42 Origin of the British Flora. 
Remains of this boreal fauna and flora have now been 
found at several places in the south of England. A large 
assemblage of Arctic mammals has been discovered near 
Salisbury, and it includes such thoroughly boreal forms as 
the Musk Ox, Arctic Fox, and Lemmings. Even in what 
is now one of the warmest parts of our Islands, Arctic 
plants occur in the fossil state; for Bovey Tracey, in 
Devon, yields the Dwarf Birch, and the Bearberry. This 
leaves no place of retreat within these islands for the 
Temperate animals and plants. All Ireland was glaciated, 
so nothing could live there, except perhaps a few Arctic 
plants on the mountain-tops. All England was under ice, 
except the extreme south; and there the climate was too 
cold for temperate plants to live. It may be suggested 
that the Scilly Islands were warmer, and perhaps they 
were somewhat better than Devon and Cornwall. But this 
will not account for the preservation of the Lusitanian 
Species, for most of them are not found on the Scilly 
Islands, and plants like the Avdutus would be killed by a 
climate only slightly more severe than that now found in 
Ireland. 
After the passing away of the ice there was a return to 
genial conditions, which lasted so long that during this 
‘Inter-glacial’ period a series of physical changes took 
place, and there was time for the Arctic species to die out 
and for a large Temperate fauna and flora to occupy the 
country. We do not yet know the history of some of the 
stages, as there are several gaps in the record ; the changes, 
however, were slow and gradual, allowing time for valleys 
to be deepened and again silted up, for sea-cliffs to be cut 
back, and for plants to spread far and wide over new 
districts. During the greatest intensity of the cold, as we 
have shown, there seems to have been a submergence of a 
few feet. Then comes a break for which the records have 
