332 THE ORIGIN OF SPECIES 



works, this or that plant is often stated to be ill adapted for wide 

 dissemination; but the greater or less facilities for transport 

 across the sea may be said to be almost wholly unknown. Until 

 I tried, with Mr, Berkeley's aid, a few experiments, it was not even 

 known how far seeds could resist the injurious action of sea- 

 water. To my surprise I found that out of eighty-seven kinds, 

 sixty-four germinated after an immersion of twenty-eight days, 

 and a few survived an immersion of 137 days. It deserves notice 

 that certain orders were far more injured than others; nine 

 Leguminosae were tried, and, with one exception, they resisted 

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

 laceae and Polemoniaceae, were all killed by a month's immersion. 

 For convenience sake I chiefly tried small seeds without the cap- 

 sules 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 imme- 

 diately, but when dried they floated for ninety days, and after- 

 ward 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 germinated; the ripe 

 seeds of Helosciadium sunk in two days, when dried they floated 

 for above ninety days, and afterward 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 ff 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 

 experiment) 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 -^ 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 



