H.C.
Watson) from their somewhat northern character, in comparison with the
latitude, I suspected that these islands had been partly stocked by
ice-borne seeds during the Glacial epoch. At my request Sir C. Lyell wrote
to M. Hartung to inquire whether he had observed erratic boulders on these
islands, and he answered that he had found large fragments of granite and
other rocks, which do not occur in the archipelago. Hence we may safely
infer that icebergs formerly landed their rocky burdens on the shores of
these mid-ocean islands, and it is at least possible that they may have
brought thither the seeds of northern plants.
Considering that these several means of transport, and that other means,
which without doubt remain to be discovered, have been in action year after
year for tens of thousands of years, it would, I think, be a marvellous
fact if many plants had not thus become widely transported. These means of
transport are sometimes called accidental, but this is not strictly
correct: the currents of the sea are not accidental, nor is the direction
of prevalent gales of wind. It should be observed that scarcely any means
of transport would carry seeds for very great distances; for seeds do not
retain their vitality when exposed for a great length of time to the action
of sea water; nor could they be long carried in the crops or intestines of
birds. These means, however, would suffice for occasional transport across
tracts of sea some hundred miles in breadth, or from island to island, or
from a continent to a neighbouring island, but not from one distant
continent to another.
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