age.
Sixty-five species of plants have been identified, of which there are
fifteen ferns, two cycads, eleven coniferae, three monocotyledons, and
thirty-four dicotyledons. One of the ferns is a tree-fern with thick stems,
which has also been found in the Upper Greensand of England. Among the
conifers the giant sequoias are found, and among {75} the dicotyledons the
genera Populus, Myrica, Ficus, Sassafras, Andromeda, Diospyros, Myrsine,
Panax, as well as magnolias, myrtles, and leguminosae. Several of these
groups occur also in the much richer deposits of the same age in North
America and Central Europe; but all of them evidently afford such
fragmentary records of the actual flora of the period, that it is
impossible to say that any genus found in one locality was absent from the
other merely because it has not yet been found there. On the whole, there
seems to be less difference between the floras of Arctic and temperate
latitudes in Upper Cretaceous than in Miocene times.

In the same locality in Greenland (70deg 33' N. Lat. and 52deg W. Long.),
and also in Spitzbergen, a more ancient flora, of Lower Cretaceous age, has
been found; but it differs widely from the other in the great abundance of
cycads and conifers and the scarcity of exogens, which latter are
represented by a single poplar. Of the thirty-eight ferns, fifteen belong
to the genus Gleichenia now almost entirely tropical. There are four genera
of cycads, and three extinct genera of conifers, besides Glyptostrobus and
Torreya now found only in China and California, six species of true pines,
and five of the genus Sequoia, one of which occurs also in Spitzbergen. The
European deposits of the same age closely agree with these in their general
character, conifers, cycads, and ferns forming the mass of the vegetation,
while exogens are entirely absent, the above-named Greenland poplar being
the oldest known dicotyledonous plant.[17]

If we take these facts as really representing the flora of the period, we
shall be forced to conclude that, measured by the change effected in its
plants, the lapse of time between the Lower and Upper Cretaceous deposits
was far greater than between the Upper Cretaceous and the Miocene--a
conclusion quite opposed to the indications afforded by the mollusca and
the higher animals of the two periods. It seems probable, therefore, that
these Lower Cretaceous plants represent local peculiarities of {76}
vegetation such as now sometime