280 Matthews .— The Distribution of certain 
destruction of the pre-glacial flora of Britain and its re-immigration in post¬ 
glacial times. Clement Reid also maintains that, with the possible excep¬ 
tion of a few arctic plants, our flora is post-glacial in origin. ‘We have 
merely to account’, he says (1911), ‘ for the incoming of our existing flora 
after an earlier assemblage had been swept away almost as completely and 
effectually as the celebrated volcanic eruption wiped out the plants of 
Krakatao.’ Stapf (1914) sees ‘ no way out of the conclusions at which 
Mr. Reid and many years before him Professor Engler have arrived 
although he doubts whether certain elements in the British flora are 
explained ‘by chance and occasional introduction of seeds ’, as is propounded 
by Clement Reid. 
On the other hand, the hypothesis that much of the flora survived the 
glaciation of the country is not without its advocates. We have seen that 
Forbes, as long ago as 1846 , regarded our flora as derived from different 
parts of the Continent by successive overland migrations, and he came to 
look upon the Iberian element, which is found in the west of Ireland, as the 
oldest, dating back to a time when a mysterious ‘ Atlantis ’ connected 
Ireland and Spain. Students of the Irish flora and fauna have done much 
to substantiate Forbes’s hypothesis. Zoological evidence bearing on the 
‘Atlantis’ problem is discussed by Scharff (1902), and the same author 
(1912) disputes the idea of a wholesale destruction of the flora which 
occupied Britain in pre-glacial times. Kennard and Woodward (1917), 
dealing with the post-Pliocene non-marine Mollusca of Ireland, also support 
the survival hypothesis, and Praeger (1910), writing of the Pyrenean plants 
in the west, describes them as ‘ relics of a vegetation which once spread 
along a bygone European coast-line which stretched unbroken from Ireland 
to Spain ’. Further evidence in support of survival from early Tertiary 
times is provided by three American species— Spiranthes Romanzoffiana , 
Cham., Sisyrinchium angnstifolium , Mill., and Eriocaulon septangulare. 
With. These occur in Ireland, the last in the west of Scotland also, and it 
is held that they must be members and relics of a pre-glacial flora which 
occupied a northern continent linking Europe and America across the 
North Atlantic. , 
The problem of the origin and distribution of any flora is so intimately 
related to the question of slow overland migration versus other possible 
methods of dispersal, such as water-currents, wind, or migrating birds, that 
mention must be made of it. A particular case, not incomparable with 
that of Britain after glaciation, is that of the Faeroes, discussed by both 
Ostenfeld (1901) and Warming (1903). Both agree that the present flora is 
post-glacial and that re-colonization from sea-borne or bird-carried seeds has 
been insignificant. Warming believes the wind is responsible for the 
introduction of most of the plants now found on the islands, while Ostenfeld 
holds that invasion took place over a post-glacial land bridge. Holttum 
