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, howeve