CHAP. XII.] MEANS OF DISPERSAL. 305 



injurious action of sea-water. To my surprise I found that out 

 of 87 kinds, 64 germinated after an immersion of 28 days, and a 

 few survived an immersion of 137 days. It deserves notice that 

 certain orders were far more injured than others: nine Legu- 

 minosae were tried, and, with one exception, they resisted the 

 salt-water badly; seven species of the allied orders, Hydro- 

 phyllaceae and Polemoniacese, were all killed by a month's im- 

 mersion. 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. After- 

 wards 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 after- 

 wards 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 {j-f kinds of seeds germinated 

 after an immersion of 28 days; and as ^f distinct species with 

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

 ment) floated, after being dried, for above 28 days, we may con- 

 clude, as far as anything can be inferred from these scanty facts, 

 that the seeds of ^ 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 Y\J^ 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 



