I must now say a few words on what are called accidental means, but which more properly might be called occasional means of distribution.  I shall here confine myself to plants.  In botanical works, this or that plant is stated to be ill adapted for wide dissemination; but for transport across the sea, the greater or less facilities 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 87 kinds, 64 germinated after an immersion of 28 days, and a few survived an immersion of 137 days.  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 be floated across wide spaces of the sea, whether or not they were injured by the salt-water.  Afterwards 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 might wash down plants or branches, and that these might be dried on the banks, and then by a fresh rise in the stream be washed into the sea.  Hence I was led to dry 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 they 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 64/87 seeds germinated after an immersion of 28 days; and as 18/94 plants 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 anything from these scanty facts, we may conclude that the seeds of 14/100 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 14/100 plants belonging to one country might be floated across 924 miles of sea to another country; and when stranded, if blown to a favourable spot by an inland gale, they would germinate.