EDWARD FORBES 27 



of a country could not be solved from biological studies alone, 

 but would require in addition the evidence supplied by 

 geology in regard to former changes in climate, land, and 

 water. Dealing with the flora of the British Islands, he 

 distinguished five sub-floras or assemblages of plants — (1) 

 a limited " Lusitanian " flora in the west and south-west of 

 Ireland, comprising saxifrages, heaths, the arbutus, a Pin- 

 guicula, and other plants which are identical with species 

 found abundantly in the north of Spain ; (2) another local 

 flora in the south-west of England and south-east of Ireland, 

 resembling the vegetation of the Channel Isles and North- 

 western France ; (3) a restricted flora found on the chalk 

 downs of the south-eastern counties of England ; (4) a 

 remarkable though limited flora, flourishing on the tops of 

 the mountains, chiefly in Scotland, but also on the hills of 

 Cumberland and Wales, and even on some uplands in Ireland, 

 in which vegetation all the plants are speciflcally identical 

 with Scandinavian forms ; (5) and last, a general or Germanic 

 flora, like that of Central Europe, everywhere present either 

 alone or mingled with the others. 



Forbes accounted for this distribution of the flora by 

 migration or colonization from neighbouring lands previous 

 to the isolation of the British Islands from the rest of Europe. 

 He supposed that the southern parts of our islands were 

 probably not submerged under the glacial sea, and that 

 over land now covered his three southern assemblages of 

 plants may have migrated successively northwards from 

 Spain and from France, before, during, or after the Ice Age. 

 If the floor of our seas was raised by even 100 fathoms, the 

 British Isles would become a part of the European continent, 

 the North Sea would become a great plain continued south 

 and west through what is now the English Channel, and a 

 strip of land would run from Britain along the west coast 

 of France so as to join the north of Spain. This was the 

 " Continental Platform " over which, according to Forbes, 

 the plants, and even possibly some of the lower land animals, 



