More Letters of Charles Darwin Volume II

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Thanks for your comforting sentence about the accursed ducts (accursed
though they be, I should like nothing better than to work at them in the
allied orders, if I had time). I shall be ready for press in three or four
weeks, and have got all my woodcuts drawn. I fear much that publishing
separately will prove a foolish job, but I do not care much, and the work
has greatly amused me. The Catasetum has not flowered yet!

In writing to Lindley about an orchid which he sent me, I told him a little
about Acropera, and in answer he suggests that Gongora may be its female.
He seems dreadfully busy, and I feel that I have more right to kill you
than to kill him; so can you send me one or at most two dried flowers of
Gongora? if you know the habitat of Acropera luteola, a Gongora from the
same country would be the best, but any true Gongora would do; if its
pollen should prove as rudimentary as that of Monacanthus relatively to
Catasetum, I think I could easily perceive it even in dried specimens when
well soaked.

I have picked a little out of Lecoq, but it is awful tedious hunting.

Bates is getting on with his natural history travels in one volume.
(609/4. H.W. Bates, the "Naturalist on the Amazons," 1863. See Volume I.,
Letters 123, 148, also "Life and Letters," Volume II., page 381.) I have
read the first chapter in MS., and I think it will be an excellent book and
very well written; he argues, in a good and new way to me, that tropical
climate has very little direct relation to the gorgeous colouring of
insects (though of course he admits the tropics have a far greater number
of beautiful insects) by taking all the few genera common to Britain and
Amazonia, and he finds that the species proper to the latter are not at all
more beautiful. I wonder how this is in species of the same restricted
genera of plants.

If you can remember it, thank Bentham for getting my Primula paper printed
so quickly. I do enjoy getting a subject off one's hands completely.

I have now got dimorphism in structure in eight natural orders just like
Primula. Asa Gray sent me dried flowers of a capital case in Amsinkia
spectabilis, one of the Boragineae. I suppose you do not chance to have
the plant alive at Kew.

LETTER 610. TO A.G. MORE.
Down, June 7th, 1862.

If you are well and have leisure, will you kindly give me one bit of
information: Does Ophrys arachnites occur in the Isle of Wight? or do the
intermediate forms, which are said to connect abroad this species and the
bee-orchis, ever there occur?

Some facts have led me to suspect that it might just be possible, though
improbable in the highest degree, that the bee [orchis] might be the
self-fertilising form of O. arachnites, which requires insects' aid,
something [in the same way] as we have self-fertilising flowers of the
violet and others requiring insects. I know the case is widely different,
as the bee is borne on a separate plant and is incomparably commoner. This
would remove the great anomaly of the bee being a perpetual self-
fertiliser. Certain Malpighiaceae for years produce only one of the two
forms. What has set my head going on this is receiving to-day a bee having
one alone of the best marked characters of O. arachnites. (610/1. Ophrys
arachnites is probably more nearly allied to O. aranifera than to O.
apifera. For a case somewhat analogous to that suggested see the
description of O. scolopax in "Fertilisation of Orchids," Edition II., page
52.) Pray forgive me troubling you.

LETTER 611. TO G. BENTHAM.
Down, June 22nd [1862?].

Here is a piece of presumption! I must think that you are mistaken in
ranking Hab[enaria] chlorantha (611/1. In Hooker's "Students' Flora,"
1884, page 395, H. chlorantha is given as a subspecies of H. bifolia. Sir
J.D. Hooker adds that they are "according to Darwin, distinct, and require
different species of moths to fertilise them. They vary in the position
and distances of their anther-cells, but intermediates occur." See
"Fertilisation of Orchids," Edition II., page 73.) as a variety of H.
bifolia; the pollen-masses and stigma differ more than in most of the best
species of Orchis. When I first examined them I remember telling Hooker
that moths would, I felt sure, fertilise them in a different manner; and I
have just had proof of this in a moth sent me with the pollinia (which can
be easily recognised) of H. chlorantha attached to its proboscis, instead
of to the sides of its face, as an H. bifolia.

Forgive me scribbling this way; but when a man gets on his hobby-horse he
always is run away with. Anyhow, nothing here requires any answer.

LETTER 612. TO J.D. HOOKER.
Down, [September] 14th [1862].

Your letter is a mine of wealth, but first I must scold you: I cannot
abide to hear you abuse yourself, even in joke, and call yourself a stupid
dog. You, in fact, thus abuse me, because for long years I have looked up
to you as the man whose opinion I have valued more on any scientific
subject than any one else in the world. I continually marvel at what you
know, and at what you do. I have been looking at the "Genera" (612/1.
"Genera Plantarum," by Bentham and Hooker, Volume I., Part I., 1862.), and
of course cannot judge at all of its real value, but I can judge of the
amount of condensed facts under each family and genus.

I am glad you know my feeling of not being able to judge about one's own
work; but I suspect that you have been overworking. I should think you
could not give too much time to Wellwitchia (I spell it different every
time I write it) (612/2. "On Welwitschia," "Linn. Soc. Trans." [1862],
XXIV., 1863.); at least I am sure in the animal kingdom monographs cannot
be too long on the osculant groups.

Hereafter I shall be excessively glad to read a paper about Aldrovanda
(612/3. See "Insectivorous Plants," page 321.), and am very much obliged
for reference. It is pretty to see how the caught flies support Drosera;
nothing else can live.

Thanks about plants with two kinds of anthers. I presume (if an included
flower was a Cassia) (612/4. Todd has described a species of Cassia with
an arrangement of stamens like the Melastomads. See Chapter 2.X.II.) that
Cassia is like lupines, but with some stamens still more rudimentary. If I
hear I will return the three Melastomads; I do not want them, and, indeed,
have cuttings. I am very low about them, and have wasted enormous labour
over them, and cannot yet get a glimpse of the meaning of the parts. I
wish I knew any botanical collector to whom I could apply for seeds in
their native land of any Heterocentron or Monochoetum; I have raised plenty
of seedlings from your plants, but I find in other cases that from a
homomorphic union one generally gets solely the parent form. Do you chance
to know of any botanical collector in Mexico or Peru? I must not now
indulge myself with looking after vessels and homologies. Some future time
I will indulge myself. By the way, some time I want to talk over the
alternation of organs in flowers with you, for I think I must have quite
misunderstood you that it was not explicable.

I found out the Verbascum case by pure accident, having transplanted one
for experiment, and finding it to my astonishment utterly sterile. I
formerly thought with you about rarity of natural hybrids, but I am
beginning to change: viz., oxlips (not quite proven), Verbascum, Cistus
(not quite proven), Aegilops triticoides (beautifully shown by Godron),
Weddell's and your orchids (612/5. For Verbascum see "Animals and Plants,"
Edition II., Volume I., page 356; for Cistus, Ibid., Edition II., Volume
I., page 356, Volume II., page 122; for Aegilops, Ibid., Edition II.,
Volume I., page 330, note.), and I daresay many others recorded. Your
letters are one of my greatest pleasures in life, but I earnestly beg you
never to write unless you feel somewhat inclined, for I know how hard you
work, as I work only in the morning it is different with me, and is only a
pleasant relaxation. You will never know how much I owe to you for your
constant kindness and encouragement.

LETTER 613. TO JOHN LUBBOCK (Lord Avebury).
Cliff Cottage, Bournemouth, Hants, September 2nd [1862].

Hearty thanks for your note. I am so glad that your tour answered so
splendidly. My poor patients (613/1. Mrs. Darwin and one of her sons,
both recovering from scarlet fever.) got here yesterday, and are doing
well, and we have a second house for the well ones. I write now in great
haste to beg you to look (though I know how busy you are, but I cannot
think of any other naturalist who would be careful) at any field of common
red clover (if such a field is near you) and watch the hive-bees: probably
(if not too late) you will see some sucking at the mouth of the little
flowers and some few sucking at the base of the flowers, at holes bitten
through the corollas. All that you will see is that the bees put their
heads deep into the [flower] head and rout about. Now, if you see this, do
for Heaven's sake catch me some of each and put in spirits and keep them
separate. I am almost certain that they belong to two castes, with long
and short proboscids. This is so curious a point that it seems worth
making out. I cannot hear of a clover field near here.

LETTER 614. TO JOHN LUBBOCK (Lord Avebury).
Cliff Cottage, Bournemouth, Wednesday, September 3rd [1862].

I beg a million pardons. Abuse me to any degree, but forgive me: it is
all an illusion (but almost excusable) about the bees. (614/1. H. Muller,
"Fertilisation of Flowers," page 186, describes hive-bees visiting
Trifolium pratense for the sake of the pollen. Darwin may perhaps have
supposed that these were the variety of bees whose proboscis was long
enough to reach the nectar. In "Cross and Self Fertilisation," page 361,
Darwin describes hive-bees apparently searching for a secretion on the
calyx. In the same passage in "Cross and Self Fertilisation" he quotes
Muller as stating that hive-bees obtain nectar from red clover by breaking
apart the petals. This seems to us a misinterpretation of the "Befruchtung
der Blumen," page 224.) I do so hope that you have not wasted any time
from my stupid blunder. I hate myself, I hate clover, and I hate bees.

(FIGURE 10.--DIAGRAM OF CRUCIFEROUS FLOWER.

FIGURE 11.--DISSECTION OF CRUCIFEROUS FLOWER.

Laid flat open, showing by dotted lines the course of spiral vessels in all
the organs; sepals and petals shown on one side alone, with the stamens on
one side above with course of vessels indicated, but not prolonged. Near
side of pistil with one spiral vessel cut away.)

LETTER 615. TO J.D. HOOKER.
Cliff Cottage, Bournemouth, September 11th, 1862.

You once told me that Cruciferous flowers were anomalous in alternation of
parts, and had given rise to some theory of dedoublement.

Having nothing on earth to do here, I have dissected all the spiral vessels
in a flower, and instead of burning my diagrams [Figures 10 and 11], I send
them to you, you miserable man. But mind, I do not want you to send me a
discussion, but just some time to say whether my notions are rubbish, and
then burn the diagrams. It seems to me that all parts alternate
beautifully by fours, on the hypothesis that two short stamens of outer
whorl are aborted (615/1. The view given by Darwin is (according to
Eichler) that previously held by Knuth, Wydler, Chatin, and others.
Eichler himself believes that the flower is dimerous, the four longer
stamens being produced by the doubling or splitting of the upper (i.e.
antero-posterior) pair of stamens. If this view is correct, and there are
good reasons for it, it throws much suspicion on the evidence afforded by
the course of vessels, for there is no trace of the common origin of the
longer stamens in the diagram (Figure 11). Again, if Eichler is right, the
four vessels shown in the section of the ovary are misleading. Darwin
afterwards gave a doubtful explanation of this, and concluded that the
ovary is dimerous. See Letter 616.); and this view is perhaps supported by
their being so few, only two sub-bundles in the two lateral main bundles,
where I imagine two short stamens have aborted, but I suppose there is some
valid objection against this notion. The course of the side vessels in the
sepals is curious, just like my difficulty in Habenaria. (615/2. See
Letter 605.) I am surprised at the four vessels in the ovarium. Can this
indicate four confluent pistils? anyhow, they are in the right alternating
position. The nectary within the base of the shorter stamens seems to
cause the end sepals apparently, but not really, to arise beneath the
lateral sepals.

I think you will understand my diagrams in five minutes, so forgive me for
bothering you. My writing this to you reminds me of a letter which I
received yesterday from Claparede, who helped the French translatress of
the "Origin" (615/3. The late Mlle. Royer.), and he tells me he had
difficulty in preventing her (who never looked at a bee's cell) from
altering my whole description, because she affirmed that an hexagonal prism
must have an hexagonal base! Almost everywhere in the "Origin," when I
express great doubt, she appends a note explaining the difficulty, or
saying that there is none whatever!! (615/4. See "Life and Letters," II.,
page 387.) It is really curious to know what conceited people there are in
the world (people, for instance, after looking at one Cruciferous flower,
explain their homologies).

This is a nice, but most barren country, and I can find nothing to look at.
Even the brooks and ponds produce nothing. The country is like Patagonia.
my wife is almost well, thank God, and Leonard is wonderfully improved
...Good God, what an illness scarlet fever is! The doctor feared rheumatic
fever for my wife, but she does not know her risk. It is now all over.

(FIGURE 12.)

LETTER 616. TO J.D. HOOKER.
Cliff Cottage, Bournemouth, Thursday Evening [September 18th, 1862].

Thanks for your pleasant note, which told me much news, and upon the whole
good, of yourselves. You will be awfully busy for a time, but I write now
to say that if you think it really worth while to send me a few Dielytra,
or other Fumariaceous plant (which I have already tried in vain to find
here) in a little tin box, I will try and trace the vessels; but please
observe, I do not know that I shall have time, for I have just become
wonderfully interested in experimenting on Drosera with poisons, etc. If
you send any Fumariaceous plant, send if you can, also two or three single
balsams. After writing to you, I looked at vessels of ovary of a
sweet-pea, and from this and other cases I believe that in the ovary the
midrib vessel alone gives homologies, and that the vessels on the edge of
the carpel leaf often run into the wrong bundle, just like those on the
sides of the sepals. Hence I [suppose] in Crucifers that the ovarium
consists of two pistils; AA [Figure 12] being the midrib vessels, and BB
being those formed of the vessels on edges of the two carpels, run
together, and going to wrong bundles. I came to this conclusion before
receiving your letter.

I wonder why Asa Gray will not believe in the quaternary arrangement; I had
fancied that you saw some great difficulty in the case, and that made me
think that my notion must be wrong.

LETTER 617. TO J.D. HOOKER.
Down, September 27th [1862].

Masdevallia turns out nothing wonderful (617/1. This may refer to the
homologies of the parts. He was unable to understand the mechanism of the
flower.--"Fertilisation of Orchids," Edition II., page 136.); I was merely
stupid about it; I am not the less obliged for its loan, for if I had lived
till 100 years old I should have been uneasy about it. It shall be
returned the first day I send to Bromley. I have steamed the other plants,
and made the sensitive plant very sensitive, and shall soon try some
experiments on it. But after all it will only be amusement. Nevertheless,
if not causing too much trouble, I should be very glad of a few young
plants of this and Hedysarum in summer (617/2. Hedysarum or Desmodium
gyrans, the telegraph-plant.), for this kind of work takes no time and
amuses me much. Have you seeds of Oxalis sensitiva, which I see mentioned
in books? By the way, what a fault it is in Henslow's "Botany" that he
gives hardly any references; he alludes to great series of experiments on
absorption of poison by roots, but where to find them I cannot guess.
Possibly the all-knowing Oliver may know. I can plainly see that the
glands of Drosera, from rapid power (almost instantaneous) of absorption
and power of movement, give enormous advantage for such experiments. And
some day I will enjoy myself with a good set to work; but it will be a
great advantage if I can get some preliminary notion on other sensitive
plants and on roots.

Oliver said he would speak about some seeds of Lythrum hyssopifolium being
preserved for me. By the way, I am rather disgusted to find I cannot
publish this year on Lythrum salicaria; I must make 126 additional crosses.
All that I expected is true, but I have plain indication of much higher
complexity. There are three pistils of different structure and functional
power, and I strongly suspect altogether five kinds of pollen all
different in this one species! (617/3. See "Forms of Flowers," Edition
II., page 138.)

By any chance have you at Kew any odd varieties of the common potato? I
want to grow a few plants of every variety, to compare flowers, leaves,
fruit, etc., as I have done with peas, etc. (617/4. "Animals and Plants,"
Edition II., Volume I., page 346. Compare also the similar facts with
regard to cabbages, loc. cit., page 342. Some of the original specimens
are in the Botanical Museum at Cambridge.)

LETTER 618. J.D. HOOKER TO CHARLES DARWIN.

(618/1. The following is part of Letter 144, Volume I. It refers to
reviews of "Fertilisation of Orchids" in the "Gardeners' Chronicle," 1862,
pages 789, 863, 910, and in the "Natural History Review," October, 1862,
page 371.)

November 7th, 1862.

Dear old Darwin,

I assure you it was not my fault! I worried Lindley over and over again to
notice your orchid book in the "Chronicle" by the very broadest hints man
could give. (618/2. See "Life and Letters," III., page 273.) At last he
said, "really I cannot, you must do it for me," and so I did--volontiers.
Lindley felt that he ought to have done it himself, and my main effort was
to write it "a la Lindley," and in this alone I have succeeded--that people
all think it is exactly Lindley's style!!! which diverts me vastly. The
fact is, between ourselves, I fear that poor L. is breaking up--he said
that he could not fix his mind on your book. He works himself beyond his
mental or physical powers.

And now, my dear Darwin, I may as well make a clean breast of it, and tell
you that I wrote the "Nat. Hist. Review" notice too--to me a very difficult
task, and one I fancied I failed in, comparatively. Of this you are no
judge, and can be none; you told me to tell Oliver it pleased you, and so I
am content and happy.

LETTER 619. TO W.E. DARWIN.
Down, 4th [about 1862-3?]

I have been looking at the fertilisation of wheat, and I think possibly you
might find something curious. I observed in almost every one of the
pollen-grains, which had become empty and adhered to (I suppose the viscid)
branching hairs of the stigma, that the pollen-tube was always (?) emitted
on opposite side of grain to that in contact with the branch of the stigma.
This seems very odd. The branches of the stigma are very thin, formed
apparently of three rows of cells of hardly greater diameter than pollen-
tube. I am astonished that the tubes should be able to penetrate the
walls. The specimens examined (not carefully by me) had pollen only during
few hours on stigma; and the mere SUSPICION has crossed me that the pollen-
tubes crawl down these branches to the base and then penetrate the
stigmatic tissue. (619/1. See Strasburger's "Neue Untersuchungen uber den
Befruchtungsvorgang bei den Phanerogamen," 1884. In Alopecurus pratensis
he describes the pollen as adhering to the end of a projection from the
stigma where it germinates; the tube crawls along or spirally round this
projection until it reaches the angle where the stigmatic branch is given
off; here it makes an entrance and travels in the middle lamella between
two cells.) The paleae open for a short period for stigma to be dusted,
and then close again, and such travelling down would take place under
protection. High powers and good adjustment are necessary. Ears expel
anthers when kept in water in room; but the paleae apparently do not open
and expose stigma; but the stigma could easily be artificially impregnated.

If I were you I would keep memoranda of points worth attending to.

2.X.II. MELASTOMACEAE, 1862-1881.

(620/1. The following series of letters (620-630) refers to the
Melastomaceae and certain other flowers of analogous form. In 1862 Darwin
attempted to explain the existence of two very different sets of stamens in
these plants as a case of dimorphism, somewhat analogous to the state of
things in Primula. In this view he was probably wrong, but this does not
diminish the interest of the crossing experiments described in the letters.
The persistence of his interest in this part of the subject is shown in the
following passage from his Preface to the English translation of H.
Muller's "Befruchtung der Blumen"; the passage is dated February, 1882, but
was not published until the following year.

"There exist also some few plants the flowers of which include two sets of
stamens, differing in the shape of the anthers and in the colour of the
pollen; and at present no one knows whether this difference has any
functional significance, and this is a point which ought to be determined."

It is not obvious why he spoke of the problem as if no light had been
thrown on it, since in 1881 Fritz Muller had privately (see Letter 629)
offered an explanation which Darwin was strongly inclined to accept.
(620/2. H. Muller published ("Nature," August 4th, 1881) a letter from his
brother Fritz giving the theory in question for Heeria. Todd ("American
Naturalist," April 1882), described a similar state of things in Solanum
rostratum and in Cassia: and H.O. Forbes ("Nature," August 1882, page 386)
has done the same for Melastoma. In Rhexia virginica Mr. W.H. Leggett
("Bulletin Torrey Bot. Club, New York," VIII., 1881, page 102) describes
the curious structure of the anther, which consists of two inflated
portions and a tubular part connecting the two. By pressing with a blunt
instrument on one of the ends, the pollen is forced out in a jet through a
fine pore in the other inflated end. Mr. Leggett has seen bees treading on
the anthers, but could not get near enough to see the pollen expelled. In
the same journal, Volume IX., page 11, Mr. Bailey describes how in
Heterocentron roseum, "upon pressing the bellows-like anther with a blunt
pencil, the pollen was ejected to a full inch in distance." On
Lagerstroemia as comparable with the Melastomads see Letter 689.) Fritz
Muller's theory with regard to the Melastomads and a number of analogous
cases in other genera are discussed in H. Muller's article in "Kosmos"
(620/3. "Kosmos," XIII., 1883, page 241.), where the literature is given.
F. Muller's theory is that in Heeria the yellow anthers serve merely as a
means of attracting pollen-collecting bees, while the longer stamens with
purple or crimson anthers supply pollen for fertilising purposes. If
Muller is right the pollen from the yellow anthers would not normally reach
the stigma. The increased vigour observed in the seedlings from the yellow
anthers would seem to resemble the good effect of a cross between different
individuals of the same species as worked out in "Cross and Self
Fertilisation," for it is difficult to believe that the pollen of the
purple anthers has become, by adaptation, less effective than that of the
yellow anthers. In the letters here given there is some contradiction
between the statements as to the position of the two sets of stamens in
relation to the sepals. According to Eichler ("Bluthendiagramme, II., page
482) the longer stamens may be either epipetalous or episepalous in this
family.

The work on the Melastomads is of such intrinsic importance that we have
thought it right to give the correspondence in considerable detail; we have
done so in spite of the fact that Darwin arrived at no definite conclusion,
and in spite of an element of confusion and unsatisfactoriness in the
series of letters. This applies also to Letter 629, written after Darwin
had learned Fritz Muller's theory, which is obscured by some errors or
slips of the pen.)

LETTER 620. TO G. BENTHAM.
Down, February 3rd [1862?]

As you so kindly helped me before on dimorphism, will you forgive me
begging for a little further information, if in your power to give it? The
case is that of the Melastomads with eight stamens, on which I have been
experimenting. I am perplexed by opposed statements: Lindley says the
stamens which face the petals are sterile; Wallich says in Oxyspora
paniculata that the stamens which face the sepals are destitute of pollen;
I find plenty of apparently good pollen in both sets of stamens in
Heterocentron [Heeria], Monochoetum, and Centradenia. Can you throw any
light on this? But there is another point on which I am more anxious for
information. Please look at the enclosed miserable diagram. I find that
the pollen of the yellow petal-facing stamens produce more than twice as
much seed as the pollen of the purple sepal-facing stamens. This is
exactly opposed to Lindley's statement--viz., that the petal-facing stamens
are sterile. But I cannot at present believe that the case has any
relation to abortion; it is hardly possible to believe that the longer and
very curious stamens, which face the sepals in this Heterocentron, are
tending to be rudimentary, though their pollen applied to their own flowers
produces so much less seed. It is conformable with what we see in Primula
that the [purple] sepal-facing anthers, which in the plant seen by me stood
quite close on each side of the stigma, should have been rendered less
fitted to fertilise the stigma than the stamens on the opposite side of the
flower. Hence the suspicion has crossed me that if many plants of the
Heterocentron roseum were examined, half would be found with the pistil
nearly upright, instead of being rectangularly bent down, as shown in the
diagram (620/4. According to Willis, "Flowering Plants and Ferns," 1897,
Volume II., page 252, the style in Monochoetum, "at first bent downwards,
moves slowly up till horizontal."); or, if the position of pistil is fixed,
that in half the plants the petal-facing stamens would bend down, and in
the other half of the plants the sepal-facing stamens would bend down as in
the diagram. I suspect the former case, as in Centradenia I find the
pistil nearly straight. Can you tell me? (620/5. No reply by Mr. Bentham
to this or the following queries has been found.) Can the name
Heterocentron have any reference to such diversity? Would it be asking too
great a favour to ask you to look at dried specimens of Heterocentron
roseum (which would be best), or of Monochoetum, or any eight-stamened
Melastomad, of which you have specimens from several localities (as this
would ensure specimens having been taken from distinct plants), and observe
whether the pistil bends differently or stamens differently in different
plants? You will at once see that, if such were the fact, it would be a
new form of dimorphism, and would open up a large field of inquiry with
respect to the potency of the pollen in all plants which have two sets of
stamens--viz., longer and shorter. Can you forgive me for troubling you at
such unreasonable length? But it is such waste of time to experiment
without some guiding light. I do not know whether you have attended
particularly to Melastoma; if you have not, perhaps Hooker or Oliver may
have done so. I should be very grateful for any information, as it will
guide future experiments.