

UPON THE BRITISH FLORA. 



and English types, and is represented in Dorsetshire by Clematis 

 Vitalba, Linurn perenne, Bryonia dioica, Gentiana Pneumonanthe , 

 Tamus communis, Inula Conyza. The pulmoniferous mollusc 

 Clausilia Rolphii, which I added to the list of Dorset shells last 

 year, is connected with the flora of this province. No. IV. 

 Includes the mountainous districts of Scotland, Cumberland, and 

 Wales. This flora is more arctic in Scotland than in the other 

 two. It produces Draba rupestris, Astragalus alpinus, Sibbaldia 

 procumbens, Arctostaphylos alpinus, Veronica alpina, Betida nana, 

 This is Watson's Highland type. No. V. General Flora, Watson's 

 British type. There are some local species which constitute his 

 Germanic, British, and Highland types. The scarcer plants of 

 this section show the line of migration in their advance westward. 

 Excepting Myosurus minimus, the Mousetail, none occur in this 

 county. A similar absence is observable among the Vertebrates 

 and Invertebrates ; the Mole, the Squirrel, the Polecat, the English 

 Hare (Lepus timidus), and numerous molluscs are restricted to 

 this side of the St. George's Channel. Forbes considered the 

 Lusitanian flora to be the oldest of the five provinces, and of the 

 Miocene Age, when the North Sea was of smaller dimensions 

 than at present ; it did not then touch our present coast-line. 

 By a subsequent enlargement a direct communication was made 

 with the Arctic Sea, occasioned by a sinking of land, through 

 which the North Sea and the Atlantic became connected. Plants 

 could then migrate on dry land without hindrance over France, 

 Spain, and England. The Scandinavian flora, which Sir Joseph 

 Hooker considers to be of great antiquity, was driven south on 

 the approach of the Glacial Age, the survivors of which returned 

 during the succeeding temperate period. During the Pleistocene 

 Age there is evidence of a period of cold succeeded by a milder, 

 and of sufficient length for the reappearance of a temperate flora. 

 It may be well to bear in mind that the climate was tropical and 

 subtropical at the commencement of the Tertiary period, and 

 gradually became more temperate towards its termination. When 

 the Red Crag of the Eastern Counties was being deposited the 

 temperature was much lowered, and during the succeeding 



