In Johnston's Physical Atlas, the average rate of
the several Atlantic currents is thirty-three miles per diem (some currents
running at the rate of sixty miles per diem); on this average, the seeds of
14/100 plants belonging to one country might be floated across 924 miles of
sea to another country; and when stranded, if blown by an inland gale to a
favourable spot, would germinate.
Subsequently to my experiments, M. Martens tried similar ones, but in a
much better manner, for he placed the seeds in a box in the actual sea, so
that they were alternately wet and exposed to the air like really floating
plants. He tried ninety-eight seeds, mostly different from mine, but he
chose many large fruits, and likewise seeds, from plants which live near
the sea; and this would have favoured both the average length of their
flotation and their resistance to the injurious action of the salt-water.
On the other hand, he did not previously dry the plants or branches with
the fruit; and this, as we have seen, would have caused some of them to
have floated much longer. The result was that 18/98 of his seeds of
different kinds floated for forty-two days, and were then capable of
germination. But I do not doubt that plants exposed to the waves would
float for a less time than those protected from violent movement as in our
experiments. Therefore, it would perhaps be safer to assume that the seeds
of about 10/100 plants of a flora, after having been dried, could be
floated across a space of sea 900 miles in width, and would then germinate.
Pages:
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608