ir seeds, as some
think, dormant in the ground; or are the seeds which have germinated
fresh ones wafted thither by wind or otherwise, and only able to
germinate in that one spot, because there the soil is clear? General
Monro, now famous for his unequalled memoir on the bamboos, holds to the
latter theory. He pointed out to me that the _Epilobium_ seeds, being
feathered, could travel with the wind; that the plant always made its
appearance first on new banks, landslips, clearings, where it had nothing
to compete against; and that the foxglove did the same. True, and most
painfully true, in the case of thistles and groundsels: but foxglove
seeds, though minute, would hardly be carried by the wind any more than
those of the white clover, which comes up so abundantly in drained fens.
Adhuc sub judice lis est, and I wish some young naturalists would work
carefully at the solution; by experiment, which is the most sure way to
find out anything.

But in researches in this direction they will find puzzles enough. I
will give them one which I shall be most thankful to hear they have
solved within the next seven years--How is it that we find certain
plants, namely, the thrift and the scurvy grass, abundant on the
sea-shore and common on certain mountain-tops, but nowhere between the
two? Answer me that. For I have looked at the fact for years--before,
behind, sideways, upside down, and inside out--and I cannot understand
it.

But all these questions, and specially, I suspect, that last one, ought
to lead the young student up to the great and complex question--How were
these islands re-peopled with plants and animals, after the long and
wholesale catastrophe of the glacial epoch?

I presume you all know, and will agree, that the whole of these islands,
north of the Thames, save certain ice-clad mountain-tops, were buried for
long ages under an icy sea. From whence did vegetable and animal life
crawl back to the land, as it rose again; and cover its mantle of glacial
drift with fresh life and verdure?

Now let me give you a few prolegomena on this matter. You must study the
plants of course, species by species. Take Watson's 'Cybele Britannica,'
and Moore's 'Cybele Hibernica;' and let--as Mr. Matthew Arnold would
say--"your thought play freely about them." Look carefully, too, in the
case of each species, at the note on its distribution, which you will
find appended in Bentham's 'Handbook,' and in Hooker's 'Student'