DISTRIBUTION OF BRITISH PLANTS. 331 



different floras are supposed to have migrated. It will 

 assist us in forming such a notion to take a glance at a map 

 of Europe, across which we must imagine a line drawn, in- 

 tersecting England and Ireland in the middle, and continued 

 eastward till it strikes against the Ural chain. During an 

 epoch, called the glacial epoch, which is said to have been 

 immediately antecedent to the present state of our globe, all 

 the immense space on the north of this imaginary line is 

 supposed, from the remains which it still contains, to have 

 formed one vast icy sea, of which the Ural Mountains, 

 which were then a sea-side chain, formed the eastern boun- 

 dary ; the mountainous parts of Scotland, Wales, and part 

 of Ireland forming groups of comparatively low islands in 

 this glacial sea. It is believed to have been of a very simi- 

 lar nature to that which now bounds "the north-eastern 

 coast of America, within the line of summer-floating ice." 

 Over this icy medium the mountain (or Alpine) flora is sup- 

 posed, from the peculiarities of its character, to have mi- 

 grated from Scandinavia."* The climate of the whole of 

 Northern and part of Central Europe was then very differ- 

 ent from what it is now, and far colder, which is " indubit- 



* The peopling of the Scotch mountains by means of iceberg transport of 

 seeds is however objected to by Dr. Hooker. 



