do conquering races bring new plants. The Romans,
during their 300 or 400 years of occupation and civilisation, must
have brought more species, I believe, than I dare mention. I
suspect them of having brought, not merely the common hedge elm of
the south, not merely the three species of nettle, but all our red
poppies, and a great number of the weeds which are common in our
cornfields; and when we add to them the plants which may have been
brought by returning crusaders and pilgrims; by monks from every
part of Europe, by Flemings or other dealers in foreign wool--we
have to cut a huge cantle out of our indigenous flora: only, having
no records, we hardly know where and what to cut out; and can only,
we elder ones, recommend the subject to the notice of the younger
botanists, that they may work it out after our work is done.

Of course these plants introduced by man, if they are cut out, must
be cut out of only one of the floras, namely, the European; for
they, probably, came from the south-east, by whatever means they
came.

That European flora invaded us, I presume, immediately after the
glacial epoch, at a time when France and England were united, and
the German Ocean a mere network of rivers, which emptied into the
deep sea between Scotland and Scandinavia. And here I must add,
that endless questions of interest will arise to those who will
study, not merely the invasion of that truly European flora, but the
invasion of reptiles, insects, and birds, especially birds of
passage, which must have followed it as soon as the land was
sufficiently covered with vegetation to support life. Whole volumes
remain to be written on this subject. I trust that some of your
younger members may live to write one of them. The way to begin
will be; to compare the flora and fauna of this part of England very
carefully with that of the southern and eastern counties; and then
to compare them again with the fauna and flora of France, Belgium,
and Holland.

As for the Atlantic flora, you will have to decide for yourselves
whether you accept or not the theory of a sunken Atlantic continent.
I confess that all objections to that theory, however astounding it
may seem, are outweighed in my mind by a host of facts which I can
explain by no other theory. But you must judge for yourselves; and
to do so you must study carefully the distribution of heaths both in
Europe and at the Cape, and their non-appearance beyond the Ural
Mounta