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More Letters of Charles Darwin Volume II by Charles Darwin

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little fact, which none of my reviewers have noticed.

Down, May 23rd [1863].

You can confer a real service on a good man, John Scott, the writer of the
enclosed letter, by reading it and giving me your opinion. I assure [you]
John Scott is a truly remarkable man. The part struck out is merely that
he is not comfortable under Mr. McNab, and this part must be considered as
private. Now the question is, what think you of the offer? Is expense of
living high at Darjeeling? May I say it is healthy? Will he find the
opportunity for experimental observations, which are a passion with him?
It seems to me rather low pay. Will you advise me for him? I shall say
that as far as experiments in hand at the Botanical Garden in Edinburgh are
concerned, it would be a pity to hesitate to accept the offer.

J. Scott is head of the propagating department. I know you will not grudge
aiding by your advice a good man. I shall tell him that I have not the
slightest power to aid him in any way for the appointment. I should think
voyage out and home ought to be paid for?

Down, May 25th, 1863.

Now for a few words on science. I do not think I could be mistaken about
the stigma of Bolbophyllum (644/1. Bolbophyllum is remarkable for the
closure of the stigmatic cavity which comes on after the flower has been
open a little while, instead of after fertilisation, as in other genera.
Darwin connects the fact with the "exposed condition of the whole flower."
--"Fertilisation of Orchids," Edition II., page 137.); I had the plant
alive from Kew, and watched many flowers. That is a most remarkable
observation on foreign pollen emitting tubes, but not causing orifice to
close (644/2. See Scott, "Bot. Soc. Edin." 1863, page 546, note. He
applied pollinia from Cypripedium and Asclepias to flowers of Tricopilia
tortilis; and though the pollen germinated, the stigmatic chamber remained
open, yet it invariably closes eighteen hours after the application of its
own pollen.); it would have been interesting to have observed how close an
alliance of form would have acted on the orifice of the stigma. It will
probably be so many years, if ever, [before] I work up my observations on
Drosera, that I will not trouble you to send your paper, for I could not
now find time to read it. If you have spare copy of your Orchid paper,
please send it, but do not get a copy of the journal, for I can get one,
and you must often want to buy books. Let me know when it is published. I
have been glad to hear about Mercurialis, but I will not accept your offer
of seed on account of time, time, time, and weak health. For the same
reason I must give up Primula mollis. What a wonderful, indefatigable
worker you are! You seem to have made a famous lot of interesting
experiments. D. Beaton once wrote that no man could cross any species of
Primula. You have apparently proved the contrary with a vengeance. Your
numerous experiments seem very well selected, and you will exhaust the
subject. Now when you have completed your work you should draw up a paper,
well worth publishing, and give a list of all the dimorphic and non-
dimorphic forms. I can give you, on the authority of Prof. Treviranus in
"Bot. Zeitung," case of P. longiflora non-dimorphic. I am surprised at
your cowslips in this state. Is it a common yellow cowslip? I have seen
oxlips (which from some experiments I now look at as certainly natural
hybrids) in same state. If you think the Botanical Society of Edinburgh
would not do justice and publish your paper, send it to me to be
communicated to the Linnean Society. I will delay my paper on successive
dimorphic generations in Primula (644/3. Published in the "Journ. Linn.
Soc." X., 1869 [1868].) till yours appears, so as in no way to interfere
with your paper. Possibly my results may be hardly worth publishing, but I
think they will; the seedlings from two successive homomorphic generations
seem excessively sterile. I will keep this letter till I hear from Dr.
Hooker. I shall be very glad if you try Passiflora. Your experiments on
Primula seem so well chosen that whatever the result is they will be of
value. But always remember that not one naturalist out of a dozen cares
for really philosophical experiments.

Down, May 31st [1863].

I am unwell, and must write briefly. I am very much obliged for the
"Courant." (645/1. The Edinburgh "Evening Courant" used to publish
notices of the papers read at the Botanical Society of Edinburgh. The
paper referred to here was Scott's on Oncidium.) The facts will be of
highest use to me. I feel convinced that your paper will have permanent
value. Your case seems excellently and carefully worked out. I agree that
the alteration of title was unfortunate, but, after all, title does not
signify very much. So few have attended to such points that I do not
expect any criticism; but if so, I should think you had much better reply,
but I could if you wished it much. I quite understand about the cases
being individual sterility; so Gartner states it was with him. Would it be
worth while to send a corrected copy of the "Courant" to the "Gardeners'
Chronicle?" (645/2. An account of Scott's work appeared in the
"Gardeners' Chronicle," June 13th, 1863, which is, at least partly, a
reprint of the "Courant," since it contains the awkward sentence criticised
by Darwin and referred to below. The title is "On the Fertilisation of
Orchids," which was no doubt considered unfortunate as not suggesting the
subject of the paper, and as being the same as that of Darwin's book.) I
did not know that you had tried Lobelia fulgens: can you give me any
particulars on the number of plants and kinds used, etc., that I may quote,
as in a few days I shall be writing on this whole subject? No one will
ever convince me that it is not a very important subject to philosophical
naturalists. The Hibiscus seems a very curious case, and I agree with your
remarks. You say that you are glad of criticisms (by the way avoid "former
and latter," the reader is always forced to go back to look). I think you
would have made the case more striking if you had first showed that the
pollen of Oncidium sphacelatum was good; secondly, that the ovule was
capable of fertilisation; and lastly, shown that the plant was impotent
with its own pollen. "Impotence of organs capable of elimination"--capable
here strictly refers to organs; you mean to impotence. To eliminate
impotence is a curious expression; it is removing a non-existent quality.
But style is a trifle compared with facts, and you are capable of writing
well. I find it a good rule to imagine that I want to explain the case in
as few and simple words as possible to one who knows nothing of the
subject. (645/3. See Letter 151, Volume I.) I am tired. In my opinion
you are an excellent observer.

Down, June 6th, 1863.

I fear that you think that I have done more than I have with respect to Dr.
Hooker. I did not feel that I had any right to ask him to remember you for
a colonial appointment: all that I have done is to speak most highly of
your scientific merits. Of course this may hereafter fructify. I really
think you cannot go on better, for educational purposes, than you are now
doing,--observing, thinking, and some reading beat, in my opinion, all
systematic education. Do not despair about your style; your letters are
excellently written, your scientific style is a little too ambitious. I
never study style; all that I do is to try to get the subject as clear as I
can in my own head, and express it in the commonest language which occurs
to me. But I generally have to think a good deal before the simplest
arrangement and words occur to me. Even with most of our best English
writers, writing is slow work; it is a great evil, but there is no help for
it. I am sure you have no cause to despair. I hope and suppose your
sending a paper to the Linnean Society will not offend your Edinburgh
friends; you might truly say that you sent the paper to me, and that (if it
turns out so) I thought it worth communicating to the Linnean Society. I
shall feel great interest in studying all your facts on Primula, when they
are worked out and the seed counted. Size of capsules is often very
deceptive. I am astonished how you can find time to make so many
experiments. If you like to send me your paper tolerably well written, I
would look it over and suggest any criticisms; but then this would cause
you extra copying. Remember, however, that Lord Brougham habitually wrote
everything important three times over. The cases of the Primulae which
lose by variation their dimorphic characters seem to me very interesting.
I find that the mid-styled (by variation) P. sinensis is more fertile with
own pollen, even, than a heteromorphic union! If you have time it will be
very good to experiment on Linum Lewisii. I wrote formerly to Asa Gray
begging for seed. If you have time, I think experiments on any peloric
flowers would be useful. I shall be sorry (and I am certain it is a
mistake on the part of the Society) if your orchid paper is not printed in
extenso. I am now at work compiling all such cases, and shall give a very
full abstract of all your observations. I hope to add in autumn some from
you on Passiflora. I would suggest to you the advantage, at present, of
being very sparing in introducing theory in your papers (I formerly erred
much in Geology in that way): LET THEORY GUIDE YOUR OBSERVATIONS, but till
your reputation is well established be sparing in publishing theory. It
makes persons doubt your observations. How rarely R. Brown ever indulged
in theory: too seldom perhaps! Do not work too hard, and do not be
discouraged because your work is not appreciated by the majority.

July 2nd [1863?]

Many thanks for capsules. I would give table of the Auricula (647/1. In
Scott's paper ("Linn. Soc. Journ." VIII.) many experiments on the Auricula
are recorded.), especially owing to enclosed extract, which you can quote.
Your facts about varying fertility of the primulas will be appreciated by
but very few botanists; but I feel sure that the day will come when they
will be valued. By no means modify even in the slightest degree any
result. Accuracy is the soul of Natural History. It is hard to become
accurate; he who modifies a hair's breadth will never be accurate. It is a
golden rule, which I try to follow, to put every fact which is opposed to
one's preconceived opinion in the strongest light. Absolute accuracy is
the hardest merit to attain, and the highest merit. Any deviation is ruin.
Sincere thanks for all your laborious trials on Passiflora. I am very
busy, and have got two of my sons ill--I very much fear with scarlet fever;
if so, no more work for me for some days or weeks. I feel greatly
interested about your Primula cases. I think it much better to count seed
than to weigh. I wish I had never weighed; counting is more accurate,
though so troublesome.

Down, 25th [1863?]

From what you say I looked again at "Bot. Zeitung." (648/1. "Ueber
Dichogamie," "Bot. Zeit." January 1863.) Treviranus speaks of P.
longiflora as short-styled, but this is evidently a slip of the pen, for
further on, I see, he says the stigma always projects beyond anthers. Your
experiments on coloured primroses will be most valuable if proved true.
(648/2. The reference seems to be to Scott's observation that the variety
rubra of the primrose was sterile when crossed with pollen from the common
primrose. Darwin's caution to Scott was in some measure justified, for in
his experiments on seedlings raised by self-fertilisation of the Edinburgh
plants, he failed to confirm Scott's result. See "Forms of Flowers,"
Edition II., page 225. Scott's facts are in the "Journal Linn. Soc."
VIII., page 97 (read February 4th, 1864).) I will advise to best of my
power when I see MS. If evidence is not good I would recommend you, for
your reputation's sake, to try them again. It is not likely that you will
be anticipated, and it is a great thing to fully establish what in future
time will be considered an important discovery (or rediscovery, for no one
has noticed Gartner's facts). I will procure coloured primroses for next
spring, but you may rely I will not publish before you. Do not work too
hard to injure your health. I made some crosses between primrose and
cowslip, and I send the results, which you may use if you like. But
remember that I am not quite certain that I well castrated the short-styled
primrose; I believe any castration would be superfluous, as I find all
[these] plants sterile when insects are excluded. Be sure and save seed of
the crossed differently coloured primroses or cowslips which produced least
seed, to test the fertility of the quasi-hybrid seedlings. Gartner found
the common primrose and cowslip very difficult to cross, but he knew
nothing on dimorphism. I am sorry about delay [of] your orchid paper; I
should be glad of abstract of your new observations of self-sterility in
orchids, as I should probably use the new facts. There will be an
important paper in September in "Annals and Magazine of Natural History,"
on ovules of orchids being formed after application of pollen, by Dr. F.
Hildebrand of Bonn. (648/3. "Ann. Mag. Nat. Hist." XII., 1863, page 169.
The paper was afterwards published in the "Bot. Zeitung," 1863.)

Down, November 7th [1863].

Every day that I could do anything, I have read a few pages of your paper,
and have now finished it, and return it registered. (649/1. This refers
to the MS. of Scott's paper on the Primulaceae, "Linn. Soc. Journ." VIII.
[February 4th, 1864] 1865.) It has interested me deeply, and is, I am
sure, an excellent memoir. It is well arranged, and in most parts well
written. In the proof sheets you can correct a little with advantage. I
have suggested a few alterations in pencil for your consideration, and have
put in here and there a slip of paper. There will be no occasion to
rewrite the paper--only, if you agree with me, to alter a few pages. When
finished, return it to me, and I will with the highest satisfaction
communicate it to the Linnean Society. I should be proud to be the author
of the paper. I shall not have caused much delay, as the first meeting of
the Society was on November 5th. When your Primula paper is finished, if
you are so inclined, I should like to hear briefly about your Verbascum and
Passiflora experiments. I tried Verbascum, and have got the pods, but do
not know when I shall be able to see to the results. This subject might
make another paper for you. I may add that Acropera luteola was fertilised
by me, and had produced two fine pods. I congratulate you on your
excellent paper.

P.S.--In the summary to Primula paper can you conjecture what is the
typical or parental form, i.e. equal, long or short styled?

Down, [January 24th, 1864].

(650/1. Darwin's interest in Scott's Primula work is shown by the
following extracts from a letter to Hooker of January 24th, 1864, written,
therefore, before the paper was read, and also by the subsequent
correspondence with Hooker and Asa Gray. The first part of this letter
illustrates Darwin's condition during a period of especially bad health.)

As I do nothing all day I often get fidgety, and I now fancy that Charlie
or some of your family [are] ill. When you have time let me have a short
note to say how you all are. I have had some fearful sickness; but what a
strange mechanism one's body is; yesterday, suddenly, I had a slight attack
of rheumatism in my back, and I instantly became almost well, and so
wonderfully strong that I walked to the hot-houses, which must be more than
a hundred yards. I have sent Scott's paper to the Linnean Society; I feel
sure it is really valuable, but I fear few will care about it. Remember my
URGENT wish to be able to send the poor fellow a word of praise from any
one. I have had work to get him to allow me to send the paper to the
Linnean Society, even after it was written out.

Down, February 9th, 1864.

(651/1. Scott's paper on Primulaceae was read at the Linnean Society on
February 4th, 1864.)

The President, Mr. Bentham, I presume, was so much struck by your paper
that he sent me a message to know whether you would like to be elected an
associate. As only one is elected annually, this is a decided honour. The
enclosed list shows what respectable men are associates. I enclose the
rules of admission. I feel sure that the rule that if no communication is
received within three years the associate is considered to have voluntarily
withdrawn, is by no means rigorously adhered to. Therefore, I advise you
to accept; but of course the choice is quite free. You will see there is
no payment. You had better write to me on this subject, as Dr. Hooker or I
will propose you.

September 13th, 1864.

I have been greatly interested by Scott's paper. I probably overrate it
from caring for the subject, but it certainly seems to me one of the very
most remarkable memoirs on such subjects which I have ever read. From the
subject being complex, and the style in parts obscure, I suppose very few
will read it. I think it ought to be noticed in the "Natural History
Review," otherwise the more remarkable facts will never be known. Try and
persuade Oliver to do it; with the summary it would not be troublesome. I
would offer, but I have sworn to myself I will do nothing till my volume on
"Variation under Domestication" is complete. I know you will not have time
to read Scott, and therefore I will just point out the new and, as they
seem to me, important points.

Firstly, the red cowslip, losing its dimorphic structure and changing so
extraordinarily in its great production of seed with its own pollen,
especially being nearly sterile when fertilised by, or fertilising, the
common cowslip. The analogous facts with red and white primrose.
Secondly, the utter dissimilarity of action of the pollen of long- and
short-styled form of one species in crossing with a distinct species. And
many other points. Will you suggest to Oliver to review this paper? if he
does so, and if it would be of any service to him, I would (as I have
attended so much to these subjects) just indicate, with pages, leading and
new points. I could send him, if he wishes, a separate and spare copy
marked with pencil.

September 13th [1864].

(653/1. In September, 1864, Darwin wrote to Asa Gray describing Scott's
work on the Primulaceae as:--)

A paper which has interested me greatly by a gardener, John Scott; it seems
to me a most remarkable production, though written rather obscurely in
parts, but worth the labour of studying. I have just bethought me that for
the chance of your noticing it in the "Journal," I will point out the new
and very remarkable facts. I have paid the poor fellow's passage out to
India, where I hope he will succeed, as he is a most laborious and able
man, with the manners almost of a gentleman.

(653/2. The following is an abstract of the paper which was enclosed in
the letter to Asa Gray.)

Pages 106-8. Red cowslip by variation has become non-dimorphic, and with
this change of structure has become much more productive of seed than even
the heteromorphic union of the common cowslip. Pages 91-2, similar case
with Auricula; on the other hand a non-dimorphic variety of P. farinosa
(page 115) is less fertile. These changes, or variations, in the
generative system seem to me very remarkable. But far more remarkable is
the fact that the red cowslip (pages 106-8) is very sterile when
fertilising, or fertilised by the common cowslip. Here we have a new
"physiological species." Analogous facts given (page 98) on the crossing
of red and white primroses with common primroses. It is very curious that
the two forms of the same species (pages 93, 94, 95, and 117) hybridise
with extremely different degrees of facility with distinct species.

He shows (page 94) that sometimes a cross with a quite distinct species
yields more seed than a homomorphic union with own pollen. He shows (page
111) that of the two homomorphic unions possible with each dimorphic
species the short-styled (as I stated) is the most sterile, and that my
explanation is probably true. There is a good summary to the paper.


(654/1. The following letters to Hooker, April 1st, April 5th and May
22nd, refer to Darwin's scheme of employing Scott as an assistant at Down,
and to Scott's appointment to the Botanic Garden at Calcutta.)

Down, April 1st, 1864.

I shall not at present allude to your very interesting letter (which as yet
has been read to me only twice!), for I am full of a project which I much
want you to consider.

You will have seen Scott's note. He tells me he has no plans for the
future. Thinking over all his letters, I believe he is a truly remarkable
man. He is willing to follow suggestions, but has much originality in
varying his experiments. I believe years may pass before another man
appears fitted to investigate certain difficult and tedious points--viz.
relative fertility of varieties of plants, including peloric and other
monsters (already Scott has done excellent work on this head); and,
secondly, whether a plant's own pollen is less effective than that of
another individual. Now, if Scott is moderate in his wishes, I would pay
him for a year or two to work and publish on these or other such subjects
which might arise. But I dare not have him here, for it would quite
overwork me. There would not be plants sufficient for his work, and it
would probably be an injury to himself, as it would put him out of the way
of getting a good situation. Now, I believe you have gardeners at Kew who
work and learn there without pay. What do you think of having Scott there
for a year or two to work and experiment? I can see enormous difficulties.
In the first place you will not perhaps think the points indicated so
highly important as I do. Secondly, he would require ground in some
out-of-the-way place where the plants could be covered by a net, which
would be unsightly. On the other hand, I presume you would like a series
of memoirs published on work done at Kew, which I am fully convinced would
have permanent value. It would, of course I conceive, be absolutely
necessary that Scott should be under the regular orders of the
superintendent. The only way I can fancy that it could be done would be to
explain to the superintendent that I temporarily supported Scott solely for
the sake of science, and appeal to his kindness to assist him. If you
approved of having him (which I can see is improbable), and you simply
ordered the superintendent to assist him, I believe everything would go to
loggerheads. As for Scott himself, it would be of course an advantage to
him to study the cultivation at Kew. You would get to know him, and if he
really is a good man you could perhaps be able to recommend him to some
situation at home or abroad. Pray turn this [over] in your mind. I have
no idea whether Scott would like the place, but I can see that he has a
burning zeal for science. He told me that his parents were in better
circumstances, and that he chose a gardener's life solely as the best way
of following science. I may just add that in his last letter he gives me
the results of many experiments on different individuals of the same
species of orchid, showing the most remarkable diversity in their sexual
condition. It seems to me a grievous loss that such a man should have all
his work cut short. Please remember that I know nothing of him excepting
from his letters: these show remarkable talent, astonishing perseverance,
much modesty, and what I admire, determined difference from me on many

What will Sir William say?

Down, April 5th [1864].

I see my scheme for Scott has invincible difficulties, and I am very much
obliged to you for explaining them at such length. If ever I get decently
well, and Scott is free and willing, I will have him here for a couple of
years to work out several problems, which otherwise would never be done. I
cannot see what will become of the poor fellow. I enclose a little
pamphlet from him, which I suppose is not of much scientific value, but is
surprising as the work of a gardener. If you have time do just glance over
it. I never heard anything so extraordinary as what you say about
poisoning plants, etc.

...The post has just come in. Your interest about Scott is extraordinarily
kind, and I thank you cordially. It seems absurd to say so, but I suspect
that X is prejudiced against Scott because he partially supports my views.
(655/1. In a letter to Scott (dated June 11th) Darwin warns him to keep
his views "pretty quiet," and quotes Hooker's opinion that "if it is known
that you agree at all with my views on species it is enough to make you
unpopular in Edinburgh.")

You must not trust my former letter about Clematis. I worked on too old a
plant, and blundered. I have now gone over the work again. It is really
curious that the stiff peduncles are acted upon by a bit of thread weighing
.062 of a grain.

Clematis glandulosa was a valuable present to me. My gardener showed it to
me and said, "This is what they call a Clematis," evidently disbelieving
it. So I put a little twig to the peduncle, and the next day my gardener
said, "You see it is a Clematis, for it feels." That's the way we make out
plants at Down.

My dear old friend, God bless you!

[May 22nd, 1864].

What a good kind heart you have got. You cannot tell how your letter has
pleased me. I will write to Scott and ask him if he chooses to go out and
risk engagement. If he will not he must want all energy. He says himself
he wants stoicism, and is too sensitive. I hope he may not want courage.
I feel sure he is a remarkable man, with much good in him, but no doubt
many errors and blemishes. I can vouch for his high intellect (in my
judgment he is the best observer I ever came across); for his modesty, at
least in correspondence; and there is something high-minded in his
determination not to receive money from me. I shall ask him whether he can
get a good character for probity and sobriety, and whether he can get aid
from his relations for his voyage out. I will help, and, if necessary, pay
the whole voyage, and give him enough to support him for some weeks at
Calcutta. I will write when I hear from him. God bless you; you, who are
so overworked, are most generous to take so much trouble about a man you
have had nothing to do with.

(656/1. Scott had left the Botanic Gardens at Edinburgh in March 1864,
chagrined at what, justly or unjustly, he considered discouragement and
slight. The Indian offer was most gladly and gratefully accepted.)

Down, November 1st, 1871.

Dr. Hooker has forwarded to me your letter as the best and simplest plan of
explaining affairs. I am sincerely grieved to hear of the pecuniary
problem which you have undergone, but now fortunately passed. I assure you
that I have never entertained any feelings in regard to you which you
suppose. Please to remember that I distinctly stated that I did not
consider the sum which I advanced as a loan, but as a gift; and surely
there is nothing discreditable to you, under the circumstances, in
receiving a gift from a rich man, as I am. Therefore I earnestly beg you
to banish the whole subject from your mind, and begin laying up something
for yourself in the future. I really cannot break my word and accept
payment. Pray do not rob me of my small share in the credit of aiding to
put the right man in the right place. You have done good work, and I am
sure will do more; so let us never mention the subject again.

I am, after many interruptions, at work again on my essay on Expression,
which was written out once many months ago. I have found your remarks the
best of all which have been sent me, and so I state.

CHAPTER 2.XI.--BOTANY, 1863-1881.

2.XI.I. Miscellaneous, 1863-1866.--2.XI.II. Correspondence with Fritz
Muller, 1865-1881.--2.XI.III. Miscellaneous, 1868-1881.

2.XI.I. MISCELLANEOUS, 1863-1866.

Down [April, 1863].

(658/1. The following letter illustrates the truth of Sir W. Thiselton-
Dyer's remark that Darwin was never "afraid of his facts." (658/2.
"Charles Darwin" (Nature Series), 1882, page 43.) The entrance of pollen-
tubes into the nucellus by the chalaza, instead of through the micropyle,
was first fully demonstrated by Treub in his paper "Sur les Casuarinees et
leur place dans le Systeme naturel," published in the "Ann. Jard. Bot.
Buitenzorg," X., 1891. Two years later Miss Benson gave an account of a
similar phenomenon in certain Amentiferae ("Trans. Linn. Soc." 1888-94,
page 409). This chalazogamic method of fertilisation has since been
recognised in other flowering plants, but not, so far as we are aware, in
the genus Primula.)

It is a shame to trouble [you], but will you tell me whether the ovule of
Primula is "anatropal," nearly as figured by Gray, page 123, "Lessons in
Botany," or rather more tending to "amphitropal"? I never looked at such a
point before. Why I am curious to know is because I put pollen into the
ovarium of monstrous primroses, and now, after sixteen days, and not before
(the length of time agrees with slowness of natural impregnation), I find
abundance of pollen-tubes emitted, which cling firmly to the ovules, and, I
think I may confidently state, penetrate the ovule. But here is an odd
thing: they never once enter at (what I suppose to be) the "orifice," but
generally at the chalaza...Do you know how pollen-tubes go naturally in
Primula? Do they run down walls of ovarium, and then turn up the placenta,
and so debouch near the "orifices" of the ovules?

If you thought it worth while to examine ovules, I would see if there are
more monstrous flowers, and put pollen into the ovarium, and send you the
flowers in fourteen or fifteen days afterwards. But it is rather
troublesome. I would not do it unless you cared to examine the ovules.
Like a foolish and idle man, I have wasted a whole morning over them...

In two ovules there was an odd appearance, as if the outer coat of ovule at
the chalaza end (if I understand the ovule) had naturally opened or
withered where most of the pollen-tubes seemed to penetrate, which made me
at first think this was a widely open foramen. I wonder whether the ovules
could be thus fertilised?

Down [April, 1863].

Many thanks about the Primula. I see that I was pretty right about the
ovules. I have been thinking that the apparent opening at the chalaza end
must have been withering or perhaps gnawing by some very minute insects, as
the ovarium is open at the upper end. If I have time I will have another
look at pollen-tubes, as, from what you say, they ought to find their way
to the micropyle. But ovules to me are far more troublesome to dissect
than animal tissue; they are so soft, and muddy the water.

Down, April 6th [1863].

I have been very glad to read your paper on Peloria. (660/1. "On the
Existence of Two Forms of Peloria." "Natural History Review," April, 1863,
page 258.) For the mere chance of the following case being new I send it.
A plant which I purchased as Corydalis tuberosa has, as you know, one
nectary--short, white, and without nectar; the pistil is bowed towards the
true nectary; and the hood formed by the inner petals slips off towards the
opposite side (all adaptations to insect agency, like many other pretty
ones in this family). Now on my plants there are several flowers (the
fertility of which I will observe) with both nectaries equal and purple and
secreting nectar; the pistil is straight, and the hood slips off either
way. In short, these flowers have the exact structure of Dielytra and
Adlumia. Seeing this, I must look at the case as one of reversion; though
it is one of the spreading of irregularity to two sides.

As columbine [Aquilegia] has all petals, etc., irregular, and as monkshood
[Aconitum] has two petals irregular, may not the case given by Seringe, and
referred to [by] you (660/2. "Seringe describes and figures a flower [of
Aconitum] wherein all the sepals were helmet-shaped," and the petals
similarly affected. Maxwell Masters, op. cit., page 260.), by you be
looked at as reversion to the columbine state? Would it be too bold to
suppose that some ancient Linaria, or allied form, and some ancient Viola,
had all petals spur-shaped, and that all cases of "irregular peloria" in
these genera are reversions to such imaginary ancient form? (660/3.
"'Regular or Congenital Peloria' would include those flowers which,
contrary to their usual habit, retain throughout the whole of their growth
their primordial regularity of form and equality of proportion. 'Irregular
or Acquired Peloria,' on the other hand, would include those flowers in
which the irregularity of growth that ordinarily characterises some
portions of the corolla is manifested in all of them." Maxwell Masters,
loc. cit.)

It seems to me, in my ignorance, that it would be advantageous to consider
probably due to the same general law--viz., one as reversion to very early
state, and the other as reversion to a later state when all the petals were
irregularly formed. This seems at least to me a priori a more probable
view than to look at one form of Peloria as due to reversion and the other
as something distinct. (660/4. See Maxwell Masters, "Vegetable
Teratology," 1869, page 235; "Variation of Animals and Plants," Edition
II., Volume II., page 33.)

What do you think of this notion?


(661/1. The following was written in reply to Mr. Gosse's letter of May
30th asking for a solution of his difficulties in fertilising Stanhopea.
It is reprinted by the kind permission of Mr. Edmund Gosse from his
delightful book, the "Life of Philip Henry Gosse," London, 1890, page 299.)

Down, June 2nd, 1863.

It would give me real pleasure to resolve your doubts, but I cannot. I can
give only suspicions and my grounds for them. I should think the non-
viscidity of the stigmatic hollow was due to the plant not living under its
natural conditions. Please see what I have said on Acropera. An excellent
observer, Mr. J. Scott, of the Botanical Gardens, Edinburgh, finds all that
I say accurate, but, nothing daunted, he with the knife enlarged the
orifice and forced in pollen-masses; or he simply stuck them into the
contracted orifice without coming into contact with the stigmatic surface,
which is hardly at all viscid, when, lo and behold, pollen-tubes were
emitted and fine seed capsules obtained. This was effected with Acropera
Loddigesii; but I have no doubt that I have blundered badly about A.
luteola. I mention all this because, as Mr. Scott remarks, as the plant is
in our hot-houses, it is quite incredible it ever could be fertilised in
its native land. The whole case is an utter enigma to me. Probably you
are aware that there are cases (and it is one of the oddest facts in
Physiology) of plants which, under culture, have their sexual functions in
so strange a condition, that though their pollen and ovules are in a sound
state and can fertilise and be fertilised by distinct but allied species,
they cannot fertilise themselves. Now, Mr. Scott has found this the case
with certain orchids, which again shows sexual disturbance. He had read a
paper at the Botanical Society of Edinburgh, and I daresay an abstract
which I have seen will appear in the "Gardeners' Chronicle"; but blunders
have crept in in copying, and parts are barely intelligible. How insects
act with your Stanhopea I will not pretend to conjecture. In many cases I
believe the acutest man could not conjecture without seeing the insect at
work. I could name common English plants in this predicament. But the
musk-orchis [Herminium monorchis] is a case in point. Since publishing, my
son and myself have watched the plant and seen the pollinia removed, and
where do you think they invariably adhere in dozens of specimens?--always
to the joint of the femur with the trochanter of the first pair of legs,
and nowhere else. When one sees such adaptation as this, it would be
hopeless to conjecture on the Stanhopea till we know what insect visits it.
I have fully proved that my strong suspicion was correct that with many of
our English orchids no nectar is excreted, but that insects penetrate the
tissues for it. So I expect it must be with many foreign species. I
forgot to say that if you find that you cannot fertilise any of your
exotics, take pollen from some allied form, and it is quite probable that
will succeed. Will you have the kindness to look occasionally at your bee-
Ophrys near Torquay, and see whether pollinia are ever removed? It is my
greatest puzzle. Please read what I have said on it, and on O. arachnites.
I have since proved that the account of the latter is correct. I wish I
could have given you better information.

P.S.--If the Flowers of the Stanhopea are not too old, remove pollen-masses
from their pedicels, and stick them with a little liquid pure gum to the
stigmatic cavity. After the case of the Acropera, no one can dare
positively say that they would not act.

Down, Saturday, 5th [December 1863].

I am very glad that this will reach you at Kew. You will then get rest,
and I do hope some lull in anxiety and fear. Nothing is so dreadful in
this life as fear; it still sickens me when I cannot help remembering some
of the many illnesses our children have endured. My father, who was a
sceptical man, was convinced that he had distinctly traced several cases of
scarlet fever to handling letters from convalescents.

The vases (662/1. Probably Wedgwood ware.) did come from my sister Susan.
She is recovering, and was much pleased to hear that you liked them; I have
now sent one of your notes to her, in which you speak of them as
"enchanting," etc. I have had a bad spell--vomiting, every day for eleven
days, and some days many times after every meal. It is astonishing the
degree to which I keep up some strength. Dr. Brinton was here two days
ago, and says he sees no reason [why] I may not recover my former degree of
health. I should like to live to do a little more work, and often I feel
sure I shall, and then again I feel that my tether is run out.

Your Hastings note, my dear old fellow, was a Copley Medal to me and more
than a Copley Medal: not but what I know well that you overrate what I
have been able to do. (662/2. The proposal to give the medal to Darwin
failed in 1863, but his friends were successful in 1864: see "Life and
Letters," III., page 28.) Now that I am disabled, I feel more than ever
what a pleasure observing and making out little difficulties is. By the
way, here is a very little fact which may interest you. A partridge foot
is described in "Proc. Zoolog. Soc." with a huge ball of earth attached to
it as hard as rock. (662/3. "Proc. Zool. Soc." 1863, page 127, by Prof.
Newton, who sent the foot to Darwin: see "Origin," Edition VI., page 328.)
Bird killed in 1860. Leg has been sent me, and I find it diseased, and no
doubt the exudation caused earth to accumulate; now already thirty-two
plants have come up from this ball of earth.

By Jove! I must write no more. Good-bye, my best of friends.

There is an Italian edition of the "Origin" preparing. This makes the
fifth foreign edition--i.e. in five foreign countries. Owen will not be
right in telling Longmans that the book would be utterly forgotten in ten
years. Hurrah!

Down, February 17th [1864].

Many thanks for the Epacrids, which I have kept, as they will interest me
when able to look through the microscope.

Dr. Cruger has sent me the enclosed paper, with power to do what I think
fit with it. He would evidently prefer it to appear in the "Nat. Hist.
Review." Please read it, and let me have your decision pretty soon. Some
germanisms must be corrected; whether woodcuts are necessary I have not
been able to pay attention enough to decide. If you refuse, please send it
to the Linnean Society as communicated by me. (663/1. H. Cruger's "A Few
Notes on the Fecundation of Orchids, etc." [Read March, 1864.] "Linn. Soc.
Journ." VIII., 1864-5, page 127.) The paper has interested me extremely,
and I shall have no peace till I have a good boast. The sexes are separate
in Catasetum, which is a wonderful relief to me, as I have had two or three
letters saying that the male C. tridentatum seeds. (663/2. See footnote
Letter 608 on the sexual relation between the three forms known as
Catasetum tridentatum, Monacanthus viridis, and Myanthus barbatus. For
further details see Darwin, "Linn. Soc. Journ." VI., 1862, page 151, and
"Fertilisation of Orchids," Edition II., page 196.) It is pretty clear to
me that two or three forms are confounded under this name. Observe how
curiously nearly perfect the pollen of the female is, according to Cruger,
--certainly more perfect than the pollen from the Guyana species described
by me. I was right in the manner in which the pollen adheres to the hairy
back of the humble-bee, and hence the force of the ejection of the pollina.
(663/3. This view was given in "Fertilisation of Orchids," Edition I.,
1862, page 230.) I am still more pleased that I was right about insects
gnawing the fleshy labellum. This is important, as it explains all the
astounding projections on the labellum of Oncidium, Phalaenopsis, etc.

Excuse all my boasting. It is the best medicine for my stomach. Tell me
whether you mean to take up orchids, as Hooker said you were thinking of
doing. Do you know Coryanthes, with its wonderful basket of water? See
what Cruger says about it. It beats everything in orchids. (663/4. For
Coryanthes see "Fertilisation of Orchids," Edition II., page 173.)

Down [September 13th, 1864].

Thanks for your note of the 5th. You think much and greatly too much of me
and my doings; but this is pleasant, for you have represented for many
years the whole great public to me.

I have read with interest Bentham's address on hybridism. I am glad that
he is cautious about Naudin's view, for I cannot think that it will hold.
(664/1. C. Naudin's "Nouvelles Recherches sur l'Hydridite dans les
Vegetaux." The complete paper, with coloured plates, was presented to the
Academy in 1861, and published in full in the "Nouvelles Archives de Museum
d'Hist. Nat." Volume I., 1865, page 25. The second part only appeared in
the "Ann. Sci. Nat." XIX., 1863. Mr. Bentham's address dealing with
hybridism is in "Proc. Linn. Soc." VIII., 1864, page ix. A review of
Naudin is given in the "Natural History Review," 1864, page 50. Naudin's
paper is of much interest, as containing a mechanical theory of
reproduction of the same general character as that of pangenesis. In the
"Variation of Animals and Plants," Edition II., Volume II., page 395,
Darwin states that in his treatment of hybridism in terms of gemmules he is
practically following Naudin's treatment of the same theme in terms of
"essences." Naudin, however, does not clearly distinguish between hybrid
and pure gemmules, and makes the assumption that the hybrid or mixed
essences tend constantly to dissociate into pure parental essences, and
thus lead to reversion. It is to this view that Darwin refers when he says
that Naudin's view throws no light on the reversion to long-lost
characters. His own attempt at explaining this fact occurs in "Variation
under Domestication," II., Edition II., page 395. Mr. Bateson ("Mendel's
Principle of Heredity," Cambridge, 1902, page 38) says: "Naudin clearly
enuntiated what we shall henceforth know as the Mendelian conception of the
dissociation of characters of cross-breds in the formation of the germ-
cells, though apparently he never developed this conception." It is
remarkable that, as far as we know, Darwin never in any way came across
Mendel's work. One of Darwin's correspondents, however, the late Mr. T.
Laxton, of Stamford, was close on the trail of Mendelian principle. Mr.
Bateson writes (op. cit., page 181): "Had he [Laxton] with his other gifts
combined this penetration which detects a great principle hidden in the
thin mist of 'exceptions,' we should have been able to claim for him that
honour which must ever be Mendel's in the history of discovery.") The
tendency of hybrids to revert to either parent is part of a wider law
(which I am fully convinced that I can show experimentally), namely, that
crossing races as well as species tends to bring back characters which
existed in progenitors hundreds and thousands of generations ago. Why this
should be so, God knows. But Naudin's view throws no light, that I can
see, on this reversion of long-lost characters. I wish the Ray Society
would translate Gartner's "Bastarderzeugung"; it contains more valuable
matter than all other writers put together, and would do great service if
better known. (664/2. "Versuche uber die Bastarderzeugung im
Pflanzenreich": Stuttgart, 1849.)


(665/1. Mr. Huxley had doubted the accuracy of observations on Catasetum
published in the "Fertilisation of Orchids." In what formed the postscript
to the following letter, Darwin wrote: "I have had more Catasetums,--all
right, you audacious 'caviller.'")

Down, October 31st [1862].

In a little book, just published, called the "Three Barriers" (a
theological hash of old abuse of me), Owen gives to the author a new resume
of his brain doctrine; and I thought you would like to hear of this. He
ends with a delightful sentence. "No science affords more scope or easier
ground for the caviller and controversialist; and these do good by
preventing scholars from giving more force to generalisations than the
master propounding them does, or meant his readers or hearers to give."

You will blush with pleasure to hear that you are of some use to the

[February, 1864?]

I shall write again. I write now merely to ask, if you have Naravelia
(666/1. Ranunculaceae.) (the Clematis-like plant told me by Oliver), to
try and propagate me a plant at once. Have you Clematis cirrhosa? It will
amuse me to tell you why Clematis interests me, and why I should so very
much like to have Naravelia. The leaves of Clematis have no spontaneous
movement, nor have the internodes; but when by growth the peduncles of
leaves are brought into contact with any object, they bend and catch hold.
The slightest stimulus suffices, even a bit of cotton thread a few inches
long; but the stimulus must be applied during six or twelve hours, and when
the peduncles once bend, though the touching object be removed, they never
get straight again. Now mark the difference in another leaf-climber--viz.,
Tropaeolum: here the young internodes revolve day and night, and the
peduncles of the leaves are thus brought into contact with an object, and
the slightest momentary touch causes them to bend in any direction and
catch the object, but as the axis revolves they must be often dragged away
without catching, and then the peduncles straighten themselves again, and
are again ready to catch. So that the nervous system of Clematis feels
only a prolonged touch--that of Tropaeolum a momentary touch: the
peduncles of the latter recover their original position, but Clematis, as
it comes into contact by growth with fixed objects, has no occasion to
recover its position, and cannot do so. You did send me Flagellaria, but
most unfortunately young plants do not have tendrils, and I fear my plant
will not get them for another year, and this I much regret, as these leaf-
tendrils seem very curious, and in Gloriosa I could not make out the
action, but I have now a young plant of Gloriosa growing up (as yet with
simple leaves) which I hope to make out. Thank Oliver for decisive answer
about tendrils of vines. It is very strange that tendrils formed of
modified leaves and branches should agree in all their four highly
remarkable properties. I can show a beautiful gradation by which LEAVES
produce tendrils, but how the axis passes into a tendril utterly puzzles
me. I would give a guinea if vine-tednrils could be found to be leaves.

(666/2. It is an interesting fact that Darwin's work on climbing plants
was well advanced before he discovered the existence of the works of Palm,
Mohl, and Dutrochet on this subject. On March 22nd, 1864, he wrote to
Hooker:--"You quite overrate my tendril work, and there is no occasion to
plague myself about priority." In June he speaks of having read "two
German books, and all, I believe, that has been written on climbers, and it
has stirred me up to find that I have a good deal of new matter.")

Down, June 2nd [1864].

You once offered me a Combretum. (667/1. The two forms of shoot in C.
argenteum are described in "Climbing Plants," page 41.) I having C.
purpureum, out of modesty like an ass refused. Can you now send me a
plant? I have a sudden access of furor about climbers. Do you grow
Adlumia cirrhosa? Your seed did not germinate with me. Could you have a
seedling dug up and potted? I want it fearfully, for it is a leaf-climber,
and therefore sacred.

I have some hopes of getting Adlumia, for I used to grow the plant, and
seedlings have often come up, and we are now potting all minute reddish-
coloured weeds. (667/2. We believe that the Adlumia which came up year by
year in flower boxes in the Down verandah grew from seed supplied by Asa
Gray.) I have just got a plant with sensitive axis, quite a new case; and
tell Oliver I now do not care at all how many tendrils he makes axial,
which at one time was a cruel torture to me.

Down, November 3rd [1864].

Many thanks for your splendid long letter. But first for business. Please
look carefully at the enclosed specimen of Dicentra thalictriformis, and
throw away. (668/1. Dicentra thalictrifolia, a Himalayan species of
Fumariaceae, with leaf-tendrils.) When the plant was young I concluded
certainly that the tendrils were axial, or modified branches, which Mohl
says is the case with some Fumariaceae. (668/2. "Ueber den Bau und das
Winden der Ranken und Schlingpflanzen. Eine gekronte Preisschrift," 4to,
Tubingen, 1827. At page 43 Mohl describes the tips of the branches of
Fumaria [Corydalis] clavicualta as being developed into tendrils, as well
as the leaves. For this reason Darwin placed the plant among the tendril-
bearers rather than among the true leaf-climbers: see "Climbing Plants,"
Edition II., 1875, page 121.) You looked at them here and agreed. But now
the plant is old, what I thought was a branch with two leaves and ending in
a tendril looks like a gigantic leaf with two compound leaflets, and the
terminal part converted into a tendril. For I see buds in the fork between
supposed branch and main stem. Pray look carefully--you know I am
profoundly ignorant--and save me from a horrid mistake.


(669/1. The following is interesting, as containing a foreshadowing of the
chemotaxis of antherozoids which was shown to exist by Pfeffer in 1881:
see "Untersuchungen aus dem botanischen Institut zu Tubingen," Volume I.,
page 363. There are several papers by H.J. Carter on the reproduction of
the lower organisms in the "Annals and Magazine of Natural History" between
1855 and 1865.)

Down, Sunday, 22nd, and Saturday, 28th [October, 1865].

I have been wading through the "Annals and Mag. of N. History." for last
ten years, and have been interested by several papers, chiefly, however,
translations; but none have interested me more than Carter's on lower
vegetables, infusoria, and protozoa. Is he as good a workman as he
appears? for if so he would deserve a Royal medal. I know it is not new;
but how wonderful his account of the spermatozoa of some dioecious alga or
conferva, swimming and finding the minute micropyle in a distinct plant,
and forcing its way in! Why, these zoospores must possess some sort of
organ of sense to guide their locomotive powers to the small micropyle; and
does not this necessarily imply something like a nervous system, in the
same way as complemental male cirripedes have organs of sense and
locomotion, and nothing else but a sack of spermatozoa?

May 16th, 1866.

Since writing to you before, I have read your admirable memoir on Salvia
(670/1. "Pringsheim's Jahrbucher," Volume IV., 1866.), and it has
interested me almost as much as when I first investigated the structure of
orchids. Your paper illustrates several points in my "Origin of Species,"
especially the transition of organs. Knowing only two or three species in
the genus, I had often marvelled how one cell of the anther could have been
transformed into the moveable plate or spoon; and how well you show the
gradations. But I am surprised that you did not more strongly insist on
this point.

I shall be still more surprised if you do not ultimately come to the same
belief with me, as shown by so many beautiful contrivances,--that all
plants require, from some unknown cause, to be occasionally fertilised by
pollen from a distinct individual.



(671/1. The letters from Darwin to Muller are given as a separate group,
instead of in chronological sequence with the other botanical letters, as
better illustrating the uninterrupted friendship and scientific comradeship
of the two naturalists.)

Down, October 17th [1865].

I received about a fortnight ago your second letter on climbing plants,
dated August 31st. It has greatly interested me, and it corrects and fills
up a great hiatus in my paper. As I thought you could not object, I am
having your letter copied, and will send the paper to the Linnean Society.
(671/2. "Notes on some of the Climbing Plants near Desterro" [1865],
"Linn. Soc. Journ." IX., 1867.) I have slightly modified the arrangement
of some parts and altered only a few words, as you write as good English as
an Englishman. I do not quite understand your account of the arrangement
of the leaves of Strychnos, and I think you use the word "bracteae"
differently to what English authors do; therefore I will get Dr. Hooker to
look over your paper.

I cannot, of course, say whether the Linnean Society will publish your
paper; but I am sure it ought to do so. As the Society is rather poor, I
fear that it will give only a few woodcuts from your truly admirable


(672/1. In Darwin's book on Climbing Plants, 1875 (672/2. First given as
a paper before the Linnean Society, and published in the "Linn. Soc.
Journ." Volume IX.,), he wrote (page 205): "The conclusion is forced on
our minds that the capacity of revolving, on which most climbing plants
depend, is inherent, though undeveloped, in almost every plant in the
vegetable Kingdom"--a conclusion which was verified in the "Power of
Movement in Plants." The present letter is interesting in referring to
Fritz Muller's observations on the "revolving nutation," or circumnutation
of Alisma macrophylla and Linum usitatissimum, the latter fact having been
discovered by F. Muller's daughter Rosa. This was probably the earliest
observation on the circumnutation of a non-climbing plant, and Muller, in a
paper dated 1868, and published in Volume V. of the "Jenaische
Zeitschrift," page 133, calls attention to its importance in relation to
the evolution of the habit of climbing. The present letter was probably
written in 1865, since it refers to Muller's paper read before the Linnean
Soc. on December 7th, 1865. If so, the facts on circumnutation must have
been communicated to Darwin some years before their publication in the
"Jenaische Zeitschrift.")

Down, December 9th [1865].

I have received your interesting letter of October 10th, with its new facts
on branch-tendrils. If the Linnean Society publishes your paper (672/3.
Ibid., 1867, page 344.), as I am sure it ought to do, I will append a note
with some of these new facts.

I forwarded immediately your MS. to Professor Max Schultze, but I did not
read it, for German handwriting utterly puzzles me, and I am so weak, I am
capable of no exertion. I took the liberty, however, of asking him to send
me a copy, if separate ones are printed, and I reminded him about the
Sponge paper.

You will have received before this my book on orchids, and I wish I had
known that you would have preferred the English edition. Should the German
edition fail to reach you, I will send an English one. That is a curious
observation of your daughter about the movement of the apex of the stem of
Linum, and would, I think, be worth following out. (672/4. F. Muller,
"Jenaische Zeitschrift," Bd. V., page 137. Here, also, are described the
movements of Alisma.) I suspect many plants move a little, following the
sun; but all do not, for I have watched some pretty carefully.

I can give you no zoological news, for I live the life of the most secluded

I occasionally hear from Ernest Hackel, who seems as determined as you are
to work out the subject of the change of species. You will have seen his
curious paper on certain medusae reproducing themselves by seminal
generation at two periods of growth.

(672/5. On April 3rd, 1868, Darwin wrote to F. Muller: "Your diagram of
the movements of the flower-peduncle of the Alisma is extremely curious. I
suppose the movement is of no service to the plant, but shows how easily
the species might be converted into a climber. Does it bend through
irritability when rubbed?"

Down, September 25th [1866].

I have just received your letter of August 2nd, and am, as usual,
astonished at the number of interesting points which you observe. It is
quite curious how, by coincidence, you have been observing the same
subjects that have lately interested me.

Your case of the Notylia is quite new to me (673/1. See F. Muller, "Bot.
Zeitung," 1868, page 630; "Fertilisation of Orchids," Edition II., page
171.); but it seems analogous with that of Acropera, about the sexes of
which I blundered greatly in my book. I have got an Acropera now in
flower, and have no doubt that some insect, with a tuft of hairs on its
tail, removes by the tuft, the pollinia, and inserts the little viscid cap
and the long pedicel into the narrow stigmatic cavity, and leaves it there
with the pollen-masses in close contact with, but not inserted into, the
stigmatic cavity. I find I can thus fertilise the flowers, and so I can
with Stanhopea, and I suspect that this is the case with your Notylia. But
I have lately had an orchis in flower--viz. Acineta, which I could not
anyhow fertilise. Dr. Hildebrand lately wrote a paper (673/2. "Bot.
Zeitung," 1863, 1865.) showing that with some orchids the ovules are not
mature and are not fertilised until months after the pollen-tubes have
penetrated the column, and you have independently observed the same fact,
which I never suspected in the case of Acropera. The column of such
orchids must act almost like the spermatheca of insects. Your orchis with
two leaf-like stigmas is new to me; but I feel guilty at your wasting your
valuable time in making such beautiful drawings for my amusement.

Your observations on those plants being sterile which grow separately, or
flower earlier than others, are very interesting to me: they would be
worth experimenting on with other individuals. I shall give in my next
book several cases of individual plants being sterile with their own
pollen. I have actually got on my list Eschscholtzia (673/3. See "Animals
and Plants," II., Edition II., page 118.) for fertilising with its own
pollen, though I did not suspect it would prove sterile, and I will try
next summer. My object is to compare the rate of growth of plants raised
from seed fertilised by pollen from the same flower and by pollen from a
distinct plant, and I think from what I have seen I shall arrive at
interesting results. Dr. Hildebrand has lately described a curious case of
Corydalis cava which is quite sterile with its own pollen, but fertile with
pollen of any other individual plant of the species. (673/4.
"International Horticultural Congress," London, 1866, quoted in "Variation
of Animals and Plants," Edition II., Volume II., page 113.) What I meant
in my paper on Linum about plants being dimorphic in function alone, was
that they should be divided into two equal bodies functionally but not
structurally different. I have been much interested by what you say on
seeds which adhere to the valves being rendered conspicuous. You will see
in the new edition of the "Origin" (673/5. "Origin of Species," Edition
IV., 1866, page 238. A discussion on the origin of beauty, including the
bright colours of flowers and fruits.) why I have alluded to the beauty and
bright colours of fruit; after writing this it troubled me that I
remembered to have seen brilliantly coloured seed, and your view occurred
to me. There is a species of peony in which the inside of the pod is
crimson and the seeds dark purple. I had asked a friend to send me some of
these seeds, to see if they were covered with anything which could prove
attractive to birds. I received some seeds the day after receiving your
letter, and I must own that the fleshy covering is so thin that I can
hardly believe it would lead birds to devour them; and so it was in an
analogous case with Passiflora gracilis. How is this in the cases
mentioned by you? The whole case seems to me rather a striking one.

I wish I had heard of Mikania being a leaf-climber before your paper was
printed (673/6. See "Climbing Plants (3rd thousand, 1882), page 116.
Mikania and Mutisia both belong to the Compositae. Mikania scandens is a
twining plant: it is another species which, by its leaf-climbing habit,
supplies a transition to the tendril-climber Mutisia. F. Muller's paper is
in "Linn. Soc. Journ." IX., page 344.), for we thus get a good gradation
from M. scandens to Mutisia, with its little modified, leaf-like tendrils.

I am glad to hear that you can confirm (but render still more wonderful)
Hackel's most interesting case of Linope. Huxley told me that he thought
the case would somehow be explained away.

Down [Received January 24th, 1867].

I have so much to thank you for that I hardly know how to begin. I have
received the bulbils of Oxalis, and your most interesting letter of October
1st. I planted half the bulbs, and will plant the other half in the
spring. The case seems to me very curious, and until trying some
experiments in crossing I can form no conjecture what the abortion of the
stamens in so irregular a manner can signify. But I fear from what you say
the plant will prove sterile, like so many others which increase largely by
buds of various kinds. Since I asked you about Oxalis, Dr. Hildebrand has
published a paper showing that a great number of species are trimorphic,
like Lythrum, but he has tried hardly any experiments. (674/1.
Hildebrand's work, published in the "Monatsb. d. Akad. d. Wiss. Berlin,"
1866, was chiefly on herbarium specimens. His experimental work was
published in the "Bot. Zeitung," 1871.)

I am particularly obliged for the information and specimens of Cordia
(674/2. Cordiaceae: probably dimorphic.), and shall be most grateful for
seed. I have not heard of any dimorphic species in this family. Hardly
anything in your letter interested me so much as your account and drawing
of the valves of the pod of one of the Mimoseae with the really beautiful
seeds. I will send some of these seeds to Kew to be planted. But these
seeds seem to me to offer a very great difficulty. They do not seem hard
enough to resist the triturating power of the gizzard of a gallinaceous
bird, though they must resist that of some other birds; for the skin is as
hard as ivory. I presume that these seeds cannot be covered with any
attractive pulp? I soaked one of the seeds for ten hours in warm water,
which became only very slightly mucilaginous. I think I will try whether
they will pass through a fowl uninjured. (674/3. The seeds proved to be
those of Adenanthera pavonina. The solution of the difficulty is given in
the following extract from a letter to Muller, March 2nd, 1867: "I wrote
to India on the subject, and I hear from Mr. J. Scott that parrots are
eager for the seeds, and, wonderful as the fact is, can split them open
with their beaks; they first collect a large number in their beaks, and
then settle themselves to split them, and in doing so drop many; thus I
have no doubt they are disseminated, on the same principle that the acorns
of our oaks are most widely disseminated." Possibly a similar explanation
may hold good for the brightly coloured seeds of Abrus precatorius.) I
hope you will observe whether any bird devours them; and could you get any
young man to shoot some and observe whether the seeds are found low down in
the intestines? It would be well worth while to plant such seeds with
undigested seeds for comparison. An opponent of ours might make a capital
case against us by saying that here beautiful pods and seeds have been
formed not for the good of the plant, but for the good of birds alone.
These seeds would make a beautiful bracelet for one of my daughters, if I
had enough. I may just mention that Euonymus europoeus is a case in point:
the seeds are coated by a thin orange layer, which I find is sufficient to
cause them to be devoured by birds.

I have received your paper on Martha [Posoqueria (674/4. "Bot. Zeitung,"
1866.)]; it is as wonderful as the most wonderful orchis; Ernst Hackel
brought me the paper and stayed a day with me. I have seldom seen a more
pleasant, cordial, and frank man. He is now in Madeira, where he is going
to work chiefly on the Medusae. His great work is now published, and I
have a copy; but the german is so difficult I can make out but little of
it, and I fear it is too large a work to be translated. Your fact about
the number of seeds in the capsule of the Maxillaria (674/5. See "Animals
and Plants," Edition II., Volume II., page 115.) came just at the right
time, as I wished to give one or two such facts. Does this orchid produce
many capsules? I cannot answer your question about the aerial roots of
Catasetum. I hope you have received the new edition of the "Origin." Your
paper on climbing plants (674/6. "Linn. Soc. Journal," IX., 1867, page
344.) is printed, and I expect in a day or two to receive the spare copies,
and I will send off three copies as before stated, and will retain some in
case you should wish me to send them to any one in Europe, and will
transmit the remainder to yourself.

Down [received February 24th, 1867].

Your letter of November 2nd contained an extraordinary amount of
interesting matter. What a number of dimorphic plants South Brazil
produces: you observed in one day as many or more dimorphic genera than
all the botanists in Europe have ever observed. When my present book is
finished I shall write a final paper upon these plants, so that I am
extremely glad to hear of your observations and to see the dried flowers;
nevertheless, I should regret MUCH if I prevented you from publishing on
the subject. Plumbago (675/1. Plumbago has not been shown to be
dimorphic.) is quite new to me, though I had suspected it. It is curious
how dimorphism prevails by groups throughout the world, showing, as I
suppose, that it is an ancient character; thus Hedyotis is dimorphic in
India (675/2. Hedyotis was sent to Darwin by F. Muller; it seems possible,
therefore, that Hedyotis was written by mistake for some other Rubiaceous
plant, perhaps Oldenlandia, which John Scott sent him from India.); the two
other genera in the same sub-family with Villarsia are dimorphic in Europe
and Ceylon; a sub-genus of Erythroxylon (675/3. No doubt Sethia.) is
dimorphic in Ceylon, and Oxalis with you and at the Cape of Good Hope. If
you can find a dimorphic Oxalis it will be a new point, for all known
species are trimorphic or monomorphic. The case of Convolvulus will be
new, if proved. I am doubtful about Gesneria (675/4. Neither Convolvulus
nor Gesneria have been shown to be dimorphic.), and have been often myself
deceived by varying length of pistil. A difference in the size of the
pollen-grains would be conclusive evidence; but in some cases experiments
by fertilisation can alone decide the point. As yet I know of no case of
dimorphism in flowers which are very irregular; such flowers being
apparently always sufficiently visited and crossed by insects.

Down, April 22nd [1867].

I am very sorry your papers on climbing plants never reached you. They
must be lost, but I put the stamps on myself and I am sure they were right.
I despatched on the 20th all the remaining copies, except one for myself.
Your letter of March 4th contained much interesting matter, but I have to
say this of all your letters. I am particularly glad to hear that Oncidium
flexuosum (676/1. See "Animals and Plants," Edition II., Volume II., page
114. Observations on Oncidium were made by John Scott, and in Brazil by F.
Muller, who "fertilised above one hundred flowers of the above-mentioned
Oncidium flexuosum, which is there endemic, with its own pollen, and with
that taken from distinct plants: all the former were sterile, whilst those
fertilised by pollen from any OTHER PLANT of the same species were
fertile.') is endemic, for I always thought that the cases of self-
sterility with orchids in hot-houses might have been caused by their
unnatural conditions. I am glad, also, to hear of the other analogous
cases, all of which I will give briefly in my book that is now printing.
The lessened number of good seeds in the self-fertilising Epidendrums is to
a certain extent a new case. You suggest the comparison of the growth of
plants produced from self-fertilised and crossed seeds. I began this work
last autumn, and the result, in some cases, has been very striking; but
only, as far as I can yet judge, with exotic plants which do not get freely
crossed by insects in this country. In some of these cases it is really a
wonderful physiological fact to see the difference of growth in the plants
produced from self-fertilised and crossed seeds, both produced by the same
parent-plant; the pollen which has been used for the cross having been
taken from a distinct plant that grew in the same flower-pot. Many thanks
for the dimorphic Rubiaceous plant. Three of your Plumbagos have
germinated, but not as yet any of the Lobelias. Have you ever thought of
publishing a work which might contain miscellaneous observations on all
branches of Natural History, with a short description of the country and of
any excursions which you might take? I feel certain that you might make a
very valuable and interesting book, for every one of your letters is so
full of good observations. Such books, for instance Bates' "Travels on the
Amazons," are very popular in England. I will give your obliging offer
about Brazilian plants to Dr. Hooker, who was to have come here to-day, but
has failed. He is an excellent good fellow, as well as naturalist. He has
lately published a pamphlet, which I think you would like to read; and I
will try and get a copy and send you. (676/2. Sir J.D. Hooker's lecture
on Insular Floras, given before the British Association in August, 1866, is
doubtless referred to. It appeared in the "Gardeners' Chronicle," and was
published as a pamphlet in January, 1867. This fact helps to fix the date
of the present letter.)


(677/1. The following refers to the curious case of Eschscholtzia
described in "Cross and Self-Fertilisation," pages 343-4. The offspring of
English plants after growing for two generations in Brazil became
self-sterile, while the offspring of Brazilian plants became partly
self-fertile in England.)

January 30th [1868].

...The flowers of Eschscholtzia when crossed with pollen from a distinct
plant produced 91 per cent. of capsules; when self-fertilised the flowers
produced only 66 per cent. of capsules. An equal number of crossed and
self-fertilised capsules contained seed by weight in the proportion of 100
to 71. Nevertheless, the self-fertilised flowers produced an abundance of
seed. I enclose a few crossed seeds in hopes that you will raise a plant,
cover it with a net, and observe whether it is self-fertile; at the same
time allowing several uncovered plants to produce capsules, for the
sterility formerly observed by you seems to me very curious.

Down, November 28th [1868].

You end your letter of September 9th by saying that it is a very dull one;
indeed, you make a very great mistake, for it abounds with interesting
facts and thoughts. Your account of the tameness of the birds which
apparently have wandered from the interior, is very curious. But I must
begin on another subject: there has been a great and very vexatious, but
unavoidable delay in the publication of your book. (678/1. "Facts and
Arguments for Darwin," 1869, a translation by the late Mr. Dallas of F.
Muller's "Fur Darwin," 1864: see Volume I., Letter 227.) Prof. Huxley
agrees with me that Mr. Dallas is by far the best translator, but he is
much overworked and had not quite finished the translation about a
fortnight ago. He has charge of the Museum at York, and is now trying to
get the situation of Assistant Secretary at the Geological Society; and all
the canvassing, etc., and his removal, if he gets the place, will, I fear,
cause more than a month's delay in the completion of the translation; and
this I very much regret.

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.

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

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.

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.

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.

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).)

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.)

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.

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.


(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.

In one of two species of Phyllanthus, growing as weeds near my house, the
leaves of the erect branches bend upwards at night, while in the second
species, with horizontal branches, they sleep like those of Phyllanthus
Niruri or of Cassia. In this second species the tips of the branches also
are curled downwards at night, by which movement the youngest leaves are
yet better protected. From their vertical nyctitropic position the leaves
of this Phyllanthus might return to horizontality, traversing 90 deg, in
two ways, either to their own or to the opposite side of the branch; on the
latter way no rotation would be required, while on the former each leaf
must rotate on its own axis in order that its upper surface may be turned
upwards. Thus the way to the wrong side appears to be even less
troublesome. And indeed, in some rare cases I have seen three, four or
even almost all the leaves of one side of a branch horizontally expanded on
the opposite side, with their upper surfaces closely appressed to the lower
surfaces of the leaves of that side.

This Phyllanthus agrees with Cassia not only in its manner of sleeping, but
also by its leaves being paraheliotropic. (687/2. Paraheliotropism is the
movement by which some leaves temporarily direct their edges to the source
of light. See "Movements of Plants," page 445.) Like those of some
Cassiae its leaves take an almost perfectly vertical position, when at
noon, on a summer day, the sun is nearly in the zenith; but I doubt whether
this paraheliotropism will be observable in England. To-day, though
continuing to be fully exposed to the sun, at 3 p.m. the leaves had already
returned to a nearly horizontal position. As soon as there are ripe seeds
I will send you some; of our other species of Phyllanthus I enclose a few
seeds in this letter.

In several species of Hedychium the lateral halves of the leaves when
exposed to bright sunshine, bend downwards so that the lateral margins
meet. It is curious that a hybrid Hedychium in my garden shows scarcely
any trace of this paraheliotropism, while both the parent species are very

Might not the inequality of the cotyledons of Citrus and of Pachira be
attributed to the pressure, which the several embryos enclosed in the same
seed exert upon each other? I do not know Pachira aquatica, but [in] a
species, of which I have a tree in my garden, all the seeds are
polyembryonic, and so were almost all the seeds of Citrus which I examined.
With Coffea arabica also seeds including two embryos are not very rare; but
I have not yet observed whether in this case the cotyledons be inequal.

I repeated to-day Duval-Jouve's measurements on Bryophyllum calycinum
(687/3. "Power of Movement in Plants," page 237. F. Muller's measurements
show, however, that there is a tendency in the leaves to be more highly
inclined at night than in the middle of the day, and so far they agree with
Duval-Jouve's results.); but mine did not agree with his; they are as

Distances in mm. between the tips of the upper pair of leaves.

January 9th, 1881 3 A.M. 1 P.M. 6 P.M.
1st plant 54 43 36
2nd plant 28 25 23
3rd plant 28 27 27
4th plant 51 46 39
5th plant 61 52 45

222 193 170

Down, February 23rd, 1881.

Your letter has interested me greatly, as have so many during many past
years. I thought that you would not object to my publishing in "Nature"
(688/1. "Nature," March 3rd, 1881, page 409.) some of the more striking
facts about the movements of plants, with a few remarks added to show the
bearing of the facts. The case of the Phyllanthus (688/2. See Letter
687.), which turns up its leaves on the wrong side, is most extraordinary
and ought to be further investigated. Do the leaflets sleep on the
following night in the usual manner? Do the same leaflets on successive
nights move in the same strange manner? I was particularly glad to hear of
the strongly marked cases of paraheliotropism. I shall look out with much
interest for the publication about the figs. (688/3. F. Muller published
on Caprification in "Kosmos," 1882.) The creatures which you sketch are
marvellous, and I should not have guessed that they were hymenoptera.
Thirty or forty years ago I read all that I could find about caprification,
and was utterly puzzled. I suggested to Dr. Cruger in Trinidad to
investigate the wild figs, in relation to their cross-fertilisation, and
just before he died he wrote that he had arrived at some very curious
results, but he never published, as I believe, on the subject.

I am extremely glad that the inundation did not so greatly injure your
scientific property, though it would have been a real pleasure to me to
have been allowed to have replaced your scientific apparatus. (688/4. See
Letter 687.) I do not believe that there is any one in the world who
admires your zeal in science and wonderful powers of observation more than
I do. I venture to say this, as I feel myself a very old man, who probably
will not last much longer.

P.S.--With respect to Phyllanthus, I think that it would be a good
experiment to cut off most of the leaflets on one side of the petiole, as
soon as they are asleep and vertically dependent; when the pressure is thus
removed, the opposite leaflets will perhaps bend beyond their vertically
dependent position; if not, the main petiole might be a little twisted so
that the upper surfaces of the dependent and now unprotected leaflets
should face obliquely the sky when the morning comes. In this case
diaheliotropism would perhaps conquer the ordinary movements of the leaves
when they awake, and [assume] their diurnal horizontal position. As the
leaflets are alternate, and as the upper surface will be somewhat exposed
to the dawning light, it is perhaps diaheliotropism which explains your
extraordinary case.

Down, April 12th, 1881.

I have delayed answering your last letter of February 25th, as I was just
sending to the printers the MS. of a very little book on the habits of
earthworms, of which I will of course send you a copy when published. I
have been very much interested by your new facts on paraheliotropism, as I
think that they justify my giving a name to this kind of movement, about
which I long doubted. I have this morning drawn up an account of your
observations, which I will send in a few days to "Nature." (689/1.
"Nature," 1881, page 603. Curious facts are given on the movements of
Cassia, Phyllanthus, sp., Desmodium sp. Cassia takes up a sunlight
position unlike its own characteristic night-position, but resembling
rather that of Haematoxylon (see "Power of Movement," figure 153, page
369). One species of Phyllanthus takes up in sunshine the nyctitropic
attitude of another species. And the same sort of relation occurs in the
genus Bauhinia.) I have thought that you would not object to my giving
precedence to paraheliotropism, which has been so little noticed. I will
send you a copy of "Nature" when published. I am glad that I was not in
too great a hurry in publishing about Lagerstroemia. (689/2.
Lagerstraemia was doubtfully placed among the heterostyled plants ("Forms
of Flowers," page 167). F. Muller's observations showed that a totally
different interpretation of the two sizes of stamen is possible. Namely,
that one set serves merely to attract pollen-collecting bees, who in the
act of visiting the flowers transfer the pollen of the longer stamens to
other flowers. A case of this sort in Heeria, a Melastomad, was described
by Muller ("Nature," August 4th, 1881, page 308), and the view was applied
to the cases of Lagerstroemia and Heteranthera at a later date ("Nature,"
1883, page 364). See Letters 620-30.) I have procured some plants of
Melastomaceae, but I fear that they will not flower for two years, and I
may be in my grave before I can repeat my trials. As far as I can
imperfectly judge from my observations, the difference in colour of the
anthers in this family depends on one set of anthers being partially
aborted. I wrote to Kew to get plants with differently coloured anthers,
but I learnt very little, as describers of dried plants do not attend to
such points. I have, however, sowed seeds of two kinds, suggested to me as
probable. I have, therefore, been extremely glad to receive the seeds of
Heteranthera reniformis. As far as I can make out it is an aquatic plant;
and whether I shall succeed in getting it to flower is doubtful. Will you
be so kind as to send me a postcard telling me in what kind of station it
grows. In the course of next autumn or winter, I think that I shall put
together my notes (if they seem worth publishing) on the use or meaning of
"bloom" (689/3. See Letters 736-40.), or the waxy secretion which makes
some leaves glaucous. I think that I told you that my experiments had led
me to suspect that the movement of the leaves of Mimosa, Desmodium and
Cassia, when shaken and syringed, was to shoot off the drops of water. If
you are caught in heavy rain, I should be very much obliged if you would
keep this notion in your mind, and look to the position of such leaves.
You have such wonderful powers of observation that your opinion would be
more valued by me than that of any other man. I have among my notes one
letter from you on the subject, but I forget its purport. I hope, also,
that you may be led to follow up your very ingenious and novel view on the
two-coloured anthers or pollen, and observe which kind is most gathered by

[Patterdale], June 21st, 1881.

I should be much obliged if you could without much trouble send me seeds of
any heterostyled herbaceous plants (i.e. a species which would flower
soon), as it would be easy work for me to raise some illegitimate seedlings
to test their degree of infertility. The plant ought not to have very
small flowers. I hope that you received the copies of "Nature," with
extracts from your interesting letters (690/1. "Nature," March 3rd, 1881,
Volume XXIII., page 409, contains a letter from C. Darwin on "Movements of
Plants," with extracts from Fritz Muller's letter. Another letter, "On the
Movements of Leaves," was published in "Nature," April 28th, 1881, page
603, with notes on leaf-movements sent to Darwin by Muller.), and I was
glad to see a notice in "Kosmos" on Phyllanthus. (690/2. "Verirrte
Blatter," by Fritz Muller ("Kosmos," Volume V., page 141, 1881). In this
article an account is given of a species of Phyllanthus, a weed in Muller's
garden. See Letter 687.) I am writing this note away from my home, but
before I left I had the satisfaction of seeing Phyllanthus sleeping. Some
of the seeds which you so kindly sent me would not germinate, or had not
then germinated. I received a letter yesterday from Dr. Breitenbach, and
he tells me that you lost many of your books in the desolating flood from
which you suffered. Forgive me, but why should you not order, through your
brother Hermann, books, etc., to the amount of 100 pounds, and I would send
a cheque to him as soon as I heard the exact amount? This would be no
inconvenience to me; on the contrary, it would be an honour and lasting
pleasure to me to have aided you in your invaluable scientific work to this
small and trifling extent. (690/3. See Letter 687, also "Life and
Letters," III., page 242.)


(691/1. The following extract from a letter to F. Muller shows what was
the nature of Darwin's interest in the effect of carbonate of ammonia on
roots, etc. He was, we think, wrong in adhering to the belief that the
movements of aggregated masses are of an amoeboid nature. The masses
change shape, just as clouds do under the moulding action of the wind. In
the plant cell the moulding agent is the flowing protoplasm, but the masses
themselves are passive.)

September 10th, 1881.

Perhaps you may remember that I described in "Insectivorous Plants" a
really curious phenomenon, which I called the aggregation of the protoplasm
in the cells of the tentacles. None of the great German botanists will
admit that the moving masses are composed of protoplasm, though it is
astonishing to me that any one could watch the movement and doubt its
nature. But these doubts have led me to observe analogous facts, and I
hope to succeed in proving my case.

Down, November 13th, 1881.

I received a few days ago a small box (registered) containing dried
flower-heads with brown seeds somewhat sculptured on the sides. There was
no name, and I should be much obliged if some time you would tell me what
these seeds are. I have planted them.

I sent you some time ago my little book on earthworms, which, though of no
importance, has been largely read in England. I have little or nothing to
tell you about myself. I have for a couple of months been observing the
effects of carbonate of ammonia on chlorophyll and on the roots of certain
plants (692/1. Published under the title "The Action of Carbonate of
Ammonia on the Roots of Certain Plants and on Chlorophyll Bodies," "Linn.
Soc. Journ." XIX., 1882, pages 239-61, 262-84.), but the subject is too
difficult for me, and I cannot understand the meaning of some strange facts
which I have observed. The mere recording new facts is but dull work.

Professor Wiesner has published a book (692/2. See Letter 763.), giving a
different explanation to almost every fact which I have given in my "Power
of Movement in Plants." I am glad to say that he admits that almost all my
statements are true. I am convinced that many of his interpretations of
the facts are wrong, and I am glad to hear that Professor Pfeffer is of the
same opinion; but I believe that he is right and I wrong on some points. I
have not the courage to retry all my experiments, but I hope to get my son
Francis to try some fresh ones to test Wiesner's explanations. But I do
not know why I have troubled you with all this.

[4, Bryanston Street], December 19th, 1881.

I hope that you may find time to go on with your experiments on such plants
as Lagerstroemia, mentioned in your letter of October 29th, for I believe
you will arrive at new and curious results, more especially if you can
raise two sets of seedlings from the two kinds of pollen.

Many thanks for the facts about the effect of rain and mud in relation to
the waxy secretion. I have observed many instances of the lower side being
protected better than the upper side, in the case, as I believe, of bushes
and trees, so that the advantage in low-growing plants is probably only an
incidental one. (693/1. The meaning is here obscure: it appears to us
that the significance of bloom on the lower surface of the leaves of both
trees and herbs depends on the frequency with which all or a majority of
the stomata are on the lower surface--where they are better protected from
wet (even without the help of bloom) than on the exposed upper surface. On
the correlation between bloom and stomata, see Francis Darwin "Linn. Soc.
Journ." XXII., page 99.) As I am writing away from my home, I have been
unwilling to try more than one leaf of the Passiflora, and this came out of
the water quite dry on the lower surface and quite wet on the upper. I
have not yet begun to put my notes together on this subject, and do not at
all know whether I shall be able to make much of it. The oddest little
fact which I have observed is that with Trifolium resupinatum, one half of
the leaf (I think the right-hand side, when the leaf is viewed from the
apex) is protected by waxy secretion, and not the other half (693/2. In
the above passage "leaf" should be "leaflet": for a figure of Trifolium
resupinatum see Letter 740.); so that when the leaf is dipped into water,
exactly half the leaf comes out dry and half wet. What the meaning of this
can be I cannot even conjecture. I read last night your very interesting
article in "Kosmos" on Crotalaria, and so was very glad to see the dried
leaves sent by you: it seems to me a very curious case. I rather doubt
whether it will apply to Lupinus, for, unless my memory deceives me, all
the leaves of the same plant sometimes behaved in the same manner; but I
will try and get some of the same seeds of the Lupinus, and sow them in the
spring. Old age, however, is telling on me, and it troubles me to have
more than one subject at a time on hand.

(693/3. In a letter to F. Muller (September 10, 1881) occurs a sentence
which may appropriately close this series: "I often feel rather ashamed of
myself for asking for so many things from you, and for taking up so much of
your valuable time, but I can assure you that I feel grateful.")


Down, April 22nd, 1868.

I have been extremely much pleased by your letter, and I take it as a very
great compliment that you should have written to me at such length...I am

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