are here stated. Now it is clear that a predominance of these forms
in succession marked the successive epochs developed by fossil
geology; the simple abounding first, and the complex afterwards.

Two-thirds of the plants of the carboniferous era are of the cellular
or cryptogamic kind, a proportion which would probably be much
increased if we knew the whole Flora of that era. The ascertained
dicotyledons, or higher-class plants, are comparatively few in this
formation; but it will be found that they constantly increased as the
globe grew older.

The master-form or type of the era was the fern, or breckan, of which
about one hundred and thirty species have already been ascertained as
entering into the composition of coal. {84a} The fern is a plant
which thrives best in warm, shaded, and moist situations. In
tropical countries, where these conditions abound, there are many
more species than in temperate climes, and some of these are
arborescent, or of a tree-like size and luxuriance. {84b} The ferns
of the coal strata have been of this magnitude, and that without
regard to the parts of the earth where they are found. In the coal
of Baffin's Bay, of Newcastle, and of the torrid zone alike, are the
fossil ferns arborescent, shewing clearly that, in that era, the
present tropical temperature, or one even higher, existed in very
high latitudes.

In the swamps and ditches of England there grows a plant called the
horse-tail (equisetum), having a succulent, erect, jointed stem, with
slender leaves, and a scaly catkin at the top. A second large
section of the plants of the carboniferous era were of this kind
(equisetaceae), but, like the fern, reaching the magnitudes of trees.