More Letters of Charles Darwin Volume II

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I am particularly glad to hear that you intend to repeat my experiments on
illegitimate offspring, for no one's observations can be trusted until
repeated. You will find the work very troublesome, owing to the death of
plants and accidents of all kinds. Some dimorphic plant will probably
prove too sterile for you to raise offspring; and others too fertile for
much sterility to be expected in their offspring. Primula is bad on
account of the difficulty of deciding which seeds may be considered as
good. I have earnestly wished that some one would repeat these
experiments, but I feared that years would elapse before any one would take
the trouble. I received your paper on Bignonia in "Bot. Zeit." and it
interested me much. (678/2. See "Variation of Animals and Plants,"
Edition II., Volume II., page 117. Fritz Muller's paper,
"Befruchtungsversuche an Cipo alho (Bignonia)," "Botanische Zeitung,"
September 25th, 1868, page 625, contains an interesting foreshadowing of
the generalisation arrived at in "Cross and Self-Fertilisation." Muller
wrote: "Are the three which grow near each other seedlings from the same
mother-plant or perhaps from seeds of the same capsule? Or have they, from
growing in the same place and under the same conditions, become so like
each other that the pollen of one has hardly any more effect on the others
than their own pollen? Or, on the contrary, were the plants originally
one--i.e., are they suckers from a single stock, which have gained a slight
degree of mutual fertility in the course of an independent life? Or,
lastly, is the result 'ein neckische Zufall,'" (The above is a free
translation of Muller's words.)) I am convinced that if you can prove that
a plant growing in a distant place under different conditions is more
effective in fertilisation than one growing close by, you will make a great
step in the essence of sexual reproduction.

Prof. Asa Gray and Dr. Hooker have been staying here, and, oddly enough,
they knew nothing of your paper on Martha (678/3. F. Muller has described
("Bot. Zeitung," 1866, page 129) the explosive mechanism by which the
pollen is distributed in Martha (Posoqueria) fragrans. He also gives an
account of the remarkable arrangement for ensuring cross-fertilisation.
See "Forms of Flowers," Edition II., page 131.), though the former was
aware of the curious movements of the stamens, but so little understood the
structure of the plant that he thought it was probably a dimorphic species.
Accordingly, I showed them your drawings and gave them a little lecture,
and they were perfectly charmed with your account. Hildebrand (678/4. See
Letter 206, Volume I.) has repeated his experiments on potatoes, and so
have I, but this summer with no result.

LETTER 679. TO F. MULLER.
Down, March 14th [1869].

I received some time ago a very interesting letter from you with many facts
about Oxalis, and about the non-seeding and spreading of one species. I
may mention that our common O. acetosella varies much in length of pistils
and stamens, so that I at first thought it was certainly dimorphic, but
proved it by experiment not to be so. Boiseria (679/1. This perhaps
refers to Boissiera (Ladizabala).) has after all seeded well with me when
crossed by opposite form, but very sparingly when self-fertilised. Your
case of Faramea astonishes me. (679/2. See "Forms of Flowers," Edition
II., page 129. Faramea is placed among the dimorphic species.) Are you
sure there is no mistake? The difference in size of flower and wonderful
difference in size and structure of pollen-grains naturally make me rather
sceptical. I never fail to admire and to be surprised at the number of
points to which you attend. I go on slowly at my next book, and though I
never am idle, I make but slow progress; for I am often interrupted by
being unwell, and my subject of sexual selection has grown into a very
large one. I have also had to correct a new edition of my "Origin,"
(679/3. The 5th edition.), and this has taken me six weeks, for science
progresses at railroad speed. I cannot tell you how rejoiced I am that
your book is at last out; for whether it sells largely or not, I am certain
it will produce a great effect on all capable judges, though these are few
in number.

P.S.--I have just received your letter of January 12th. I am greatly
interested by what you say on Eschscholtzia; I wish your plants had
succeeded better. It seems pretty clear that the species is much more
self-sterile under the climate of Brazil than here, and this seems to me an
important result. (679/4. See Letter 677.) I have no spare seeds at
present, but will send for some from the nurseryman, which, though not so
good for our purpose, will be worth trying. I can send some of my own in
the autumn. You could simply cover up separately two or three single
plants, and see if they will seed without aid,--mine did abundantly. Very
many thanks for seeds of Oxalis: how I wish I had more strength and time
to carry on these experiments, but when I write in the morning, I have
hardly heart to do anything in the afternoon. Your grass is most
wonderful. You ought to send account to the "Bot. Zeitung." Could you not
ascertain whether the barbs are sensitive, and how soon they become spiral
in the bud? Your bird is, I have no doubt, the Molothrus mentioned in my
"Journal of Travels," page 52, as representing a North American species,
both with cuckoo-like habits. I know that seeds from same spike
transmitted to a certain extent their proper qualities; but as far as I
know, no one has hitherto shown how far this holds good, and the fact is
very interesting. The experiment would be well worth trying with flowers
bearing different numbers of petals. Your explanation agrees beautifully
with the hypothesis of pangenesis, and delights me. If you try other
cases, do draw up a paper on the subject of inheritance of separate flowers
for the "Bot. Zeitung" or some journal. Most men, as far as my experience
goes, are too ready to publish, but you seem to enjoy making most
interesting observations and discoveries, and are sadly too slow in
publishing.

LETTER 680. TO F. MULLER.
Barmouth, July 18th, 1869.

I received your last letter shortly before leaving home for this place.
Owing to this cause and to having been more unwell than usual I have been
very dilatory in writing to you. When I last heard, about six or eight
weeks ago, from Mr. Murray, one hundred copies of your book had been sold,
and I daresay five hundred may now be sold. (680/1. "Facts and Arguments
for Darwin," 1869: see Volume I., Letter 227.) This will quite repay me,
if not all the money; for I am sure that your book will have got into the
hands of a good many men capable of understanding it: indeed, I know that
it has. But it is too deep for the general public. I sent you two or
three reviews--one of which, in the "Athenaeum," was unfavourable; but this
journal has abused me, and all who think with me, for many years. (680/2.
"Athenaeum," 1869, page 431.) I enclose two more notices, not that they
are worth sending: some other brief notices have appeared. The case of
the Abitulon sterile with some individuals is remarkable (680/3.
"Bestaubungsversuche an Abutilon-Arten." "Jenaische Zeitschr." VII., 1873,
page 22.): I believe that I had one plant of Reseda odorata which was
fertile with own pollen, but all that I have tried since were sterile
except with pollen from some other individual. I planted the seeds of the
Abitulon, but I fear that they were crushed in the letter. Your
Eschscholtzia plants were growing well when I left home, to which place we
shall return by the end of this month, and I will observe whether they are
self-sterile. I sent your curious account of the monstrous Begonia to the
Linnean Society, and I suppose it will be published in the "Journal."
(680/4. "On the Modification of the Stamens in a Species of Begonia."
"Journ. Linn. Soc." XI., 1871, page 472.) I sent the extract about grafted
orange trees to the "Gardeners' Chronicle," where it appeared. I have
lately drawn up some notes for a French translation of my Orchis book: I
took out your letters to make an abstract of your numerous discussions, but
I found I had not strength or time to do so, and this caused me great
regret. I have [in the French edition] alluded to your work, which will
also be published in English, as you will see in my paper, and which I will
send you. (680/5. "Notes on the Fertilisation of Orchids." "Ann. Mag.
Nat. Hist." 1869, Volume IV., page 141. The paper gives an English version
of the notes prepared for the French edition of the Orchid book.)

P.S.--By an odd chance, since I wrote the beginning of this letter, I have
received one from Dr. Hooker, who has been reading "Fur Darwin": he finds
that he has not knowledge enough for the first part; but says that Chapters
X. and XI. "strike me as remarkably good." He is also particularly struck
with one of your highly suggestive remarks in the note to page 119.
Assuredly all who read your book will greatly profit by it, and I rejoice
that it has appeared in English.

LETTER 681. TO F. MULLER.
Down, December 1st [1869].

I am much obliged for your letter of October 18th, with the curious account
of Abutilon, and for the seeds. A friend of mine, Mr. Farrer, has lately
been studying the fertilisation of Passiflora (681/1. See Letters 701 and
704.), and concluded from the curiously crooked passage into the nectary
that it could not be fertilised by humming-birds; but that Tacsonia was
thus fertilised. Therefore I sent him the passage from your letter, and I
enclose a copy of his answer. If you are inclined to gratify him by making
a few observations on this subject I shall be much obliged, and will send
them on to him. I enclose a copy of my rough notes on your Eschscholtzia,
as you might like to see them. Somebody has sent me from Germany two
papers by you, one with a most curious account of Alisma (681/2. See
Letter 672.), and the other on crustaceans. Your observations on the
branchiae and heart have interested me extremely.

Alex. Agassiz has just paid me a visit with his wife. He has been in
England two or three months, and is now going to tour over the Continent to
see all the zoologists. We liked him very much. He is a great admirer of
yours, and he tells me that your correspondence and book first made him
believe in evolution. This must have been a great blow to his father, who,
as he tells me, is very well, and so vigorous that he can work twice as
long as he (the son) can.

Dr. Meyer has sent me his translation of Wallace's "Malay Archipelago,"
which is a valuable work; and as I have no use for the translation, I will
this day forward it to you by post, but, to save postage, via England.

LETTER 682. TO F. MULLER.
Down, May 12th [1870].

I thank you for your two letters of December 15th and March 29th, both
abounding with curious facts. I have been particularly glad to hear in
your last about the Eschscholtzia (682/1. See Letter 677.); for I am now
rearing crossed and self-fertilised plants, in antagonism to each other,
from your semi-sterile plants so that I may compare this comparative growth
with that of the offspring of English fertile plants. I have forwarded
your postscript about Passiflora, with the seeds, to Mr. Farrer, who I am
sure will be greatly obliged to you; the turning up of the pendant flower
plainly indicates some adaptation. When I next go to London I will take up
the specimens of butterflies, and show them to Mr. Butler, of the British
Museum, who is a learned lepidopterist and interested on the subject. This
reminds me to ask you whether you received my letter [asking] about the
ticking butterfly, described at page 33 of my "Journal of Researches";
viz., whether the sound is in anyway sexual? Perhaps the species does not
inhabit your island. (682/2. Papilio feronia, a Brazilian species capable
of making "a clicking noise, similar to that produced by a toothed wheel
passing under a spring catch."--"Journal," 1879, page 34.)

The case described in your last letter of the trimorphic monocotyledon
Pontederia is grand. (682/3. This case interested Darwin as the only
instance of heterostylism in Monocotyledons. See "Forms of Flowers,"
Edition II., page 183. F. Muller's paper is in the "Jenaische
Zeitschrift," 1871.) I wonder whether I shall ever have time to recur to
this subject; I hope I may, for I have a good deal of unpublished material.

Thank you for telling me about the first-formed flower having additional
petals, stamens, carpels, etc., for it is a possible means of transition of
form; it seems also connected with the fact on which I have insisted of
peloric flowers being so often terminal. As pelorism is strongly inherited
(and [I] have just got a curious case of this in a leguminous plant from
India), would it not be worth while to fertilise some of your early flowers
having additional organs with pollen from a similar flower, and see whether
you could not make a race thus characterised? (682/4. See Letters 588,
589. Also "Variation under Domestication," Edition II., Volume I., pages
388-9.) Some of your Abutilons have germinated, but I have been very
unfortunate with most of your seed.

You will remember having given me in a former letter an account of a very
curious popular belief in regard to the subsequent progeny of asses, which
have borne mules; and now I have another case almost exactly like that of
Lord Morton's mare, in which it is said the shape of the hoofs in the
subsequent progeny are affected. (Pangenesis will turn out true some day!)
(682/5. See "Animals and Plants," Edition II., Volume I., page 435. For
recent work on telegony see Ewart's "Experimental Investigations on
Telegony," "Phil. Trans. R. Soc." 1899. A good account of the subject is
given in the "Quarterly Review," 1899, page 404. See also Letter 275,
Volume I.)

A few months ago I received an interesting letter and paper from your
brother, who has taken up a new and good line of investigation, viz., the
adaptation in insects for the fertilisation of flowers.

The only scientific man I have seen for several months is Kolliker, who
came here with Gunther, and whom I liked extremely.

I am working away very hard at my book on man and on sexual selection, but
I do not suppose I shall go to press till late in the autumn.

LETTER 683. TO F. MULLER.
Down, January 1st, 1874.

No doubt I owe to your kindness two pamphlets received a few days ago,
which have interested me in an extraordinary degree. (683/1. This refers
to F. Muller's "Bestaubungsversuche an Abutilon-Arten" in the "Jenaische
Zeitschr." Volume VII., which are thus referred to by Darwin ("Cross and
Self Fert." pages 305-6): "Fritz Muller has shown by his valuable
experiments on hybrid Abutilons, that the union of brothers and sisters,
parents and children, and of other near relations is highly injurious to
the fertility of the offspring." The Termite paper is in the same volume
(viz., VII.) of the "Jenaische Zeitschr.") It is quite new to me what you
show about the effects of relationship in hybrids--that is to say, as far
as direct proof is concerned. I felt hardly any doubt on the subject, from
the fact of hybrids becoming more fertile when grown in number in nursery
gardens, exactly the reverse of what occurred with Gartner. (683/2. When
many hybrids are grown together the pollination by near relatives is
minimised.) The paper on Termites is even still more interesting, and the
analogy with cleistogene flowers is wonderful. (683/3. On the back of his
copy of Muller's paper Darwin wrote: "There exist imperfectly developed
male and female Termites, with wings much shorter than those of queen and
king, which serve to continue the species if a fully developed king and
queen do not after swarming (which no doubt is for an occasional cross)
enter [the] nest. Curiously like cleistogamic flowers.") The manner in
which you refer to to my chapter on crossing is one of the most elegant
compliments which I have ever received.

I have directed to be sent to you Belt's "Nicaragua," which seems to me the
best Natural History book of travels ever published. Pray look to what he
says about the leaf-carrying ant storing the leaves up in a minced state to
generate mycelium, on which he supposes that the larvae feed. Now, could
you open the stomachs of these ants and examine the contents, so as to
prove or disprove this remarkable hypothesis? (683/4. The hypothesis has
been completely confirmed by the researches of Moller, a nephew of F.
Muller's: see his "Brasilische Pilzblumen" ("Botan. Mittheilgn. aus den
Tropen," hrsg. von A.F.W. Schimper, Heft 7).)

LETTER 684. TO F. MULLER.
Down, May 9th, 1877.

I have been particularly glad to receive your letter of March 25th on
Pontederia, for I am now printing a small book on heterostyled plants, and
on some allied subjects. I feel sure you will not object to my giving a
short account of the flowers of the new species which you have sent me. I
am the more anxious to do so as a writer in the United States has described
a species, and seems to doubt whether it is heterostyled, for he thinks the
difference in the length of the pistil depends merely on its growth! In my
new book I shall use all the information and specimens which you have sent
me with respect to the heterostyled plants, and your published notices.

One chapter will be devoted to cleistogamic species, and I will just notice
your new grass case. My son Francis desires me to thank you much for your
kindness with respect to the plants which bury their seeds.

I never fail to feel astonished, when I receive one of your letters, at the
number of new facts you are continually observing. With respect to the
great supposed subterranean animal, may not the belief have arisen from the
natives having seen large skeletons embedded in cliffs? I remember finding
on the banks of the Parana a skeleton of a Mastodon, and the Gauchos
concluded that it was a borrowing animal like the Bizcacha. (684/1. On
the supposed existence in Patagonia of a gigantic land-sloth, see "Natural
Science," XIII., 1898, page 288, where Ameghino's discovery of the skin of
Neomylodon listai was practically first made known, since his privately
published pamphlet was not generally seen. The animal was afterwards
identified with a Glossotherium, closely allied to Owen's G. Darwini, which
has been named Glossotherium listai or Grypotherium domesticum. For a good
account of the discoveries see Smith Woodward in "Natural Science," XV.,
1899, page 351, where the literature is given.)

LETTER 685. TO F. MULLER.
Down, May 14th [1877].

I wrote to you a few days ago to thank you about Pontederia, and now I am
going to ask you to add one more to the many kindnesses which you have done
for me. I have made many observations on the waxy secretion on leaves
which throw off water (e.g., cabbage, Tropoeolum), and I am now going to
continue my observations. Does any sensitive species of Mimosa grow in
your neighbourhood? If so, will you observe whether the leaflets keep shut
during long-continued warm rain. I find that the leaflets open if they are
continuously syringed with water at a temperature of about 19 deg C., but
if the water is at a temperature of 33-35 deg C., they keep shut for more
than two hours, and probably longer. If the plant is continuously shaken
so as to imitate wind the leaflets soon open. How is this with the native
plants during a windy day? I find that some other plants--for instance,
Desmodium and Cassia--when syringed with water, place their leaves so that
the drops fall quickly off; the position assumed differing somewhat from
that in the so-called sleep. Would you be so kind as to observe whether
any [other] plants place their leaves during rain so as to shoot off the
water; and if there are any such I should be very glad of a leaf or two to
ascertain whether they are coated with a waxy secretion. (685/1. See
Letters 737-41.)

There is another and very different subject, about which I intend to write,
and should be very glad of a little information. Are earthworms
(Lumbricus) common in S. Brazil (685/2. F. Muller's reply is given in
"Vegetable Mould," page 122.), and do they throw up on the surface of the
ground numerous castings or vermicular masses such as we so commonly see in
Europe? Are such castings found in the forests beneath the dead withered
leaves? I am sure I can trust to your kindness to forgive me for asking
you so many questions.

LETTER 686. TO F. MULLER.
Down, July 24th, 1878.

Many thanks for the five kinds of seeds; all have germinated, and the
Cassia seedlings have interested me much, and I daresay that I shall find
something curious in the other plants. Nor have I alone profited, for Sir
J. Hooker, who was here on Sunday, was very glad of some of the seeds for
Kew. I am particularly obliged for the information about the earthworms.
I suppose the soil in your forests is very loose, for in ground which has
lately been dug in England the worms do not come to the surface, but
deposit their castings in the midst of the loose soil.

I have some grand plants (and I formerly sent seeds to Kew) of the
cleistogamic grass, but they show no signs of producing flowers of any kind
as yet. Your case of the panicle with open flowers being sterile is
parallel to that of Leersia oryzoides. I have always fancied that
cross-fertilisation would perhaps make such panicles fertile. (686/1. The
meaning of this sentence is somewhat obscure. Darwin apparently implies
that the perfect flowers, borne on the panicles which occasionally emerge
from the sheath, might be fertile if pollinated from another individual.
See "Forms of Flowers," page 334.)

I am working away as hard as I can at all the multifarious kinds of
movements of plants, and am trying to reduce them to some simple rules, but
whether I shall succeed I do not know.

I have sent the curious lepidopteron case to Mr. Meldola.

LETTER 687. F. MULLER TO CHARLES DARWIN.

(687/1. In November, 1880, on receipt of an account of a flood in Brazil
from which Fritz Muller had barely escaped with his life ("Life and
Letters," III., 242); Darwin immediately wrote to Hermann Muller begging to
be allowed to help in making good any loss in books or scientific
instruments that his brother had sustained. It is this offer of help that
is referred to in the first paragraph of the following letter: Darwin
repeats the offer in Letter 690.)

Blumenau, Sa Catharina, Brazil, January 9th, 1881.

I do not know how to express [to] you my deep heartfelt gratitude for the
generous offer which you made to my brother on hearing of the late dreadful
flood of the Itajahy. From you, dear sir, I should have accepted
assistance without hesitation if I had been in need of it; but fortunately,
though we had to leave our house for more than a week, and on returning
found it badly damaged, my losses have not been very great.

I must thank you also for your wonderful book on the movements of plants,
which arrived here on New Year's Day. I think nobody else will have been
delighted more than I was with the results which you have arrived at by so
many admirably conducted experiments and observations; since I observed the
spontaneous revolving movement of Alisma I had seen similar movements in so
many and so different plants that I felt much inclined to consider
spontaneous revolving movement or circumnutation as common to all plants
and the movements of climbing plants as a special modification of that
general phenomenon. And this you have now convincingly, nay,
superabundantly, proved to be the case.

I was much struck with the fact that with you Maranta did not sleep for two
nights after having its leaves violently shaken by wind, for here we have
very cold nights only after storms from the west or south-west, and it
would be very strange if the leaves of our numerous species of Marantaceae
should be prevented by these storms to assume their usual nocturnal
position, just when nocturnal radiation was most to be feared. It is
rather strange, also, that Phaseolus vulgaris should not sleep during the
early part of the summer, when the leaves are most likely to be injured
during cold nights. On the contrary, it would not do any harm to many sub-
tropical plants, that their leaves must be well illuminated during the day
in order that they may assume at night a vertical position; for, in our
climate at least, cold nights are always preceded by sunny days.

Of nearly allied plants sleeping very differently I can give you some more
instances. In the genus Olyra (at least, in the one species observed by
me) the leaves bend down vertically at night; now, in Endlicher's "Genera
plantarum" this genus immediately precedes Strephium, the leaves of which
you saw rising vertically.