The Origin of our British Flora 



have been living in the sixth glacial stage, and to have 

 known nothing whatever about it ! 



But unfortunately for this explanation, the land is sup- 

 posed to have been 25 to 30 feet lower during the sixth 

 glacial stage, and if this is the case the Roman wall 

 should show that it was not intended to reach as far as 

 the modern sea-beach, but only to about 25 or 30 feet 

 above that level. Here, then, is a little antiquarian point 

 which turns out to be of great scientific importance ! 



Otherwise it is very difficult to understand why the 

 traditional Scotch forest has utterly vanished and left no 

 trace whatever in the uppermost or recent peat. But 

 there has not been yet, by any means, sufficiently exten- 

 sive researches to be sure if this is the case or not. 



On the Continent there are some authors who have 

 traced the effect on the plant world of quite similar 

 fluctuations of climate in the later stages of the Ice 

 Age. What corresponds to Geikie's sixth Ice Age is, for 

 instance, earnestly required by Schulz. 



The North German heath, a ^' mantle of coarse sack- 

 cloth with a border of silk," which occupies an enormous 

 area of North Germany, is supposed by Graebner to have 

 been once a Scotch pine forest. He, however, does not 

 think apparently that it was destroyed by man, but by 

 some climatic change or the impoverishment of the soil.^^ 



But in Switzerland and central Germany it is supposed 

 that the destruction of the forests by mankind took place 

 between 400 A.D. and 1200 A.D., which is just the period 

 during which our Scotch traditional forests were de- 

 stroyed. The reader will see how much has yet to be 

 discovered before it is possible to bring tradition and 

 antiquarian discoveries into line with modern geological 

 and botanical research. 



But leaving these interesting little details, it is clear 

 that, as regards our general British flora, it may'be con- 



230 



