360 MfiANS OF DISPERSAL. 



of the allied orders, Hydrophyllaceae and Polemoniacese, 

 were all killed by a month's immersion. For convenience 

 sake I chiefly tried small seeds without the capsules or 

 fruit ; and as all of these sunk in a few days, they could 

 not have been floated across wide spaces of the sea, whether 

 or not they were injured by salt water. Afterward I tried 

 some larger fruits, capsules, etc., and some of these floated 

 for a long time. It is well known what a difference there 

 is in the buoyancy of green and seasoned timber; and it 

 occurred to me that floods would often wash into the sea 

 dried plants or branches with seed-capsules or fruit attached 

 to them. Hence I was led to dry the stems and branches 

 of ninety-four plants with ripe fruit, and to place them on 

 sea-water. The majority sunk quickly, but some which, 

 while green, floated, for a very short time, when dried, 

 floated much longer ; for instance, ripe hazel-nuts sunk 

 immediately, but when dried they floated for ninety days, 

 and afterward when planted germinated ; an asparagus plant 

 with ripe berries floated for twenty-three days, when dried 

 it floated for eighty-five days, and the seeds afterward ger- 

 minated ; the ripe seeds of Helosciadium sunk in two days, 

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

 ward germinated. Altogether, out of the ninety-four dried 

 plants, eighteen floated for above twenty-eight days; and 

 some of the eighteen floated for a very much longer period. 

 So that as f f kinds of seeds germinated after an immersion 

 of twenty-eight days ; and as || distinct species with ripe 

 fruit (but not all the same species as in the foregoing ex- 

 periment) floated, after being dried, for above twenty-eight 

 days, we may conclude, as far as anything can be inferred 

 from these scanty facts, that the seeds of -j 1 ^ kinds of 

 plants of any country might be floated by sea-currents 

 during twenty-eight days, and would retain their power of 

 germination. 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 -^^ plants belong- 

 ing 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 favorable spot, would germinate. 



Subsequently to my experiments, M. Martens tried simi- 

 lar ones, but in a much better manner, for he placed the 

 seeds in a box in the actual sea, so that they were alter 

 nately wet and exposed to the air like really floating plants. 



