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LINNEAN SOCIETY OF LONDON. 228
tliougli doubtless only a portion of the plants wliicli took possession
of the island as its ice-covering disappeared, suilice to give us a
general idea of the vegetation. Mr. Carruthers referred to the
labours of H. C. Watson and E. Forbes in connection ^Yith the
geographical distribution of our existing Flora, and cited the
observations of Darwin, J. D. Hooker, and Hemsley, on insular
Floras, with the more recent ones of Dr. Treub on the beginnings
of vegetation at Krakatao, as showing that, in the case of new
islands, whether of coral or volcanic origin, the first vegetation is
borne by water and air-currents. Returning to our own island,
Mr. Carruthers gave a sketch of its condition when the first members
of our present Flora made their appearance. " The Tertiary
Period had closed. Only in the immediately preceding Upper
Cretaceous rocks had there been any association of species in a
Flora analogous to the geographical groups of our own day. The
plants that have been discovered in the Eocene beds possess the
facies of a tropical Flora ; the Miocene plants indicate a slight
decrease in temperature, and this continues till we reach the subtropical
Flora of the Pliocene. Then there appeared a remarkable
change in the climate, and the Pliocene plants perished before the
advancing boreal cold. The Pliocene plants do not belong to the
same genera, seldom even to the same orders, as the Flora which
follows ; and they conld not consequently have any ancestral rela-
tion to it. The cold that drove before it the subtropical vegetation
was the forerunner of the ice age. Advancing in front of the ice,
the first representatives of our existing Flora reached us from the
north, where they had not however long established themselves,
seeing that the tropical and subtropical floras of the Tertiary Period
flourished far within the arctic circle. The remains of these
earliest members of our present vegetation are buried in the Cromer
Forest bed with the bones of the extinct mammoth, the rhinoceros,
the hippopotamus, and the cave-bear, and of the still living horse,
red-deer, beaver, mole, &c. Only in a single case has it been
impossible to correlate what appear to be empty follicles with the
corresponding parts of an existing plant ; and it is possible these
fruits may represent an extinct species, though the imperfect
materials could not justify our asserting this without great reserve.
Three of the species are no longer members of our existing Flora,
though they still persist, like the beaver, in other lands."
Mr. Carruthers proceeded to enumerate and group geographically
the 53 species of plants found in the Cromer beds, which, with two
exceptions, Salix polar in and Jli/iniuni tHi(fc.sccns, belong to the
Germanic type of our Flora. Two of the Cromer plants, Trapa
iiiiUtiis and I'niuH ^lliiis, liave lieen lost to us, driven from our laud
befcn'e the advancing cold, and having failed to return when the ice
retreated.
After further remarks on distribution, Mr. Carruthers concluded
as follows :
" Various estimates have been made of the centuries that have
run their course since the glacial epoch. Beyond the date at
which man began to record time we can have no definite informa-