conifers, which exhibit this structure, have been placed in the same
division.

The familiar fossil known to geologists as _Sternbergia_ has now been
shown to be the cast of the central pith of these conifers, amongst which
may be mentioned _cordaites, araucarites_, and _dadoxylon._. The central
cores had become replaced with inorganic matter after the pith had shrunk
and left the space empty. This shrinkage of the pith is a process which
takes place in many plants even when living, and instances will at once
occur, in which the stems of various species of shrubs when broken open
exhibit the remains of the shrunken pith, in the shape of thin discs
across the interval cavity.

We might reasonably expect that where we find the remains of fossil
coniferous trees, we should also meet with the cones or fruit which they
bear. And such is the case. In some coal-districts fossil fruits, named
_cardiocarpum_ and _trigonocarpum_, have been found in great quantities,
and these have now been decided by botanists to be the fruits of certain
conifers, allied, not to those which bear hard cones, but to those which
bear solitary fleshy fruits. Sir Charles Lyell referred them to a Chinese
genus of the yew tribe called _salisburia_. Dawson states that they are
very similar to both _taxus_ and _salisburia._. They are abundant in some
coal-measures, and are contained, not only in the coal itself, but also
in the sandstones and shales. The under-clays appear to be devoid of
them, and this is, of course, exactly what might have been expected,
since the seeds would remain upon the soil until covered up by vegetable
matter, but would never form part of the clay soil itself.

In connection with the varieties which have been distinguished in the
families of the conifers, calamites, and sigillariae, Sir William Dawson