The Story of a Piece of Coal | Page 7

Their appearance
can be called to mind by imagining the cylindrical fruit of the maize or
Indian corn to be reduced to some three or four inches in length. The
sporangia or cases which contained the microscopic spores or seeds
were arranged around a central axis in a somewhat similar manner to
that in which maize is found. These bodies have since been found
actually situated at the end of branches of _lepidodendron_, thus
placing their true nature beyond a doubt. The fossil seeds (spores) do
not appear to have exceeded in volume those of recent club-mosses,
and this although the actual trees themselves grew to a size very many
times greater than the living species. This minuteness of the seed-germs
goes to explain the reason why, as Sir Charles Lyell remarked, the
same species of lepidodendra are so widely distributed in the coal
measures of Europe and America, their spores being capable of an easy
transportation by the wind.
[Illustration: FIG. 14.--_Lepidostrobus._ Coal-shale.]
One striking feature in connection with the fruit of the lepidodendron
and other ancient representatives of the club-moss tribe, is that the
bituminous coals in many, if not in most, instances, are made up almost
entirely of their spores and spore-cases. Under a microscope, a piece of
such coal is seen to be thronged with the minute rounded bodies of the
spores interlacing one another and forming almost the whole mass,
whilst larger than these, and often indeed enclosing them, are flattened
bag-like bodies which are none other than the compressed sporangia
which contained the former.
[Illustration: FIG. 15.--Lycopodites. Coal sandstone.]
Now, the little Scottish or Alpine club-moss which is so familiar,
produces its own little cones, each with its series of outside scales or
leaves; these are attached to the bags or spore-cases, which are crowded
with spores. Although in miniature, yet it produces its fruit in just the
same way, at the terminations of its little branches, and the spores, the
actual germs of life, when examined microscopically, are scarcely
distinguishable from those which are contained in certain bituminous

coals. And, although ancient club-mosses have been found in a
fossilised condition at least forty-nine feet high, the spores are no larger
than those of our miniature club-mosses of the present day.
The spores are more or less composed of pure bitumen, and the
bituminous nature of the coal depends largely on the presence or
absence of these microscopic bodies in it. The spores of the living
club-mosses contain so much resinous matter that they are now largely
used in the making of fireworks, and upon the presence of this altered
resinous matter in coal depends its capability of providing a good
blazing coal.
At first sight it seems almost impossible that such a minute cause
should result in the formation of huge masses of coal, such an
inconceivable number of spores being necessary to make even the
smallest fragment of coal. But if we look at the cloud of spores that can
be shaken from a single spike of a club-moss, then imagine this to be
repeated a thousand times from each branch of a fairly tall tree, and
then finally picture a whole forest of such trees shedding in due season
their copious showers of spores to earth, we shall perhaps be less
amazed than we were at first thought, at the stupendous result wrought
out by so minute an object.
Another well-known form of carboniferous vegetation is that known as
the _Sigillaria_, and, connected with this form is one, which was long
familiar under the name of _Stigmaria_, but which has since been
satisfactorily proved to have formed the branching root of the sigillaria.
The older geologists were in the habit of placing these plants among the
tree-ferns, principally on account of the cicatrices which were left at the
junctions of the leaf-stalks with the stem, after the former had fallen off.
No foliage had, however, been met with which was actually attached to
the plants, and hence, when it was discovered that some of them had
long attenuated leaves not at all like those possessed by ferns,
geologists were compelled to abandon this classification of them, and
even now no satisfactory reference to existing orders of them has been
made, owing to their anomalous structure. The stems are fluted from
base to stem, although this is not so apparent near the base, whilst the

raised prominences which now form the cicatrices, are arranged at
regular distances within the vertical grooves.
When they have remained standing for some length of time, and the
strata have been allowed quietly to accumulate around the trunks, they
have escaped compression. They were evidently, to a great extent,
hollow like a reed, so that in those trees which still remain vertical, the
interior has become filled up by