On the Origin and Distribution of the British Flora. 71
first of these lines of passage Mr. Darwin has suggested3 that
the northern forms existing in their own homes in greater
numbers, owing to the greater extent of land in the north,
have attained a higher stage of perfection or dominating
power; but Dr. Asa Gray's4 botanical confirmation of the
truth of Bishop Berkeley's dictum that "westward the
course of empire takes its way" remains at present an
ultimate fact.
In seeking for the geological origin of our existing floras it
seems of little use to travel backwards beyond the Cretaceous
period. The flora of the Jurassic consists mainly of ferns,
conifers and cycads, the oldest known dicotyledon being a
species of poplar (Populus primeva), found in beds of Middle
Neocomian age at Koine, in North-west Greenland;6 the
flora of this locality consisting in the main, however, of
ferns and conifers, among the latter being the genus Sequoia.
At the neighbouring locality of Atane a totally distinct flora
is found,6 in beds belonging to the Upper Cretaceous, and
including, with few cycads, sequoias, and other conifers, a
predominance of dicotyledons ; among which are a fig, two
magnolias, and plants apparently belonging to the orders
must have first become fit for organic life, Count Saporta proceeds to
assume that the termination of the azoic period coincided with a cooling
of the waters to the point at which coagulation of albumen does not take
place, when organic life appeared in the water itself.....The Polar area
was the centre of origination of all the successive phases of vegetation that
have appeared on the globe, all being developed in the north; and the
development of flowering plants was enormously augmented by the intro-
duction during the latter part of the secondary period of flower-feeding
insects, which brought about cross-fertilisation."
3 'Origin of Species,' chap. xii., p. 340, in ed. 6.
4 'Darwiniana.'
5 Professor Nordenskjold, in a lecture to the Royal Swedish Academy,
given in the 'Geological Magazine,' November, 1875, p. 529 ; and Professor
Oswald Heer, in 'Flora fossilis Arctica,' Zurich, 1868—1875. For these
and other references to the geological part of my subject I am indebted
to an article on "The Cretaceous Flora," by Professor Morris, 'Popular
Science Review,' 1876, pp. 46—59.
6 Nordenskjold, loc. cit., and Dr. R, H. Scott, 'Geol. Mag.,' February,
1872, p. 71.