210 BRITISH PLANTS 
The past history of the British flora, then, is part and 
parcel of the history of the flora of Northern Europe. 
The population of this region with its present plants 
dates from the close of the Ice Age. During the Glacial _ 
Epoch Northern and Central Europe were completely 
buried beneath a sheet of ice, much as Greenland is 
to-day. The vegetation previously existing was de- 
stroyed or driven south into Northern Africa, which was 
then connected with Europe by several land - masses 
stretching across what is now the Mediterranean Sea. 
As the Ice Age passed away, and warmer conditions pre- 
vailed, the ice melted, and the bare earth became ex- 
posed. A great host of advancing forms moved north- 
ward in the track of the retreating glaciers, and repopu- 
lated the abandoned territories. At first the soil, so 
recently relieved of its icy burden, provided but a poor 
habitat for plants. The climate also was still very cold. 
The pioneers of the migration were those plants which 
were fitted to endure the greatest hardships. At first 
they had no competitors. The struggle for existence was 
not with one another, but with the hardships of their 
environment. But as time went on, and climatic condi- 
tions improved, fresh invaders appeared in the territories 
prepared by the pioneers ; fierce competition ensued, and 
while some seized, as conquerors, the pleasant places, 
others were driven to seek refuge in less favoured habitats 
or perished. In the struggle the pioneers were the 
first to suffer. Accustomed to live, unmolested by 
competitors, in cold or alpine conditions, they were 
unable to compete successfully with their rivals, and 
before the advance of lowland and temperate forms, 
this vanguard of the northern plant - migration was 
restricted to the mountains, where its descendants still 
remain. 
The alpine flora of Europe is almost the same every- 
where. The same flowers grow on the mountains of 
Wales and Scotland as on the Scandinavian highlands, 
the Alps, and the Pyrenees. Stranger still, the alpine 
flora of Africa, America, and even Australia and New 
Zealand, differs little from our own—so little, indeed, 
that some have suggested that the Scandinavian flora 
once dominated the earth, and that its remnants survive 
upon the highlands everywhere to this day. 
