be organized must be due to the too great
compression that the carbonized cells and vessels have undergone when yet
soft and elastic, at the time this slow but continuous pressure was being
exerted.

It also became of interest to find out whether, through the very fact of
carbonization, the dimensions of the organic elements had perceptibly
varied--a sort of research that presents certain difficulties. At present
we have no living plant that is comparable, even remotely, with those that
grew during the coal epoch. Moreover, the organic elements have absolutely
nothing constant in their dimensions.

Still, if we limit ourselves to a comparison of the same carbonized wood,
preserved on the one hand by petrifaction, and on the other hand
non-mineralized, we find a very perceptible diminution in bulk. The
elements have contracted in length, breadth, and thickness, but
principally in the direction of the compression that they have undergone
in the purely carbonized specimens.

In the vicinity of the carbonized portions, those of the tracheae that have
not done so have perceptibly preserved their primitive length, which has,
so to speak, been maintained by their neighbors, but their other
dimensions have become much smaller--a quarter in thickness and half in
length.

[Illustration: 12i: FIG. 9.--_Calamodendron,_ Commentry; prosenchymatous
portion of the wood carbonized, X200.]

If the two fragments of the same wood are, one of them silicified and the
other simply carbonized and preserved in sandstone, the diminution in
volume will have occurred in all directions in the latter of the two.

[Illustration: 12j: FIG. 10.--_Calamodendron,_ fragment of the vascular
portion of the wood carbonized.]

Figs. 9 and 11, which represent a portion of the _fibrous_ region of
Calamodendron wood, may give an idea of the shrinkage that has taken place
therein. In Figs. 11 and 12, which show a few tracheae and medullary rays
of the ligneous bands of the same plant, we observe the same phenomenon.
We might cite a large number of analogous examples, but shall be content
to give the following: Figs. 13 and 15 represent radial and tangential
sections of the bark of _Syringodendron pes-caprae_. This is the first time
that one has had before his eyes the anatomical structure of the bark of a
_Syringodendron_, a plant which has not yet been found in a petrified
state. It is coal, then, with its structure preserved, that allows of a
verificati