68 - - REPORT—1845. 
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-west of Britain, and thence to Ireland. 
3. The distribution of the third flora depended on the connexion of the coasts of 
France and England towards the eastern part of the Channel. Of the former exist- 
ence of this union no geologist doubts. 
4, The distribution of the fourth, or alpine flora of Scotland and Wales, was ef- 
fected 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 
the land 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 connexion 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 destruction of the 
second; that of the second to that of the third; but the well-marked epoch of the 
Germanic flora indicates the subsequent formation of the Straits of Dover and of the 
Trish Sea, as now existing. 
To determine the probable geological epoch of the first or west-Irish flora,—a frag- 
ment perhaps with that of north-western Spain, of the vegetation of the true Atlantic, 
—we must seek among fossil plants for a starting-point in time. This we get in the 
flora of the London clay or eocene, which is tropical in character, and far anterior to 
the oldest of the existing floras. The geographical relations of the miocene sea, indi- 
cated by the fossils of the coralline crag, give an afterdate 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 incoming of the second flora; that of the mammaliferous 
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, so far as animal life is concerned, exist southwards of the second and third 
barriers. This was the newer pliocene epoch. The period of the fifth flora was that 
of the post-tertiary, when the present aspect of things was organized. 
Adopting such a view of the relations of these floras in time, the greatest difficul- 
ties in the way of changes of the earth’s surface and destruction of barriers—deep sea 
being now found where land (probably high land) was—are removed when we find that 
those greater changes must have happened during the epoch immediately subsequent 
to the miocene period; for we have undoubted evidence that elsewhere, during that 
epoch, the miocene sea-bed was raised 6000 feet in the chain of the Taurus, and the 
barriers forming the westward boundary of the Asiatic eocene lakes so completely 
annihilated, that a sea several hundred fathoms deep now replaces them. The 
changes required for the events which the author would connect with the peculiar 
distribution of the British flora need not have been greater than these. 
Prof. Forbes maintains that the peculiar distribution of endemic animals, especially 
of the terrestrial mollusca, bears him out in these views. He proposes to pursue the 
subject in detail, with reference both to animal and vegetable life, in connexion with 
the researches of the geological survey. 
On the Development of Vegetable Cells. By A. Henrrey, F.L.S. 
After noticing the opinions of MM. Mirbel, Schleiden, Mohl and Nageli, he stated 
the conclusions to which he had been conducted by observations, viz.—1. That there 
is no such thing as the interruption of continuity between the liber and alburnum, 
called the cambium layer. 2. That the potentiality of the black granules described 
by Schleiden is not proved, and that the utricle first developed from the so-called 
cytoblast is not the permanent cell, but the primordial utricle of Mohl, the existence 
of which in growing tissues seems to be universal. 3. That this primordial utricle is 
not a layer of mucilage, as stated by Nageli, but a true membrane. The author re- 
gards the nucleolus, or central spot of Schleiden’s cytoblast, as the germinal point, and 
as situated on the wall of the primordial utricle. When a new cell is to be formed 
' 
» 
