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LIKNEAN SOCIETY OF LONDON. 83 



happened along with the repopulatiou of the eglaciated land by 

 a llora advancing mainl}" from south-western Europe through 

 w^estern France,, where the improvement of the climatic conditions 

 following on the retreat of the ice in the north set in first. It 

 might be sufficient to refer to the pnges quoted from his book, if 

 it were not for the brevity with which lie was obliged to deal with 

 the matter and for the fact tliat great confusion exists as regards 

 the meaning of the terms "Atlantic," " Pyreneau " or " Lusi- 

 tanian " plants and the place which these elements hold in the 

 British flora and its history. I have therefore thought it useful 

 to sort out from the British flora that constituent portion which 

 from its distribution in Europe might justly be called " Atlantic," 

 and to analyse it with regard to the relative continuity or dis- 

 continuity of the British and Continental areas of its members. 

 In doing so it became evident, as was to be expected, that the 

 " Atlantic " fraction of the flora could not be separated from 

 another portion which whilst covering the Atlantic region 

 extended beyond it into the Mediterranean region, of which it is a 

 characteristic part. In fact they belong to the same Southern 

 stock, but with this difference, that one is more specialized with 

 respect to the conditions whicli determine the distribution of its 

 members than the other. The scope of my analysis had therefore 

 to be extended, so as to include both. The former are the 

 " Atlantic " and the latter the " Mediterranean " types as under- 

 stood in this essay. 



I have not considered it necessary to enter into the question 

 whether these Atlantic and Mediterranean types have survived the 

 Glacial period in Great Britain and Ireland or whether their pre- 

 sent habitats in those islands are post-glacial. Whether one accepts 

 the " land-ice " or the " submergence " theory, both of wliich 

 have been dealt with so admirably by Professor Bonney (5), the 

 botanist cannot but assume that survival under the rigorous 

 conditions postulated by both theories was impossible for most or 

 probably all the plants under consideration. If in the future new 

 facts should come to light which make the climatic conditions 

 during the Glacial period appear more favourable for plant-life, 

 the question of survival will have to be reconsidered ; but at 

 present I see no way out of the conclusions at which Mr. Eeid, 

 and, many j'ears before him. Professor Engler have arrived. 



The term "Atlantic type " was formulated by H. C. Watson iu 

 his ' Bemarks on the Geographical Distribution of British Plants ' 

 in 1835. There on p. 86 he says : " The Atlantic type embraces 

 species found in the south-west of England or Wales, sometimes 

 very locally, sometimes extending far along the southern or 

 vi'estern counties, but rare or wanting on the east coast. Some 

 plants of very limited geographical extension are common to this 

 part of Britain, the west of France and Portugal. Erica ciliaris, 

 Sihtliorpia europcea, Eupliorhia Peplis, Bartsia viscosa, and Pin- 

 guicula lusitanica may be given as examples of the type." From 

 the reference to France and Portugal it might be inferred that he 



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