturalists 

 who hated the very idea of evolution when applied to 

 species and genera. 



More than sixty years ago a great impetus was given to 

 this study by the discovery that Europe had passed through 

 a most remarkable series of climatic changes, and that, too, 

 during the lifetime of the existing species of animals and 

 plants. There had not been a mere cooling of the climate ; 



