IN THE VEGETABLE KINGDOM.'
1876.
[This book, as pointed out in the 'Autobiography,' is a complement to
the 'Fertilisation of Orchids,' because it shows how important are
the results of cross-fertilisation which are ensured by the mechanisms
described in that book.
By proving that the offspring of cross-fertilisation are more
vigorous than the offspring of self-fertilisation, he showed that one
circumstance which influences the fate of young plants in the
struggle for life is the degree to which their parents are fitted for
cross-fertilisation. He thus convinced himself that the intensity of the
struggle (which he had elsewhere shown to exist among young plants) is
a measure of the strength of a selective agency perpetually sifting
out every modification in the structure of flowers which can effect its
capabilities for cros-fertilisation.
The book is also valuable in another respect, because it throws light on
the difficult problems of the origin of sexuality. The increased vigour
resulting from cross-fertilisation is allied in the closest manner to
the advantage gained by change of conditions. So strongly is this the
case, that in some instances cross-fertilisation gives no advantage to
the offspring, unless the parents have lived under slightly different
conditions. So that the really important thing is not that two
individuals of different BLOOD shall unite, but two individuals which
have been subjected to different conditions. We are thus led to believe
that sexuality is a means for infusing vigour into the offspring by the
coalescence of differentiated elements, an advantage which could not
follow if reproductions were entirely asexual.
It is remarkable that this book, the result of eleven years of
experimental work, owed its origin to a chance observation. My father
had raised two beds of Linaria vulgaris--one set being the offspring of
cross- and the other of self-fertilisation. These plants were grown for
the sake of some observations on inheritance, and not with any view to
cross-breeding, and he was astonished to observe that the offspring of
self-fertilisation were clearly less vigorous than the others. It seemed
incredible to him that this result could be due to a single act of
self-fertilisation, and it was only in the following year when precisely
the same result occurred in the case of a similar experiment on
inheritance in Carnations, that his attention was "thoroughly aroused"
and that he determined to make a series of experiments specially
directed to the question. The following letters give some account of the
work in question.]
CHARLES DARWIN TO ASA GRAY. September 10, [1866?].
... I have just begun a large course of experiments on the germination
of the seed, and on the growth of the young plants when raised from a
pistil fertilised by pollen from the same flower, and from pollen from
a distinct plant of the same, or of some other variety. I have not
made sufficient experiments to judge certainly, but in some cases the
difference in the growth of the young plants is highly remarkable. I
have taken every kind of precaution in getting seed from the same
plant, in germinating the seed on my own chimney-piece, in planting the
seedlings in the same flower-pot, and under this similar treatment I
have seen the young seedlings from the crossed seed exactly twice as
tall as the seedlings from the sel-fertilised seed; both seeds having
germinated on the same day. If I can establish this fact (but perhaps it
will all go to the dogs), in some fifty cases, with plants of different
orders, I think it will be very important, for then we shall positively
know why the structure of every flower permits, or favours, or
necessitates an occasional cross with a distinct individual. But all
this is rather cooking my hare before I have caught it. But somehow it
is a great pleasure to me to tell you what I am about. Believe me, my
dear Gray,
Ever yours most truly, and with cordial thanks, CH. DARWIN.
CHARLES DARWIN TO G. BENTHAM. April 22, 1868.
... I am experimenting on a very large scale on the difference in power
of growth between plants raised from self-fertilised and crossed seeds;
and it is no exaggeration to say that the difference in growth and
vigour is sometimes truly wonderful. Lyell, Huxley and Hooker have seen
some of my plants, and been astonished; and I should much like to show
them to you. I always supposed until lately that no evil effects would
be visible until after several generations of self-fertilisation; but
now I see that one generation sometimes suffices; and the existence of
dimorphic plants and all the wonderful contrivances of orchids are quite
intelligible to me.
With cordial thanks for your letter, which has pleased me greatly,
Yours very sincerely, CHARLES DARWIN.
[An extract from a letter to Dr. Gray (March 11, 1873) mentions the
progress of the work:--
"I worked last summer hard at Drosera, but could not finish till I
got fresh plants, and consequently took up the effects of crossing and
sel-fertilising plants, and am got so interested that Drosera must go to
the dogs till I finish with this, and get it published; but then I will
resume my beloved Drosera, and I heartily apologise for having sent the
precious little things even for a moment to the dogs."
The following letters give the author's impression of his own book.]
CHARLES DARWIN TO J. MURRAY. Down, September 16, 1876.
My dear Sir,
I have just received proofs in sheet of five sheets, so you will have
to decide soon how many copies will have to be struck off. I do not know
what to advise. The greater part of the book is extremely dry, and the
whole on a special subject. Nevertheless, I am convinced that the book
is of value, and I am convinced that for MANY years copies will be
occasionally sold. Judging from the sale of my former books, and from
supposing that some persons will purchase it to complete the set of
my works, I would suggest 1500. But you must be guided by your larger
experience. I will only repeat that I am convinced the book is of some
permanent value...
CHARLES DARWIN TO VICTOR CARUS. Down, September 27, 1876.
My dear Sir,
I sent by this morning's post the four first perfect sheets of my new
book, the title of which you will see on the first page, and which will
be published early in November.
I am sorry to say that it is only shorter by a few pages than my
'Insectivorous Plants.' The whole is now in type, though I have
corrected finally only half the volume. You will, therefore, rapidly
receive the remainder. The book is very dull. Chapters II. to VI.,
inclusive, are simply a record of experiments. Nevertheless, I believe
(though a man can never judge his own books) that the book is valuable.
You will have to decide whether it is worth translating. I hope so. It
has cost me very great labour, and the results seem to me remarkable and
well established.
If you translate it, you could easily get aid for Chapters II. to VI.,
as there is here endless, but I have thought necessary repetition. I
shall be anxious to hear what you decide...
I most sincerely hope that your health has been fairly good this summer.
My dear Sir, yours very truly, CH. DARWIN.
CHARLES DARWIN TO ASA GRAY. Down, October 28, 1876.
My dear Gray,
I send by this post all the clean sheets as yet printed, and I hope to
send the remainder within a fortnight. Please observe that the first six
chapters are not readable, and the six last very dull. Still I believe
that the results are valuable. If you review the book, I shall be very
curious to see what you think of it, for I care more for your judgment
than for that of almost any one else. I know also that you will speak
the truth, whether you approve or disapprove. Very few will take the
trouble to read the book, and I do not expect you to read the whole, but
I hope you will read the latter chapters.
... I am so sick of correcting the press and licking my horrid bad style
into intelligible English.
[The 'Effects of Cross and Self-fertilisation' was published on November
10, 1876, and 1500 copies were sold before the end of the year. The
following letter refers to a review in 'Nature' (February 15, 1877.):]
CHARLES DARWIN TO W. THISELTON DYER. Down, February 16, 1877.
Dear Dyer,
I must tell you how greatly I am pleased and honoured by your article in
'Nature,' which I have just read. You are an adept in saying what
will please an author, not that I suppose you wrote with this express
intention. I should be very well contented to deserve a fraction of your
praise. I have also been much interested, and this is better than mere
pleasure, by your argument about the separation of the sexes. I dare
say that I am wrong, and will hereafter consider what you say more
carefully: but at present I cannot drive out of my head that the sexes
must have originated from two individuals, slightly different, which
conjugated. But I am aware that some cases of conjugation are opposed to
any such views.
With hearty thanks, Yours sincerely, CHARLES DARWIN.