306 MEANS OF DISPERSAL. [CHAP. XII. 



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 |,| of his seeds 

 of different kinds floated for 42 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 ffo 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 fact 

 of the larger fruits often floating longer than the small, is inter- 

 esting ; as plants with large seeds or fruit which, as Alph. de 

 Candolle 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 threwn 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 inter- 

 stices 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 cvnipletely enclosed by the roots of an oak 

 about 50 years old, three dicotyledonous plants germinated : I am 

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

 that the carcases 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: peas 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 

 floated on artificial sea- water for 30 days, to my surprise nearly 

 all germinated. 



Living birds can hardly fail to be highly effective agents in the 

 transportation of seeds. I could give many facts showing how 

 frequently birds of many kinds are blown by gales to vast dis- 

 tances across the ocean. We may safely assume that under such 

 circumstances their rate of flight would often be 35 miles an hour ; 

 and some authors have given a far higher estimate. I have never 

 seen an instance of nutritious seeds passing through the intestines 

 of a bird ; but hard seeds of fruit pass uninjured through even 

 the digestive organs of a turkey. In the course of two months, I 

 picked up in my garden 12 kinds of seeds, out of the excrement 



