GEOGRAPHICAL DISTRIBUTION 323 



longer ; for instance, ripe hazel-nuts sank immediately, 

 but when dried they floated for 90 days, and afterwards 

 when planted they germinated ; an asparagus plant 

 with ripe berries floated for 23 days, when dried it 

 floated for 85 days, and the seeds afterwards germin- 

 ated ; the ripe seeds of Helosciadium sank in two days, 

 when dried they floated for above 90 days, and after- 

 wards germinated. Altogether out of the 94 dried 

 plants, 18 floated for above 28 days, and some of the 

 18 floated for a very much longer period. So that as |4 

 seeds germinated after an immersion of 28 days ; and 

 as $-£ plants with ripe fruit (but not all the same species 

 as in the foregoing experiment) floated, after being dried, 

 for above 28 days, as far as we may infer anything from 

 these scanty facts, we may conclude that the seeds of 

 tVj- plants of any country might be floated by sea- 

 currents during 28 days, and would retain their power of 

 germination. In Johnston's Physical Atlas, the average 

 rate of the several Atlantic currents is 33 miles per 

 diem (some currents running at the rate of 60 miles 

 per diem) ; on this average, the seeds of -rVir plants 

 belonging to one country might be floated across 924 

 miles of sea to another country ; and when stranded, if 

 blown to a favourable spot by an inland gale, they 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 98 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 the average length of their flota- 

 tion and of 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 frf of his 

 seeds floated for 42 days, and were then capable of 

 germination. But I do not doubt that plants exposed 



