British Association. 127 
flora of northern Germany. Interspersed among the members of the 
last-named flora, are very few specific centres peculiar to the British 
Isles. The author numbers in ascending order these floras, accord- 
ing to their magnitude as to species, and also, in his opinion, accord- 
ing to their relative age and period of introduction into the area of 
the British Islands. His conclusions on this point are the following : 
1. The oldest of the floras now composing the vegetation of the 
British Isles is that of the mountains of the west of Ireland. Though 
an alpine flora, it is southernmost in character, and is quite distinct 
as a system from the floras of the Scottish and Welsh Alps. Its very 
southern character, its limitation, and its extreme isolation are evi- 
dences of its antiquity, pointing to a period when a great mountain 
barrier extended across the Atlantic from Ireland to Spain. 
2. The distribution of the second flora, next in point of probable 
date, depended on the extension of a barrier, the traces of which 
still remain, from the west of France to the south-east of Britain, 
and thence to Ireland. 
3. The distribution of the third flora depended on the connexion 
of the coast of France and England towards the eastern part of the 
Channel. Of the former existence of this union no geologist doubts. 
4. The distribution of the fourth, or alpine flora of Scotland and 
Wales, was effected during the glacial period, when the mountain 
summits of Britain were low islands, or members of chains of islands, 
extending to the area of Norway through a glacial sea, and clothed 
with an arctic vegetation, which, in the gradual upheaval of those 
islands and consequent change of climate, became limited to the 
summits of the new-formed and still existing mountains. 
5. The distribution of the fifth, or Germanic flora, depended on 
the upheaval of the bed of the glacial sea, and the consequent con- 
nexion of Ireland with England, and of England with Germany, by 
great plains, the fragments of which still exist, and upon which lived 
the great elk and other quadrupeds now extinct. 
The breaking up or submergence of the first barrier led to the de- 
struction of the second; that of the second to that of the third; but 
the well-marked epoch of migration of the Germanic flora indicates 
the subsequent formation of the Straits of Dover and of the Irish Sea, 
as now existing. 
To determine the probable geological epoch of the first or west- 
Irish flora,—a fragment perhaps with that of north-western Spain, of 
a vegetation of the true Atlantic,—we must seek among fossil plants 
for a furthermost starting-point. This we get in the flora of the 
London clay or eocene, which is tropical in character, and far ante- 
rior to the oldest of the existing floras. The geographical relations 
of the miocene sea, indicated by the fossils of the crag, give an after- 
date certainly to the second and third of the above floras, if not to the 
first. The epoch of the red or middle crag was probably coeval with 
the second flora; that of the mammaliferons crag with the third. The 
date of the fourth is too evident to be questioned ; and the author 
regards the glacial region in which it flourished as a local climate, 
of which no true traces, as far as animal life is concerned, exist 
