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As you have done me the honour to notice favourably my wish to ascertain
experimentally the power of resistance in seeds to the injurious action of
seawater, you may perhaps like to have a report. As such experiments might
naturally appear childish to many. I may be permitted to premise that they
have a direct bearing on a very interesting problem. which has lately,
especially in America. attracted much attention, namely, whether the same
organic being has been created at one point or on severa1 on the face of
our globe. As geologist I feel a special interest on the possibility of
plants being transported by sea to distant islands, owing to the great
influence which it is very obvious the views of the late ever-lamented
Edward Forbes² have had on the subsequent writings of botanists and
zoologists. Forbes, as is well known, boldly supposed that the north coast
of Spain had formerly been directly continuous with Ireland. and he extended
the continent of Europe as far as and beyond the Azores. To imagine such
enormous geological changes within the period of the existence of now living
beings, on no other ground but to account for their distribution, seems to me,
in our present state of ignorance on the means of transportal. an almost
retrograde step in science -- it cuts the knot instead of untying it. Weighty
objections might, I think, be urged against Forbes' hypothesis as applied
in the above and many other cases, but this is not the proper place to
discuss such a question. As I had not the least notion when I began, whether
or not the seeds would be all killed by a single week's immersion, I at first
took only a few, selecting them almost by chance from the different great
natural families: but I am now trying a set chosen on philosophical
principles by the kindness of Dr. Hooker.
The sea-water has been made artificially with salt procured from Mr.
Bolton, 146, Holborn Bars, which has been tested by better chemists than
men namely, by numerous sea animals and algae having lived in it for more
than a year. The seeds were placed in separate bottles holding from 2 oz
to 4 oz each, out of doors in the shade: the mean temperature has during
the period been about 44°, rising during one week to a mean of nearly 48°.
Most of the seeds swelled in the water. and some of them slightly coloured
it, and each kind gave to it its own peculiar and strong odour. The water
in which the Cabbage and Radish seeds were placed became putrid and
smelt offensively in a quite extraordinary degree; and it is surprising
that any seeds, as was the case with the Radish, could have resisted so
contaminating an influence; as the water became putrid before I had thought
of this contingency, it was not, and has never been, renewed. I also
placed seeds in a quart bottle in a tank filled with snow and water to
ascertain whether the seeds kept at the temperature of 32° would better
resist the salt water; this water, like that in the small bottle to my
surprise became turbid and smelt rather offensively. In the following list
I have no reason to suppose, except in the cases where so stated that the
seeds have endured their full time.
(1) Seeds of common Cress (Lepidium sativum) have germinated well after
42 days immersion: the give out a surprisingly quantity of slime so as to
cohere in a mass. (2) Radishes have germinated less well after the same
period. (3) Cabbage seed: after 14 days' immersion only one seed out of
many came up: I think this is rather strange considering that the Cabbage
is a sea-side plant: in the ice-cold salt water however, several have
come up after 30 days immersion. (4} Lettuce seed has grown well after
42 days; (3) of Onion seed only a few have germinated after the same period;
(6) Carrot and (7) Celery seed welt after the 42 days; (8) Borago
officinalis. (9) Capsicum (10) Cucurbita ovifera. have germinated well
after the 28 days of immersion: the two latter, rather tender kinds, were
a1so tried in the ice-cold water. and have generated after 30 days
immersion. (11) Savory or Satureja, has grown somewhat less well after 28
days (12) Linum usitatissimum: only one seed out of a mass of seeds (which
gave out much slime) came up after the 28 days and the same thing happened
after 14 days; and only three seeds came tip after the first seven days'
immersion, yet the seed was very good. (13) Rhubarb, (14) Beet, (is) Oracle,
or Atriplex, (16) Oats, (17) Barley. (18) Phalaris canariensis, have all
germinated excellently after 28 days; likewise the six latter after 30 days
in the ice-cold water. (19) Beans and (20) Furze, or Ulex: of these a few
survived with difficulty 14 days; the Beans were all killed by 30 days in
the ice-cold water. (21) Peas germinated after seven days but were all dead
after 14 days' immersion out of doors, and likewise after 30 days in the
ice-cold water. (22) Trifoliurn incarnatum is the only plant of which every
seed has been killed by seven days' immersion; nor did it withstand 30 days
in the ice-cold salt water. (23) Kidney Beans have been tried only in the
latter water, and all were dead after the 30 days.
As out of these 23 kinds of seed, selected almost at hap-hazard, the
five Leguminosae alone have as yet been killed (with the exception of
the Cabbage seed, and these have survived in the ice-cold water) one is
tempted to infer that the seeds of this faintly must generally withstand
salt water much worse than the seeds of the other great natural families;
yet from remarks in botanical works, I had expected that these would have
survived longest. It has been really curious to observe how uniform, even
to a day, the germination has been in almost every kind of seed, when taken
week after week out of the salt water, and likewise when compared with the
same seeds not salted-all of course having been grown under the same
circumstances. namely in glasses on my chimney-piece so, that the seeds
from the day of being planted have been always under my eye. The germination
of the Rhubarb and Celery alone has been in a marked degree altered, having
been accelerated. With respect to Convolvulus tricolor, not included in the
above list, I may mention that many of the seeds germinated and came out of
their husks, whilst still in the salt water, after six or seven days'
immersion.
To return to the subject of transportal, I may state that in "Johnston's
Physical Atlas"³ the rates of 10 distinct currents in the Atlantic
(excluding drift currents) are given, and the average of them is 33
nautical miles per diem; hence in 42 days which length of immersion seven
out of the eight kind, of seed as yet tested have already stood, a seed
might be readily carried between 1300 and 1400 miles.
I will conclude this too lengthy communication by observing that all
the 40-50 seeds which I have as yet tried sink in sea-water: this seems
at first a fatal obstacle to the dissemination of plants by sea currents;
but it may be doubted whether most seeds (with the exception of the winged
kinds), when once shed. are so likely to get washed into the sea as are
whole or nearly whole plants with their fruit by being carried down rivers
during. floods, by water-spouts, whirlwinds, slips of river-cliffs, &
c., continued during the long lapse of geologically modern ages. It should
be borne in mind how beautifully pods capsules, & c. -- and even the
fully expanded heads of the Compositae close when wetted, as if for the
very purpose of carrying the seed safe to land. When landed high up by
the tides and waves, and perhaps driven a little inland by the first
inshore gale the pods, & c. will dry, and opening will shed their
seed; and these will then be ready for all the many means of dispersal
by which Nature sows her broad fields, and which have excited the
admiration of every observer. But when the seed is sown in its new home
then, as I believe, comes the ordeal; will the old occupants in the great
struggle for life allow the new and solitary immigrant room and sustenance?
1 Gardeners Chronicle and Agricultural Gazette no. 21
26 May 1855, pp. -57.
2 Edward Forbes. See, for example. "On Some Indications of
the Molluecous Fauna of the Azores and St. Helena," Report of the
Twenty-first Meeting of the British Association for Advancement of
Science; Held at Ipswitch in July 1851 20(1852):197-99; "On the Extinct
Landshells of St. Helena," Quarterly Journal of the Geological Society
of London"(1852):197-99 and "On the Manifestation of Polarity in the
Distribution of Organized Beings in Time," Edinburgh New Philosophical
Journal 57(1854):332-37.
3 Alexander Keith Johnston. The Physical Atlas; A Series of
Maps & Illustrations of the Geographical Distribution of Natural
Phenomena Embracing: I. Geology. II Hydrography. III. Meteorology. IV.
Natural History. (Edinburgh and London: Blackwood I&5O).
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