GEOGRAPHICAL DISTRIBUTION 333 



of sixty miles per diem) ; on this average, the seeds of ^^ plants 

 belonging to one country might be floated across 924 miles of 

 sea to another country, and when stranded, if blown by an in- 

 land gale to a favorable 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 favored 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 -Jf of his seeds 

 of different kinds floated for forty-two days, and were then ca- 

 pable 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 per- 

 haps be safer to assume that the seeds of about ^^ plants of a 

 flora, after having been dried, could be floated across a space of 

 sea 900 miles in width, and would then germinate. The facts of 

 the larger fruits often floating longer than the small, is interest- 

 ing; as plants with large seeds or fruit which, as Alph. de Can- 

 dolle has shown, generally have restricted ranges, could hardly 

 be transported by any other means. 



Seeds may be occasionally transported in another manner. 

 Drift timber is thrown up on most islands, even on those in the 

 midst of the widest oceans; and the natives of the coral islands 

 in the Pacific procure stones for their tools, solely from the roots 

 of drifted trees, these stones being a valuable royal tax. I find 

 that when irregularly shaped stones are embedded in the roots of 

 trees, small parcels of earth are frequently enclosed in their in- 

 terstices and behind them, so perfectly that not a particle could 

 be washed away during the longest transport: out of one small 

 portion of earth thus completely inclosed by the roots of an oak 

 about fifty years old, three dicotyledonous plants germinated: I 

 am certain of the accuracy of this observation. Again, I can show 

 that the carcasses of birds, when floating on the sea sometimes 

 escape being immediately devoured: and many kinds of seeds in 

 the crops of floating birds long retain their vitality: pease and 

 vetches, for instance, are killed by even a few days' immersion in 

 sea-water; but some taken out of the crop of a pigeon, which had 



