pressinum_,--so like a
club moss in its foliage,--belongs; and _Podocarpus ferrugineus_,--a
tree which more closely resembles in its foliage the Eathie conifer,
save that its spiky leaves are somewhat narrower and longer than any
other with which I am acquainted. About two thirds of the plants which
cover the plains, or rise on the hill-sides of that country, are
cryptogamic, consisting mainly of ferns and their allies; and it is a
curious circumstance,--which was, however, not without precedent in the
merely physical conditions of the Oolitic flora of Scotland,--that so
shallow is the soil even where its greatest forests have sprung up, and
so immediately does the rock lie below, that the central axes of the
trees do not elongate downwards into a tap, but throw out horizontally
on every side a thick network of roots, which rises so high over the
surface as to render walking through the woods a difficult and very
fatiguing exercise. The flora of the Oolite, like that of New Zealand,
seems to have been in large part cryptogamic, consisting of ferns and
the allied horse-tail and club moss families. Its forests seem to have
contained only cone-bearing trees; at least among the many thousand
specimens of its fossil woods which have been examined, no tissue of the
true, dicotyledonous character has yet been found; and with the
exception of the leaves just described, all those yet found in the
System, which could have belonged to true trees, are of the acicular
form common to the Coniferae, and show in their dense ligneous structure
that they were persistent, not deciduous. Nor is there evidence wanting
that many of the Coniferae of the period grew in so shallow a soil, that
their tap-roots were flattened and bent backwards, and they were left to
derive their sole support, like the trees of the New Zealand forests,
from such of their roots as shot out horizontally. We even know the
nature of the rock upon which they rested. As shown by fragments still
locked up among the interstices of their petrified roots, it was an Old
Red flagstone similar to that of Caithness in the neighborhood of Wick
and Thurso, and containing the same fossil remains. In the water-rolled
pebbles of the Conglomerate of Helmsdale and Port Gower,--pebbles
encrusted by Oolitic corals, and enclosed in a calcareous paste,
containing Oolitic belemnites and astreae,--I have found the well marked
fishes and fucoids of the Old Red Sandstone. As shown by the appea