326 Matthews. — The Distribution of Plants in 
times, but extending far south into England during late Pleistocene (Bennie 
(1896), Lewis (1911), Reid (1911), Chandler (1921)). 
It has been estimated that about 13,000 years have elapsed since the 
beginning of emergence of Scotland and Scandinavia from the ice cap of 
the last glacial period. Since then an arctic flora has almost disappeared. 
Numerous species once occurring in Britain are now extinct. Those that 
remain are confined to our higher hills, and while they may not be visibly 
Fig. 2. * 
disappearing, except from the extravagance of collectors, they must, on 
a long view, be regarded as relics of an outgoing flora. They are members 
of that palaearctic flora which once girdled the globe in high latitudes, and 
which, I believe, will be found to provide a greater number of relics than 
occurs in a tropical flora. The bulk of the returning, incoming temperate 
flora, which has replaced the earlier more arctic assemblage, I regard as of 
comparatively recent date. Much of it is due to and depends upon man’s 
occupation of the country. But as man’s migrations and operations must 
have been determined broadly by the time factor, so would the migration 
