Chap. XII.] WEANS OF DISPERSAL. 325 



immersion. For convenience' sake I chiefly tried small seeds, 

 without the capsule or fruit ; and as all of these sank in a few days, 

 they could not have been floated across wide spaces of the sea, 

 •whether or not they were injured by the salt-water. Afterwards 

 I tried some larger fruits, capsules, &c, 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 94 plants with ripe fruit, and to place them 

 on sea-water. The majority sank quickly, but some which, whilst 

 green, floated for a very short time, when dried floated much longer ; 

 for instance, ripe hazel-nuts sank immediately, but when dried 

 they floated for 90 days, and afterwards when planted germinated ; 

 an asparagus-plant with ripe berries floated for 23 days, when dried 

 it floated for 85 days, and the seeds afterwards germinated ; the 

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

 floated for above 90 days, and afterwards 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 

 f^f- kinds of seeds germinated after an immersion of 28 days ; and 

 as if distinct species with ripe fruit (but not all the same species 

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

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

 these scanty facts, that the seeds of -jL 4 kinds 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 currents is 33 miles per 

 diem (some currents running at the rate of 60 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 inland gale to a favourable 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 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 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 



