h Wenham Lake ice is packed for transport. The Canadian river-weed
is known first to have escaped from the botanical gardens at Cambridge,
whence it spread rapidly through the congenial dykes and sluices of the
fen country, and so into the entire navigable network of the Midland
counties. But there are other aliens of older settlement amongst us,
aliens of American origin which nevertheless arrived in Britain, in all
probability, long before Columbus ever set foot on the low basking
sandbank of Cat Island. Such is the jointed pond-sedge of the Hebrides,
a water-weed found abundantly in the lakes and tarns of the Isle of
Skye, Mull and Coll, and the west coast of Ireland, but occurring
nowhere else throughout the whole expanse of Europe or Asia. How did it
get there? Clearly its seeds were either washed by the waves or carried
by birds, and thus deposited on the nearest European shores to America.
But if Mr. Alfred Russel Wallace had been alive in pre-Columban days
(which, as Euclid remarks, is absurd), he would readily have inferred,
from the frequent occurrence of such unknown plants along the western
verge of Britain, that a great continent lay unexplored to the westward,
and would promptly have proceeded to discover and annex it. As Mr.
Wallace was not yet born, however, Columbus took a mean advantage over
him, and discovered it first by mere right of primogeniture.

In other cases, the circumstances under which a particular plant appears
in England are often very suspicious. Take the instance of the
belladonna, or deadly nightshade, an extremely rare British species,
found only in the immediate neighbourhood of old castles and monastic
buildings. Belladonna, of course, is a deadly poison, and was much used
in the half-magical, half-criminal sorceries of the Middle Ages. Did you
wish to remove a troublesome rival or an elder brother, you treated him
to a dose of deadly nightshade. Yet why should it, in company with many
other poisonous exotics, be found so frequently around the ruins of
monasteries? Did the holy fathers--but no, the thought is too
irreverent. Let us keep our illusions, and forget the friar and the
apothecary in 'Romeo and Juliet.'

Belladonna has never fairly taken root in English soil. It remains, like
the Roman snail and the Portuguese slug, a mere casual straggler about
its ancient haunts. But there are other plants which have fairly
established their claim to be considered as native-born Britons,