332 MEANS OF DISPERSAL. Chap. XI. 



days, and afterward -wlioii planted tliey cremunatcd ; an aspar- 

 a2:u.s-j)lant with ripe berries floated for ^3 days, when dried it 

 floated for 85 (lays, and the seeds afterward germinated; the 

 ripe seeds of llelosciadimn sank in two days, when dried they 

 floated for above 90 days, and afterward germinated. Alto- 

 gether, out of the 94 clried plants, 18 floated for above '28 

 days, and some of the 18 floated for a very much longer period. 

 So that as -J;^- seeds germinated after an immersion of 28 days ; 

 and as 1} ])lants 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 any thing from these 

 scanty fticts, we may conclude that the seeds of ^^ 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 cur- 

 rents is 33 miles per diem (some currents running at the rate 

 of GO miles per diem) ; on this average, the seeds of -jJ^g- plants 

 belonging to one country might be floated across 924 miles 

 of sea to another country ; and when stranded, if blown to a 

 favorable spot by an inland gale, they Avould 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 fiivored 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 pre^^iously 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 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 

 tliose protected from violent movement as in our experiments. 

 Therefore it would perhaps be safer to assume that the seeds 

 of about -^/g- plants of a flora, after having been dried, could 

 be floated across a space of sea 900 miles in Avidth, and would 

 then germinate. The fact of the larger fruits often floating 

 longer than the small, is interesting ; as plants with large 

 seeds or fruit could hardly be transported by any other means ; 

 and Alph. do Candollo has shown that such plants generally 

 have restricted ranges. 



