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 especially, 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.
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