40 Origin of the British Flora. 



channel across the low neck of land just beyond the 

 southern limit of the ice-sheet. Other parts of Britain 

 were hidden under ice-sheets whose gathering grounds had 

 other centres, and the result seems to have been the total 

 blotting out of the flora over the area north of the Thames 

 and Severn, with the possible exception of certain high 

 hills which rose above the ice. Even these were probably 

 so smothered with snow that only the steeper crags were 

 bare in summer. 



The condition of the greater part of Britain during the 

 climax of the Glacial Epoch will not, .therefore, greatly 

 interest the botanist. The flora was so nearly extermin- 

 ated that the interest is transferred to the non-glaciated 

 strip between the Thames and Severn and the English 

 Channel, and to a very small non-glaciated area in South 

 Wales. In these parts only could the Arctic plants and 

 mammals live, and the whole of Britain was so cold that 

 the temperate species must have entirely disappeared. 



Many naturalists will disagree with the statement that 

 has just been made ; for it has become almost an article of 

 faith that there were certain warm corners in these Islands 

 where the Temperate animals and plants could survive, and 

 where the peculiar Lusitanian flora of Cornwall and of the 

 West of Ireland lingered on till the renewed warmth 

 enabled the plants again to spread. It will be necessary 

 therefore briefly to summarise the evidence on which the 

 opinion above expressed has been founded.* 



The temperature of the sea and of the air do not neces- 

 sarily correspond in the same regions ; we will, therefore, 

 first discuss the evidence as to the lowest temperature of 

 the seas round Britain. For this purpose the former 

 southern limit of the formation of shore ice, or ' ice-foot,' 



* See ' The Climate of Europe during the Glacial Epoch,' Natural 

 Science, Vol. I., No. 6, pp. 427-433 (1892). 



