262 
THE GEOLOGIST. 
EoTAL Institution.— ilifarcA 7.—" On the Distribution of Northern 
Plants." By Professor D. Oliver. The discourse referred primarily to 
the botanical evidence bearing upon the hypothesis advanced by Pro- 
fessors Unger* and Heerf of an Atlantic communication between Europe 
and America at some period of the Tertiary epoch. The close analogy 
which is to be traced between the Miocene Flora of Central Europe and the 
existing Flora of the Eastern American States, these authors conceive can 
only be explained by assuming such direct overland connection of the two 
Continents. 
The speaker explained the basis upon which comparisons between two 
recent floras and between a recent and a fossil flora should rest, referring 
to the peculiar conditions which affect the latter comparison owing to the 
imperfect and partial character of the fossil element. The general cha- 
racter of the Tertiary Flora of Central Europe was described. In the 
Tertiary beds of Switzerland, according to Professor Heer j about 800 
species of Phanerogamia have been discovered, referable to 197 genera 
(exclusive of Phyllites, Carpolithes, etc.), of which number 154 still exist. 
Of these genera — 
76 are common to the Swiss Tertiary, 
and to the present flora of . . Europe. 
77 ...... . Japan. 
88 ...... . Ditto, States, America. 
120 ....... Euiope aud Asia (taken toge- 
ther, and including Japan). 
It is to be noted that the 77 of J^jpan include 26 not occurring in 
Europe : amongst them several forms highly characteristic of the Tertiary, 
as GJyptostrohus, numerous Fici, coriaceous-leaved oaks and Lauracece^ 
Juglandece, Liquid ambai\ etc. 
The genera, common to the Swiss Tertiary and the United States, which 
are not found also in the Old World are Sahaf, Taxodiiun, Bunielia, Lirio- 
dendron, Ceanothus, Ptelea, and Carya. But in respect to these 7 it was 
observed that at least 5 were very doubtful determinations. The 9 largest 
orders of the ' Flora Tertiaria Helvotiae ' are LegiiniinoscE, AmentacecB, 
CyjperacecB, Proteacece, LauracecE, Graminece, Conifercp, Composite?, and 
AceracecB. Of these Orders 3 are included in the 9 largest of Europe, 4 
in the 9 largest of the United States, and 6 in the 9 largest of Japan, 
while the remaining 3 of the Tertiary, not included in tlie 9 largest 
orders of Japan, are much more largely developed in Japan than in 
the United States. They are LauracefP, Aceracece, and ProteacecB. 
The proportion of ligneous to herbaceous species in the above floras 
was alluded to. Heer estimates ligneous plants to have formed about 66 
per cent, of the Phanerogamic vegetation of the Tertiary in Switzerland. 
The speaker considered this estimate as too high, believing that sufficient 
allowance had not been made for the advantages that ligneous plants, 
which are often tall-stemmed, possess over herbaceous species in securing 
access of their leaves and debris to the waters in which they had been 
floated, and ultimately preserved. He admitted, however, that ligneous 
species were relatively very numerous in the vegetation of the Tertiary 
period. The proportion of ligneous plants he estimates in the existing 
flora of Japan at near 40 per cent., in the Southern States 22, jS'orthern 
States 18, Europe 9 to 12. 
* ' Die versunkenb Insel Atlantis.' t ' Flora Tertiaria Helvetipe.' 
:|: The Tertiary d^a were throughout derived from the '' Flora Tertiaria Helvetise' of 
Professor Hecr. 
