thus, in the numerous ferns and numerous coniferous trees of the Coal
Measures, known objects by which to conceive of some of the more
prominent features of the flora of which they composed so large a part.
We have not inadequate conceptions of at once the giants of its forests
and the green swathe of its plains and hill-sides,--of its mighty trees
and its dwarf _underwood_,--of its cedars of Lebanon, so to speak, and
its hyssop of the wall. But of an intermediate class we have no
existing representatives; and in this class the fossil botanist finds
puzzles and enigmas with which hitherto at least he has been able to
deal with only indifferent success. There is a view, however,
sufficiently simple, which may be found somewhat to lessen, if not
altogether remove, the difficulty. Nature does not dwell willingly in
mediocrity; and so in all ages she as certainly produced trees, or
plants of tree-like proportions and bulk, as she did minute shrubs and
herbs. In not a few of the existing orders and families, such as the
Rosaceae, the Leguminosae, the Myrtaceae, and many others, we have plants
of all sizes, from the creeping herb, half hidden in the sward, to the
stately tree. The wild dwarf strawberry and minute stone-bramble are of
the same order as our finer orchard trees,--apple, pear, and plum,--or
as those noble hawthorn, mountain ash, and wild cherry trees, that
impart such beauty to our lawns and woods; and the minute spring vetch
and everlasting pea are denizens of the same great family as the tall
locust and rosewood trees, and the gorgeous laburnum. Did there exist no
other plants than the Rosaceae or the Leguminosae, we would possess,
notwithstanding, herbs, shrubs, and trees, just as we do now. And in
plants of a greatly humbler order we have instances of similar variety
in point of size. The humblest grass in our meadows belongs to the same
natural order as the tall bamboo, that, shooting up its panicles amid
the jungles of India to the height of sixty feet, looks down upon all
the second class trees of the country. Again, the minute forked
spleenwort of Arthur Seat, which rarely exceeds three inches in length,
is of the same family as those tree-ferns of New Zealand and Tasmania
that rise to an elevation of from twenty to thirty feet. And we know how
in the ferns provision is made for the attainment and maintenance of the
tree-like size and character. The rachis, which in the smaller species
is either subterranea