DISTRIBUTION OF PLANTS IN BRITAIN. 587 



lated to that of the north-west of France, extending from the Channel 

 Isles, across Devon and Cornwall, to the south-east and part of the 

 south-west of Ireland (Watson's Atlantic type). 3. A flora common 

 to the north of France and south-east of England, and especially 

 developed in the chalk districts (Watson's Germanic type). 4. An 

 Alpine flora, developed in the mountains of Wales, north of England, 

 and Scotland (Watson's Highland type). 5. A Germanic flora, ex- 

 tending over the greater part of Great Britain and Ireland, mingling 

 with the other floras, and diminishing, though slightly, as we proceed 

 westwards, indicating its easterly origin and relation to the character- 

 istic flora of northern Germany (Watson's British, English, and Scottish 

 types). In attempting to account for the peculiarities of these floras, 

 most of which had been previously noticed by Mr. Watson, Professor 

 Forbes enters into some geological speculations, which, although en- 

 tirely conjectural, are well worthy of consideration. He numbers in 

 ascending order these floras, according to their magnitude as to species, 

 and also, in his opinion, according to their relative age and period of 

 introduction into the area of the British islands. His conclusions on 

 this point are the following : 



"1. The oldest of the floras now composing the vegetation of the 

 British isles, is that of the mountains of the west of Ireland. Though 

 an Alpine flora, it is southernmost in character, and is quite distinct as 

 a system from the floras of the Scottish and Welsh Alps. Its very 

 southern character, its limitation, and its extreme isolation, are evi- 

 dences of its antiquity, pointing to a period when a great mountain 

 barrier extended across the Atlantic from Ireland to Spain. 



" 2. The distribution of the second flora, next in point of probable 

 date, depended on the extension of a barrier, the traces of which still 

 remain, from the west of France to the south-east of Britain, and thence 

 to Ireland. 



"3. The distribution of the third flora depended on the connexion 

 of the coast of France and England towards the eastern part of the 

 channel. Of the former existence of this union no geologist doubts. 



" 4. The distribution of the fourth, or Alpine flora of Scotland and 

 Wales, was effected during the glacial period, when the mountain 

 summits of Britain were low islands, or members of chains of islands, 

 extending to the area of Norway through a glacial sea, and clothed 

 with an arctic vegetation, which in the gradual upheaval of those 

 islands and consequent change of climate, became limited to the sum- 

 mits of the new-formed and still existing mountains. 



" 5. The distribution of the fifth, or Germanic flora, depended on the 

 upheaval of the bed of the glacial sea, and the consequent connexion 

 of Ireland with England, and of England with Germany, by great 

 plains, the fragments of which still exist, and upon which lived the 

 great elk and other quadrupeds now extinct. 



