



| 
24 FLOWERING PLANTS 
an average feiaporate approaching that at the sea-level in 
the arctic circle. 
_ (3) A sub-arctic flora is found over a great part of Seotland 
and on isolated hills in Britain. 
_ These represent the continental flora, if it may be thus eX- 
pressed, of Britain. 
Besides the above, there are two very specialized floras— 
namely, the aquatic flora of the eastern counties and the flora 
of Devon, Cornwall, and West Ireland, in which plants 
_ characteristic of the Pyrenean region are found. This last is 
known as the Lusitanian flora. 
There are several theories as to the way in which plants of 
the Pyrenean region could have reached West Ireland: from 
the fact that these plants have for the most part minute seeds, 
it has been suggested that migrating birds carried the seeds 
across. If, as is now generally thought, the western coast-line 
of Europe was far more extended than it is at present, and 
that land which is now submerged was once above water, it is 
very probable that the plants were able in those past ages to 
migrate overland, and have remained in Devon, Cornwall, 
and Ireland, owing to the milder climate. 
It. will be clear from what has been said in this chapter how 
necessary the study of geology is for a right understanding of 
the origin of floras. 
BIBLIOGRAPHY. 
‘The Origin of the British Flora”: Reid. 
