s Flora.'
Get all the help you can, if you wish to work the subject out, from
foreign botanists, both European and American; and I think that, on the
whole, you will come to some such theory as this for a general starting
platform. We do not owe our flora--I must keep to the flora just now--to
so many different regions, or types, as Mr. Watson conceives, but to
three, namely: an European or Germanic flora, from the south-east; an
Atlantic flora, from the south-west; a Northern flora from the north.
These three invaded us after the glacial epoch; and our general flora is
their result.

But this will cause you much trouble. Before you go a step further you
will have to eliminate from all your calculations most of the plants
which Watson calls glareal, _i.e_. found in cultivated ground about
habitations. And what their limit may be I think we never shall know.
But of this we may be sure; that just as invading armies always bring
with them, in forage or otherwise, some plants from their own
country--just as the Cossacks, in 1815, brought more than one Russian
plant through Germany into France--just as you have already a crop of
North German plants upon the battle-fields of France--thus 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