ructure,
are they mere impressions or are they the plants themselves changed? To
what extent do these agree with coal? What particular plants and what
parts of these appear to have formed coal? Its fibrous structure would
hint at formation from the woody system, and it is not incompatible with
the _deliquescence_ of a thick layer of drift.

The plants of coal fields having been drifted, can only give us an idea
of the vegetation along the natural drains of the then country, such may
by no means have had _one universal character_.

The plants of the open surface of modern tropical countries being
generally different from those along the beds of streams, in which
situations now-a-days Equiseteae, Lycopods and Filicis are chiefly found.
Coal being drift, it follows that the plants of the coal fields can give
us no information on the distribution of vegetables in those days; to
gain information on this, the fossils should be in their original
situation. And there again an obstacle may exist in our not being able
to ascertain the height or level of that situation.

If the plants of coal fields are found to be converted into coal, then
the only difference between coal shale, and coal will consist in the very
small proportion of vegetable matter in the former.

The small number of coal plants, i.e. the small number of species, at
once points to the supposition that fossil plants are confined to those
of the most indestructible nature: here again is another sign of this in
the preponderance of Ferns, which Lindley finds to be the most permanent.

Hence the preponderance of Ferns, is by no means explainable by their
greatest simplicity of form, and consequent priority of formation.

CHAPTER XXII.

_From Peshawur to Lahore_.

_October 14th_.--Peshawur.--Cucurbitaceae. The petals of cucurbita
were observed in one instance united along two of the corollal sinuses to
the staminal column, alternating with the smaller stamina; the processes
were produced upwards into petaloid appendages.

_17th_.--Proceeded to Nowshera. As far as Pubbe the road extended
chiefly through a cultivated country, thence as far as could be judged at
night, over a plain country covered with coarse grass, and here and there
(whenever a sufficiently gravelly surface occurred) among the thick of
_Bheir_, which is here used for fences; Mudar, AErua, Nerioides and
Adhatoda occurred; _Furas_ a common tree.

_18th_.--Reached Khairabad. The sa