Orkney, most remained to be
done; and his collection of these is the most considerable in the number
of its specimens that I have yet seen. It, however, serves but to show
how very extreme is the poverty of the flora of the Lower Old Red
Sandstone. The numerous fishes of the period seem to have inhabited a
sea little more various in its vegetation than in its molluscs. Among
the specimens of Mr. Clouston's collection I could detect but two
species of plants,--an imperfectly preserved vegetable, more nearly
resembling a club-moss than aught I have seen, and a smooth-stemmed
fucoid, existing as a mere coaly film on the stone, and distinguished
chiefly from the other by its sharp-edged, well-defined outline, and
from the circumstance that its stems continue to retain the same
diameter for a considerable distance, and this, too, after throwing off
at acute angles numerous branches, nearly equal in bulk to the parent
trunk. In a specimen about two and a half feet in length, which I owe to
the kindness of Mr. Dick of Thurso, there are stems continuous
throughout, that, though they ramify into from six to eight branches in
that space, are quite as thick atop as at bottom. They are the remains,
in all probability, of a long flexible fucoid, like those fucoids of the
intertropical seas that, streaming slantwise in the tide, rise not
unfrequently to the surface in fifteen and twenty fathoms water. I saw
among Mr. Clouston's specimens no such lignite as the fragment of true
coniferous wood which I had found at Cromarty a few years previous, and
which, it would seem, is still unique among the fossils of the Old Red
Sandstone. In the chart of the Pacific attached to the better editions
of "Cook's Voyages," there are several entries along the track of the
great navigator that indicate where, in mid-ocean, trees, or fragments
of trees, had been picked up. The entries, however, are but few, though
they belong to all the three voyages together: if I remember aright,
there are only five entries in all,--two in the Northern and three in
the Southern Pacific. The floating tree, at a great distance from land,
is of rare occurrence in even the present scene of things, though the
breadth of land be great, and trees numerous; and in the times of the
Old Red Sandstone, when probably the breadth of land was _not_ great,
and trees _not_ numerous, it seems to have been of rarer occurrence
still. But it is at least something to know that in this earl