This terrestrial period is characterised, in a remarkable manner, by the
abundance and strangeness of the vegetation which then covered the
islands and continents of the whole globe. Upon all points of the earth,
as we have said, this flora presented a striking uniformity. In
comparing it with the vegetation of the present day, the learned French
botanist, M. Brongniart, who has given particular attention to the flora
of the Coal-measures, has arrived at the conclusion that it presented
considerable analogy with that of the islands of the equatorial and
torrid zone, in which a maritime climate and elevated temperature exist
in the highest degree. It is believed that islands were very numerous at
this period; that, in short, the dry land formed a sort of vast
archipelago upon the general ocean, of no great depth, the islands being
connected together and formed into continents as they gradually emerged
from the ocean.
This flora, then, consists of great trees, and also of many smaller
plants, which would form a close, thick turf, or sod, when partially
buried in marshes of almost unlimited extent. M. Brongniart indicates,
as characterising the period, 500 species of plants belonging to
families which we have already seen making their first appearance in the
Devonian period, but which now attain a prodigious development. The
ordinary dicotyledons and monocotyledons--that is, plants having seeds
with two lobes in germinating, and plants having one seed-lobe--are
almost entirely absent; the cryptogamic, or flowerless plants,
predominate; especially Ferns, Lycopodiaceæ and Equisetaceæ--but of
forms insulated and actually extinct in these same families. A few
dicotyledonous gymnosperms, or naked-seed plants forming genera of
Conifers, have completely disappeared, not only from the present flora,
but since the close of the period under consideration, there being no
trace of them in the succeeding Permian flora. Such is a general view of
the features most characteristic of the Coal period, and of the Primary
epoch in general. It differs, altogether and absolutely, from that of
the present day; the climatic condition of these remote ages of the
globe, however, enables us to comprehend the characteristics which
distinguish its vegetation. A damp atmosphere, of an equable rather than
an intense heat like that of the tropics, a soft light veiled by
permanent fogs, were favourable to the growth of this peculiar
vegetation, of which we search in vain for anything strictly analogous
in our own days. The nearest approach to the climate and vegetation
proper to the geological period which now occupies our attention, would
probably be found in certain islands, or on the littoral of the Pacific
Ocean--the island of Chloë, for example, where it rains during 300 days
in the year, and where the light of the sun is shut out by perpetual
fogs; where arborescent Ferns form forests, beneath whose shade grow
herbaceous Ferns, which rise three feet and upwards above a marshy soil;
which gives shelter also to a mass of cryptogamic plants, greatly
resembling, in its main features, the flora of the Coal-measures. This
flora was, as we have said, uniform and poor in its botanic genera,
compared to the abundance and variety of the flora of the present time;
but the few families of plants, which existed then, included many more
species than are now produced in the same countries. The fossil Ferns of
the coal-series in Europe, for instance, comprehend about 300 species,
while all Europe now only produces fifty. The gymnosperms, which now
muster only twenty-five species in Europe, then numbered more than 120.
It will simplify the classification of the flora of the Carboniferous
epoch if we give a tabular arrangement adopted by the best
authorities:--
Dr. Lindley. Brongniart.
I. Thallogens { Cryptogamous Amphigens, } Lichens, Sea-weeds, Fungi.
{ or Cellular Cryptogams }
II. Acrogens Cryptogamous Acrogens { Club-mosses, Equiseta, Ferns,
{ Lycopods, Lepidodendra.