Part 12 (1/2)

Dr. Lindley. Brongniart.

I. Thallogens { Cryptogamous Amphigens, } Lichens, Sea-weeds, Fungi.

{ or Cellular Cryptogams }

II. Acrogens Cryptogamous Acrogens { Club-mosses, Equiseta, Ferns, { Lycopods, Lepidodendra.

III. Gymnogens Dicotyledonous Gymnosperms Conifers and Cycads.

{ Compositae, Leguminosae, Umbel- IV. Exogens Dicotyledonous Angiosperms { liferae, Cruciferae, Heaths.

{ All European except Conifers.

V. Endogens Monocotyledons { Palms, Lilies, Aloes, Rushes, { Gra.s.ses.

Calamites are among the most abundant fossil plants of the Carboniferous period, and occur also in the Devonian. They are preserved as striated, jointed, cylindrical, or compressed stems, with fluted channels or furrows at their sides, and sometimes surrounded by a bituminous coating, the remains of a cortical integument. They were originally hollow, but the cavity is usually filled up with a substance into which they themselves have been converted. They were divided into joints or segments, and when broken across at their articulations they show a number of striae, originating in the furrows of the sides, and turning inwards towards the centre of the stem. It is not known whether this structure was connected with an imperfect diaphragm stretched across the hollow of the stem at each joint, or merely represented the ends of woody plates of which the solid part of the stem is composed. Their extremities have been discovered to taper gradually to a point, as represented in _C. cannaeformis_ (Fig. 64), or to end abruptly, the intervals becoming shorter and smaller. The obtuse point is now found to be the root. Calamites are regarded as Equisetaceous plants; later botanists consider that they belong to an extinct family of plants.

_Sigillariae_ are the most abundant of all plants in the coal formation, and were those princ.i.p.ally concerned in the acc.u.mulation of the mineral fuel of the Coal-measures. Not a mine is opened, nor a heap of shale thrown out, but there occur fragments of its stem, marked externally with small rounded impressions, and in the centre slight tubercles, with a quincuncial arrangement. From the tubercles arise long ribbon-shaped bodies, which have been traced in some instances to the length of twenty feet.

[Ill.u.s.tration: Fig. 63.--Sphenophyllum restored.]

In the family of the Sigillarias we have already presented the bark of _S. laevigata_, at page 138; on page 157 we give a drawing of the bark of _S. reniformis_, one-third the natural size (Fig. 65).

In the family of the Asterophyllites, the leaf of _A. foliosa_ (Fig.

66); and the foliage of _Annularia orifolia_ (Fig. 67) are remarkable.

In addition to these, we present, in Fig. 63, a restoration of one of these Asterophyllites, the _Sphenophyllum_, after M. Eugene Deslongchamps. This herbaceous tree, like the Calamites, would present the appearance of an immense asparagus, twenty-five to thirty feet high.

It is represented here with its branches and _fronds_, which bear some resemblance to the leaves of the ginkgo. The bud, as represented in the figure, is terminal, and not axillary, as in some of the Calamites.

[Ill.u.s.tration: Fig. 64.--Calamites cannaeformis. One-third natural size.]

If, during the Coal-period, the vegetable kingdom had reached its maximum, the animal kingdom, on the contrary, was poorly represented.

Some remains have been found, both in America and Germany, consisting of portions of the skeleton and the impressions of the footsteps of a Reptile, which has received the name of Archegosaurus. In Fig. 68 is represented the head and neck of _Archegosaurus minor_, found in 1847 in the coal-basin of Saarbruck between Strasbourg and Treves. Among the animals of this period we find a few Fishes, a.n.a.logous to those of the Devonian formation. These are the _Holoptychius_ and _Megalichthys_, having jaw-bones armed with enormous teeth. Scales of _Pygopterus_ have been found in the Northumberland Coal-shale at Newsham Colliery, and also in the Staffords.h.i.+re Coal-shale. Some winged insects would probably join this slender group of living beings. It may then be said with truth that the immense forests and marshy plains, crowded with trees, shrubs, and herbaceous plants, which formed on the innumerable isles of the period a thick and tufted sward, were almost dest.i.tute of animals.

[Ill.u.s.tration: XI.--Ideal view of a marshy forest of the Coal Period.]

[Ill.u.s.tration: Fig. 65.--Sigillaria reniformis.]

[Ill.u.s.tration: Fig. 66.--Asterophyllites foliosa.]

On the opposite page (PL. XI.) M. Riou has attempted, under the directions of M. Deslongchamps, to reproduce the aspect of Nature during the period. A marsh and forest of the Coal-period are here represented, with a short and thick vegetation, a sort of gra.s.s composed of herbaceous Fern and mare's-tail. Several trees of forest-height raise their heads above this lacustrine vegetation.

On the left are seen the naked trunk of a _Lepidodendron_ and a _Sigillaria_, an arborescent Fern rising between the two trunks. At the foot of these great trees an herbaceous Fern and a _Stigmaria_ appear, whose long ramification of roots, provided with reproductive spores, extend to the water. On the right is the naked trunk of another _Sigillaria_, a tree whose foliage is altogether unknown, a _Sphenophyllum_, and a _Conifer_. It is difficult to describe with precision the species of this last family, the impressions of which are, nevertheless, very abundant in the Coal-measures.

[Ill.u.s.tration: Fig. 67.--Annularia orifolia.]

[Ill.u.s.tration: Fig. 68.--Head and neck of Archegosaurus minor.]

In front of this group we see two trunks broken and overthrown. These are a _Lepidodendron_ and _Sigillaria_, mingling with a heap of vegetable debris in course of decomposition, from which a rich humus will be formed, upon which new generations of plants will soon develop themselves. Some herbaceous Ferns and buds of _Calamites_ rise out of the waters of the marsh.

A few Fishes belonging to the period swim on the surface of the water, and the aquatic reptile _Archegosaurus_ shows its long and pointed head--the only part of the animal which has. .h.i.therto been discovered (Fig. 68). A _Stigmaria_ extends its roots into the water, and the pretty _Asterophyllites_, with its finely-cut stems, rises above it in the foreground.

A forest, composed of _Lepidodendra_ and _Calamites_, forms the background to the picture.