The living club-mosses are, for the most part, insignificant and
creeping herbs, which, superficially, very closely resemble true mosses,
and none of them reach more than two or three feet in height. But,
in their essential structure, they very closely resemble the earliest
Lepidodendroid trees of the coal: their stems and leaves are similar;
so are their cones; and no less like are the sporangia and spores; while
even in their size, the spores of the _Lepidodendron_ and those of the
existing _Lycopodium_, or club-moss, very closely approach one another.
Thus, the singular conclusion is forced upon us, that the greater and
the smaller sacs of the "Better-Bed" and other coals, in which the
primitive structure is well preserved, are simply the sporangia and
spores of certain plants, many of whicn were closely allied to the
existing club-mosses. And if, as I believe, it can be demonstrated
that ordinary coal Is nothing but "saccular" coal which has undergone a
certain amount of that alteration which, if continued, would convert it
into anthracite; then, the conclusion is obvious, that the great mass
of the coal we burn is the result of the accumulation of the spores
and spore-cases of plants, other parts of which have furnished
the carbonized stems and the mineral charcoal, or have left their
impressions on the surfaces of the layer.