_Climbing Plants; Power of Movement in Plants; Insectivorous
Plants; Kew Index of Plant Names._
My father mentions in his _Autobiography_ (p. 45) that he was led to
take up the subject of climbing plants by reading Dr. Gray's paper,
"Note on the Coiling of the Tendrils of Plants."[290] This essay seems
to have been read in 1862, but I am only able to guess at the date of
the letter in which he asks for a reference to it, so that the precise
date of his beginning this work cannot be determined.
In June 1863, he was certainly at work, and wrote to Sir J. D. Hooker
for information as to previous publications on the subject, being then
in ignorance of Palm's and H. v. Mohl's works on climbing plants, both
of which were published in 1827.
_C. Darwin to Asa Gray._ Down, August 4 [1863].
My present hobby-horse I owe to you, viz. the tendrils: their
irritability is beautiful, as beautiful in all its modifications as
anything in Orchids. About the _spontaneous_ movement (independent of
touch) of the tendrils and upper internodes, I am rather taken aback by
your saying, "is it not well known?" I can find nothing in any book
which I have.... The spontaneous movement of the tendrils is independent
of the movement of the upper internodes, but both work harmoniously
together in sweeping a circle for the tendrils to grasp a stick. So with
all climbing plants (without tendrils) as yet examined, the upper
internodes go on night and day sweeping a circle in one fixed direction.
It is surprising to watch the Apocyneae with shoots 18 inches long
(beyond the supporting stick), steadily searching for something to climb
up. When the shoot meets a stick, the motion at that point is arrested,
but in the upper part is continued; so that the climbing of all plants
yet examined is the simple result of the spontaneous circulatory
movement of the upper internodes.[291] Pray tell me whether anything has
been published on this subject? I hate publishing what is old; but I
shall hardly regret my work if it is old, as it has much amused me....
He soon found that his observations were not entirely novel, and wrote
to Hooker: "I have now 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. It is strange, but I really think no one has
explained simple twining plants. These books have stirred me up, and
made me wish for plants specified in them."
He continued his observations on climbing plants during the prolonged
illness from which he suffered in the autumn of 1863, and in the
following spring. He wrote to Sir J. D. Hooker, apparently in March
1864:--
"The hot-house is such an amusement to me, and my amusement I owe to
you, as my delight is to look at the many odd leaves and plants from
Kew.... The only approach to work which I can do is to look at tendrils
and climbers, this does not distress my weakened brain. Ask Oliver to
look over the enclosed queries (and do you look) and amuse a broken-down
brother naturalist by answering any which he can. If you ever lounge
through your houses, remember me and climbing plants."
A letter to Dr. Gray, April 9, 1865, has a word or two on the subject.--
"I have began correcting proofs of my paper on Climbing Plants. I
suppose I shall be able to send you a copy in four or five weeks. I
think it contains a good deal new, and some curious points, but it is so
fearfully long, that no one will ever read it. If, however, you do not
_skim_ through it, you will be an unnatural parent, for it is your
child."
Dr. Gray not only read it but approved of it, to my father's great
satisfaction, as the following extracts show:--
"I was much pleased to get your letter of July 24th. Now that I can do
nothing, I maunder over old subjects, and your approbation of my
climbing paper gives me _very_ great satisfaction. I made my
observations when I could do nothing else and much enjoyed it, but
always doubted whether they were worth publishing....
"I received yesterday your article[292] on climbers, and it has pleased
me in an extraordinary and even silly manner. You pay me a superb
compliment, and as I have just said to my wife, I think my friends must
perceive that I like praise, they give me such hearty doses. I always
admire your skill in reviews or abstracts, and you have done this
article excellently and given the whole essence of my paper.... I have
had a letter from a good zoologist in S. Brazil, F. Mueller, who has been
stirred up to observe climbers, and gives me some curious cases of
_branch_-climbers, in which branches are converted into tendrils, and
then continue to grow and throw out leaves and new branches, and then
lose their tendril character."
The paper on Climbing Plants was republished in 1875, as a separate
book. The author had been unable to give his customary amount of care to
the style of the original essay, owing to the fact that it was written
during a period of continued ill-health, and it was now found to require
a great deal of alteration. He wrote to Sir J. D. Hooker (March 3,
1875): "It is lucky for authors in general that they do not require such
dreadful work in merely licking what they write into shape." And to Mr.
Murray, in September, he wrote: "The corrections are heavy in _Climbing
Plants_, and yet I deliberately went over the MS. and old sheets three
times." The book was published in September 1875, an edition of 1500
copies was struck off; the edition sold fairly well, and 500 additional
copies were printed in June of the following year.
_The Power of Movement in Plants._ 1880.
The few sentences in the autobiographical chapter give with sufficient
clearness the connection between the _Power of Movement_ and the book on
Climbing Plants. The central idea of the book is that the movements of
plants in relation to light, gravitation, &c., are modifications of a
spontaneous tendency to revolve or circumnutate, which is widely
inherent in the growing parts of plants. This conception has not been
generally adopted, and has not taken a place among the canons of
orthodox physiology. The book has been treated by Professor Sachs with a
few words of professorial contempt; and by Professor Wiesner it has been
honoured by careful and generously expressed criticism.
Mr. Thiselton Dyer[293] has well said: "Whether this masterly
conception of the unity of what has hitherto seemed a chaos of unrelated
phenomena will be sustained, time alone will show. But no one can doubt
the importance of what Mr. Darwin has done, in showing that for the
future the phenomena of plant movement can and indeed must be studied
from a single point of view."
The work was begun in the summer of 1877, after the publication of
_Different Forms of Flowers_, and by the autumn his enthusiasm for the
subject was thoroughly established, and he wrote to Mr. Dyer: "I am all
on fire at the work." At this time he was studying the movements of
cotyledons, in which the sleep of plants is to be observed in its
simplest form; in the following spring he was trying to discover what
useful purpose those sleep-movements could serve, and wrote to Sir
Joseph Hooker (March 25th, 1878):--
"I think we have _proved_ that the sleep of plants is to lessen the
injury to the leaves from radiation. This has interested me much, and
has cost us great labour, as it has been a problem since the time of
Linnaeus. But we have killed or badly injured a multitude of plants.
N.B.--_Oxalis carnosa_ was most valuable, but last night was killed."
The book was published on November 6, 1880, and 1500 copies were
disposed of at Mr. Murray's sale. With regard to it he wrote to Sir J.
D. Hooker (November 23):--
"Your note has pleased me much--for I did not expect that you would have
had time to read _any_ of it. Read the last chapter, and you will know
the whole result, but without the evidence. The case, however, of
radicles bending after exposure for an hour to geotropism, with their
tips (or brains) cut off is, I think worth your reading (bottom of p.
525); it astounded me. But I will bother you no more about my book. The
sensitiveness of seedlings to light is marvellous."
To another friend, Mr. Thiselton Dyer, he wrote (November 28, 1880):
"Very many thanks for your most kind note, but you think too highly of
our work, not but what this is very pleasant.... Many of the Germans are
very contemptuous about making out the use of organs; but they may sneer
the souls out of their bodies, and I for one shall think it the most
interesting part of Natural History. Indeed you are greatly mistaken if
you doubt for one moment on the very great value of your constant and
most kind assistance to us."
The book was widely reviewed, and excited much interest among the
general public. The following letter refers to a leading article in the
_Times_, November 20, 1880:--
_C. D. to Mrs. Haliburton._[294] Down, November 22, 1880.
MY DEAR SARAH,--You see how audaciously I begin; but I have always loved
and shall ever love this name. Your letter has done more than please me,
for its kindness has touched my heart. I often think of old days and of
the delight of my visits to Woodhouse, and of the deep debt of gratitude
which I owe to your father. It was very good of you to write. I had
quite forgotten my old ambition about the Shrewsbury newspaper;[295] but
I remember the pride which I felt when I saw in a book about beetles the
impressive words "captured by C. Darwin." Captured sounded so grand
compared with caught. This seemed to me glory enough for any man! I do
not know in the least what made the _Times_ glorify me, for it has
sometimes pitched into me ferociously.
I should very much like to see you again, but you would find a visit
here very dull, for we feel very old and have no amusement, and lead a
solitary life. But we intend in a few weeks to spend a few days in
London, and then if you have anything else to do in London, you would
perhaps come and lunch with us.
Believe me, my dear Sarah,
Yours gratefully and affectionately.
The following letter was called forth by the publication of a volume
devoted to the criticism of the _Power of Movement in Plants_ by an
accomplished botanist, Dr. Julius Wiesner, Professor of Botany in the
University of Vienna:
_C. D. to Julius Wiesner._ Down, October 25th, 1881.
MY DEAR SIR,--I have now finished your book,[296] and have understood
the whole except a very few passages. In the first place, let me thank
you cordially for the manner in which you have everywhere treated me.
You have shown how a man may differ from another in the most decided
manner, and yet express his difference with the most perfect courtesy.
Not a few English and German naturalists might learn a useful lesson
from your example; for the coarse language often used by scientific men
towards each other does no good, and only degrades science.
I have been profoundly interested by your book, and some of your
experiments are so beautiful, that I actually felt pleasure while being
vivisected. It would take up too much space to discuss all the important
topics in your book. I fear that you have quite upset the interpretation
which I have given of the effects of cutting off the tips of
horizontally extended roots, and of those laterally exposed to moisture;
but I cannot persuade myself that the horizontal position of lateral
branches and roots is due simply to their lessened power of growth. Nor
when I think of my experiments with the cotyledons of _Phalaris_, can I
give up the belief of the transmission of some stimulus due to light
from the upper to the lower part. At p. 60 you have misunderstood my
meaning, when you say that I believe that the effects from light are
transmitted to a part which is not itself heliotropic. I never
considered whether or not the short part beneath the ground was
heliotropic; but I believe that with young seedlings the part which
bends _near_, but _above_ the ground is heliotropic, and I believe so
from this part bending only moderately when the light is oblique, and
bending rectangularly when the light is horizontal. Nevertheless the
bending of this lower part, as I conclude from my experiments with
opaque caps, is influenced by the action of light on the upper part. My
opinion, however, on the above and many other points, signifies very
little, for I have no doubt that your book will convince most botanists
that I am wrong in all the points on which we differ.
Independently of the question of transmission, my mind is so full of
facts leading me to believe that light, gravity, &c., act not in a
direct manner on growth, but as stimuli, that I am quite unable to
modify my judgment on this head. I could not understand the passage at
p. 78, until I consulted my son George, who is a mathematician. He
supposes that your objection is founded on the diffused light from the
lamp illuminating both sides of the object, and not being reduced, with
increasing distance in the same ratio as the direct light; but he doubts
whether this _necessary_ correction will account for the very little
difference in the heliotropic curvature of the plants in the successive
pots.
With respect to the sensitiveness of the tips of roots to contact, I
cannot admit your view until it is proved that I am in error about bits
of card attached by liquid gum causing movement; whereas no movement
was caused if the card remained separated from the tip by a layer of the
liquid gum. The fact also of thicker and thinner bits of card attached
on opposite sides of the same root by shellac, causing movement in one
direction, has to be explained. You often speak of the tip having been
injured; but externally there was no sign of injury: and when the tip
was plainly injured, the extreme part became curved _towards_ the
injured side. I can no more believe that the tip was injured by the bits
of card, at least when attached by gum-water, than that the glands of
Drosera are injured by a particle of thread or hair placed on it, or
that the human tongue is so when it feels any such object.
About the most important subject in my book, namely circumnutation, I
can only say that I feel utterly bewildered at the difference in our
conclusions; but I could not fully understand some parts which my son
Francis will be able to translate to me when he returns home. The
greater part of your book is beautifully clear.
Finally, I wish that I had enough strength and spirit to commence a
fresh set of experiments, and publish the results, with a full
recantation of my errors when convinced of them; but I am too old for
such an undertaking, nor do I suppose that I shall be able to do much,
or any more, original work. I imagine that I see one possible source of
error in your beautiful experiment of a plant rotating and exposed to a
lateral light.
With high respect, and with sincere thanks for the kind manner in which
you have treated me and my mistakes, I remain,
My dear Sir, yours sincerely.
_Insectivorous Plants._
In the summer of 1860 he was staying at the house of his sister-in-law,
Miss Wedgwood, in Ashdown Forest whence he wrote (July 29, 1860), to Sir
Joseph Hooker:--
"Latterly I have done nothing here; but at first I amused myself with a
few observations on the insect-catching power of Drosera:[297] and I
must consult you some time whether my 'twaddle' is worth communicating
to the Linnean Society."
In August he wrote to the same friend:--
"I will gratefully send my notes on Drosera when copied by my copier:
the subject amused me when I had nothing to do."
He has described in the _Autobiography_ (p. 47), the general nature of
these early experiments. He noticed insects sticking to the leaves, and
finding that flies, &c., placed on the adhesive glands, were held fast
and embraced, he suspected that the captured prey was digested and
absorbed by the leaves. He therefore tried the effect on the leaves of
various nitrogenous fluids--with results which, as far as they went,
verified his surmise. In September, 1860, he wrote to Dr. Gray:--
"I have been infinitely amused by working at Drosera: the movements are
really curious; and the manner in which the leaves detect certain
nitrogenous compounds is marvellous. You will laugh; but it is, at
present, my full belief (after endless experiments) that they detect
(and move in consequence of) the 1/2880 part of a single grain of
nitrate of ammonia; but the muriate and sulphate of ammonia bother their
chemical skill, and they cannot make anything of the nitrogen in these
salts!"
Later in the autumn he was again obliged to leave home for Eastbourne,
where he continued his work on Drosera.
On his return home he wrote to Lyell (November 1860):--
"I will and must finish my Drosera MS., which will take me a week, for,
at the present moment, I care more about Drosera than the origin of all
the species in the world. But I will not publish on Drosera till next
year, for I am frightened and astounded at my results. I declare it is a
certain fact, that one organ is so sensitive to touch, that a weight
seventy-eight-times less than that, viz., 1/1000 of a grain, which will
move the best chemical balance, suffices to cause a conspicuous
movement. Is it not curious that a plant should be far more sensitive to
the touch than any nerve in the human body? Yet I am perfectly sure that
this is true. When I am on my hobby-horse, I never can resist telling my
friends how well my hobby goes, so you must forgive the rider."
The work was continued, as a holiday task, at Bournemouth, where he
stayed during the autumn of 1862.
A long break now ensued in his work on insectivorous plants, and it was
not till 1872 that the subject seriously occupied him again. A passage
in a letter to Dr. Asa Gray, written in 1863 or 1864, shows, however,
that the question was not altogether absent from his mind in the
interim:--
"Depend on it you are unjust on the merits of my beloved Drosera; it is
a wonderful plant, or rather a most sagacious animal. I will stick up
for Drosera to the day of my death. Heaven knows whether I shall ever
publish my pile of experiments on it."
He notes in his diary that the last proof of the _Expression of the
Emotions_ was finished on August 22, 1872, and that he began to work on
Drosera on the following day.
_C. D. to Asa Gray_ [Sevenoaks], October 22 [1872].
... I have worked pretty hard for four or five weeks on Drosera, and
then broke down; so that we took a house near Sevenoaks for three weeks
(where I now am) to get complete rest. I have very little power of
working now, and must put off the rest of the work on Drosera till next
spring, as my plants are dying. It is an endless subject, and I must cut
it short, and for this reason shall not do much on Dionaea. The point
which has interested me most is tracing the _nerves_! which follow the
vascular bundles. By a prick with a sharp lancet at a certain point, I
can paralyse one-half the leaf, so that a stimulus to the other half
causes no movement. It is just like dividing the spinal marrow of a
frog:--no stimulus can be sent from the brain or anterior part of the
spine to the hind legs: but if these latter are stimulated, they move by
reflex action. I find my old results about the astonishing sensitiveness
of the nervous system (!?) of Drosera to various stimulants fully
confirmed and extended....
_C. D. to Asa Gray_, Down, June 3 [1874].
... I am now hard at work getting my book on Drosera & Co. ready for the
printers, but it will take some time, for I am always finding out new
points to observe. I think you will be interested by my observations on
the digestive process in Drosera; the secretion contains an acid of the
acetic series, and some ferment closely analogous to, but not identical
with, pepsine; for I have been making a long series of comparative
trials. No human being will believe what I shall publish about the
smallness of the doses of phosphate of ammonia which act....
The manuscript of _Insectivorous Plants_ was finished in March 1875. He
seems to have been more than usually oppressed by the writing of this
book, thus he wrote to Sir J. D. Hooker in February:--
"You ask about my book, and all that I can say is that I am ready to
commit suicide; I thought it was decently written, but find so much
wants rewriting, that it will not be ready to go to printers for two
months, and will then make a confoundedly big book. Murray will say that
it is no use publishing in the middle of summer, so I do not know what
will be the upshot; but I begin to think that every one who publishes a
book is a fool."
The book was published on July 2nd, 1875, and 2700 copies were sold out
of the edition of 3000.
_The Kew Index of Plant-Names._
Some account of my father's connection with the _Index of Plant-Names_,
now (1892) being printed by the Clarendon Press, will be found in Mr. B.
Daydon Jackson's paper in the _Journal of Botany_, 1887, p. 151. Mr.
Jackson quotes the following statement by Sir J. D. Hooker:--
"Shortly before his death, Mr. Charles Darwin informed Sir Joseph Hooker
that it was his intention to devote a considerable sum of money annually
for some years in aid or furtherance of some work or works of practical
utility to biological science, and to make provisions in his will in the
event of these not being completed during his lifetime.
"Amongst other objects connected with botanical science, Mr. Darwin
regarded with especial interest the importance of a complete index to
the names and authors of the genera and species of plants known to
botanists, together with their native countries. Steudel's _Nomenclator_
is the only existing work of this nature, and although now nearly half a
century old, Mr. Darwin had found it of great aid in his own researches.
It has been indispensable to every botanical institution, whether as a
list of all known flowering plants, as an indication of their authors,
or as a digest of botanical geography."
Since 1840, when the _Nomenclator_ was published, the number of
described plants may be said to have doubled, so that Steudel is now
seriously below the requirements of botanical work. To remedy this want,
the _Nomenclator_ has been from time to time posted up in an interleaved
copy in the Herbarium at Kew, by the help of "funds supplied by private
liberality."[298]
My father, like other botanists, had, as Sir Joseph Hooker points out,
experienced the value of Steudel's work. He obtained plants from all
sorts of sources, which were often incorrectly named, and he felt the
necessity of adhering to the accepted nomenclature so that he might
convey to other workers precise indications as to the plants which he
had studied. It was also frequently a matter of importance to him to
know the native country of his experimental plants. Thus it was natural
that he should recognise the desirability of completing and publishing
the interleaved volume at Kew. The wish to help in this object was
heightened by the admiration he felt for the results for which the world
has to thank the Royal Gardens at Kew, and by his gratitude for the
invaluable aid which for so many years he received from its Director and
his staff. He expressly stated that it was his wish "to aid in some way
the scientific work carried on at the Royal Gardens"[299]--which induced
him to offer to supply funds for the completion of the Kew
_Nomenclator_.
The following passage, for which I am indebted to Professor Judd, is of
interest, as illustrating, the motives that actuated my father in this
matter. Professor Judd writes:--
"On the occasion of my last visit to him, he told me that his income
having recently greatly increased, while his wants remained the same, he
was most anxious to devote what he could spare to the advancement of
Geology or Biology. He dwelt in the most touching manner on the fact
that he owed so much happiness and fame to the natural history sciences,
which had been the solace of what might have been a painful
existence;--and he begged me, if I knew of any research which could be
aided by a grant of a few hundreds of pounds, to let him know, as it
would be a delight to him to feel that he was helping in promoting the
progress of science. He informed me at the same time that he was making
the same suggestion to Sir Joseph Hooker and Professor Huxley with
respect to Botany and Zoology respectively. I was much impressed by the
earnestness, and, indeed, deep emotion, with which he spoke of his
indebtedness to Science, and his desire to promote its interests."
The plan of the proposed work having been carefully considered, Sir
Joseph Hooker was able to confide its elaboration in detail to Mr. B.
Daydon Jackson, Secretary of the Linnean Society, whose extensive
knowledge of botanical literature qualifies him for the task. My
father's original idea of producing a modern edition of Steudel's
_Nomenclator_ has been practically abandoned, the aim now kept in view
is rather to construct a list of genera and species (with references)
founded on Bentham and Hooker's _Genera Plantarum_. Under Sir Joseph
Hooker's supervision, the work, carried out with admirable zeal by Mr.
Jackson, goes steadily forward. The colossal nature of the undertaking
may be estimated by the fact that the manuscript of the _Index_ is at
the present time (1892) believed to weigh more than a ton.
The Kew 'Index,' will be a fitting memorial of my father: and his share
in its completion illustrates a part of his character--his ready
sympathy with work outside his own lines of investigation--and his
respect for minute and patient labour in all branches of science.
FOOTNOTES:
[290] _Proc. Amer. Acad. of Arts and Sciences_, 1858.
[291] This view is rejected by some botanists.
[292] In the September number of _Silliman's Journal_, concluded in the
January number, 1866.
[293] _Charles Darwin_, _Nature_ Series, p. 41.
[294] Mrs. Haliburton was a daughter of my father's early friend, the
late Mr. Owen, of Woodhouse.
[295] Mrs. Haliburton had reminded him of his saying as a boy that if
Eddowes' newspaper ever alluded to him as "our deserving
fellow-townsman," his ambition would be amply gratified.
[296] _Das Bewegungsvermoegen der Pflanzen._ Vienna, 1881.
[297] The common sun-dew.
[298] _Kew Gardens Report_, 1881, p. 62.
[299] See _Nature_, January 5, 1882.