CHAPTER 2.XIII.
CLIMBING AND INSECTIVOROUS PLANTS.
[My father mentions in his 'Autobiography' (volume i.) 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." ('Proc. Amer. Acad. of Arts and
Sciences,' 1858.) 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.]
CHARLES DARWIN TO J.D. HOOKER.
Down [June] 25 [1863].
My dear Hooker,
I have been observing pretty carefully a little fact which has surprised
me; and I want to know from you and Oliver whether it seems new or odd to
you, so just tell me whenever you write; it is a very trifling fact, so do
not answer on purpose.
I have got a plant of Echinocystis lobata to observe the irritability of
the tendrils described by Asa Gray, and which of course, is plain enough.
Having the plant in my study, I have been surprised to find that the
uppermost part of each branch (i.e. the stem between the two uppermost
leaves excluding the growing tip) is CONSTANTLY and slowly twisting round
making a circle in from one-half to two hours; it will sometimes go round
two or three times, and then at the same rate untwists and twists in
opposite directions. It generally rests half an hour before it
retrogrades. The stem does not become permanently twisted. The stem
beneath the twisting portion does not move in the least, though not tied.
The movement goes on all day and all early night. It has no relation to
light for the plant stands in my window and twists from the light just as
quickly as towards it. This may be a common phenomenon for what I know,
but it confounded me quite, when I began to observe the irritability of the
tendrils. I do not say it is the final cause, but the result is pretty,
for the plant every one and a half or two hours sweeps a circle (according
to the length of the bending shoot and the length of the tendril) of from
one foot to twenty inches in diameter, and immediately that the tendril
touches any object its sensitiveness causes it immediately to seize it; a
clever gardener, my neighbour, who saw the plant on my table last night,
said: "I believe, Sir, the tendrils can see, for wherever I put a plant it
finds out any stick near enough." I believe the above is the explanation,
viz. that it sweeps slowly round and round. The tendrils have some sense,
for they do not grasp each other when young.
Yours affectionately,
C. DARWIN.
CHARLES DARWIN TO J.D. HOOKER.
Down, July 14 [1863].
My dear Hooker,
I am getting very much amused by my tendrils, it is just the sort of
niggling work which suits me, and takes up no time and rather rests me
whilst writing. So will you just think whether you know any plant, which
you could give or lend me, or I could buy, with tendrils, remarkable in any
way for development, for odd or peculiar structure, or even for an odd
place in natural arrangement. I have seen or can see Cucurbitaceae,
Passion-flower, Virginian-creeper, Cissus discolor, Common-pea and
Everlasting-pea. It is really curious the diversification of irritability
(I do not mean the spontaneous movement, about which I wrote before and
correctly, as further observation shows): for instance, I find a slight
pinch between the thumb and finger at the end of the tendril of the
Cucurbitaceae causes prompt movement, but a pinch excites no movement in
Cissus. The cause is that one side alone (the concave) is irritable in the
former; whereas both sides are irritable in Cissus, so if you excite at the
same time both OPPOSITE sides there is no movement, but by touching with a
pencil the two branches of the tendril, in any part whatever, you cause
movement towards that point; so that I can mould, by a mere touch, the two
branches into any shape I like...
CHARLES 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.
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...
CHARLES DARWIN TO ASA GRAY.
May 28, 1864.
...An Irish nobleman on his death-bed declared that he could
conscientiously say that he had never throughout life denied himself any
pleasure; and I can conscientiously say that I have never scrupled to
trouble you; so here goes.--Have you travelled South, and can you tell me
whether the trees, which Bignonia capreolata climbs, are covered with moss
or filamentous lichen or Tillandsia? (He subsequently learned from Dr.
Gray that Polypodium incanum abounds on the trees in the districts where
this species of Bignonia grows. See 'Climbing Plants,' page 103.) I ask
because its tendrils abhor a simple stick, do not much relish rough bark,
but delight in wool or moss. They adhere in a curious manner by making
little disks, like the Ampelopsis...By the way, I will enclose some
specimens, and if you think it worth while, you can put them under the
simple microscope. It is remarkable how specially adapted some tendrils
are; those of Eccremocarpus scaber do not like a stick, will have nothing
to say to wool; but give them a bundle of culms of grass, or a bundle of
bristles and they seize them well.
CHARLES DARWIN TO J.D. HOOKER.
Down, June 10 [1864].
...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. I shall be very glad of those you mention.
I have written to Veitch for young Nepenthes and Vanilla (which I believe
will turn out a grand case, though a root creeper), if I cannot buy young
Vanilla I will ask you. I have ordered a leaf-climbing fern, Lygodium.
All this work about climbers would hurt my conscience, did I think I could
do harder work. (He was much out of health at this time.)
[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:--
"For several days I have been decidedly better, and what I lay much stress
on (whatever doctors say), my brain feels far stronger, and I have lost
many dreadful sensations. 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."
On October 29, 1864, he wrote to Dr. Gray:--
"I have not been able to resist doing a little more at your godchild, my
climbing paper, or rather in size little book, which by Jove I will have
copied out, else I shall never stop. This has been new sort of work for
me, and I have been pleased to find what a capital guide for observations a
full conviction of the change of species is."
On January 19, 1865, he wrote to Sir J.D. Hooker:--
"It is working hours, but I am trying to take a day's holiday, for I
finished and despatched yesterday my climbing paper. For the last ten days
I have done nothing but correct refractory sentences, and I loathe the
whole subject."
A letter to Dr. Gray, April 9, 1865, has a word or two on the subject:--
"I have begun 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 demur to its not being necessary to explain in
detail about the spires in CAUGHT tendrils running in opposite directions;
for the fact for a long time confounded me, and I have found it difficult
enough to explain the cause to two or three persons." (August 15, 1865.)
"I received yesterday your article (In the September number of 'Silliman's
Journal,' concluded in the January number, 1866.) 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. Muller, 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."
(October 1865.)
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.]
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; 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' (volume i.), the general nature of
these early experiments. He noticed insects sticking to the leaves, and
finding that flies, etc., placed on the adhesive glands were held fast and
embraced, he suspected that the leaves were adapted to supply nitrogenous
food to the plant. 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! I
began this work on Drosera in relation to GRADATION as throwing light on
Dionaea."
Later in the autumn he was again obliged to leave home for Eastbourne,
where he continued his work on Drosera. The work was so new to him that he
found himself in difficulties in the preparation of solutions, and became
puzzled over fluid and solid ounces, etc. etc. To a friend, the late Mr.
E. Cresy, who came to his help in the matter of weights and measures, he
wrote giving an account of the experiments. The extract (November 2, 1860)
which follows illustrates the almost superstitious precautions he often
applied to his researches:--
"Generally I have scrutinised every gland and hair on the leaf before
experimenting; but it occurred to me that I might in some way affect the
leaf; though this is almost impossible, as I scrutinised with equal care
those that I put into distilled water (the same water being used for
dissolving the carbonate of ammonia). I then cut off four leaves (not
touching them with my fingers), and put them in plain water, and four other
leaves into the weak solution, and after leaving them for an hour and a
half, I examined every hair on all eight leaves; no change on the four in
water; every gland and hair affected in those in ammonia.
"I had measured the quantity of weak solution, and I counted the glands
which had absorbed the ammonia, and were plainly affected; the result
convinced me that each gland could not have absorbed more than 1/64000 or
1/65000 of a grain. I have tried numbers of other experiments all pointing
to the same result. Some experiments lead me to believe that very
sensitive leaves are acted on by much smaller doses. Reflect how little
ammonia a plant can get growing on poor soil--yet it is nourished. The
really surprising part seems to me that the effect should be visible, and
not under very high power; for after trying a high power, I thought it
would be safer not to consider any effect which was not plainly visible
under a two-thirds object glass and middle eye-piece. The effect which the
carbonate of ammonia produces is the segregation of the homogeneous fluid
in the cells into a cloud of granules and colourless fluid; and
subsequently the granules coalesce into larger masses, and for hours have
the oddest movements--coalescing, dividing, coalescing ad infinitum. I do
not know whether you will care for these ill-written details; but, as you
asked, I am sure I am bound to comply, after all the very kind and great
trouble which you have taken."
On his return home he wrote to Sir J.D. Hooker (November 21, 1860):--
"I have been working like a madman at Drosera. Here is a fact for you
which is certain as you stand where you are, though you won't believe it,
that a bit of hair 1/78000 of one grain in weight placed on gland, will
cause ONE of the gland-bearing hairs of Drosera to curve inwards, and will
alter the condition of the contents of every cell in the foot-stalk of the
gland."
And a few days later to Lyell:--
"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. The discussion in the following letter on
"nervous matter" in Drosera is of interest in relation to recent researches
on the continuity of protoplasm from cell to cell:]
CHARLES DARWIN TO J.D. HOOKER.
Cliff Cottage, Bournemouth.
September 26 [1862].
My dear Hooker,
Do not read this till you have leisure. If that blessed moment ever comes,
I should be very glad to have your opinion on the subject of this letter.
I am led to the opinion that Drosera must have diffused matter in organic
connection, closely analogous to the nervous matter of animals. When the
glands of one of the papillae or tentacles, in its natural position is
supplied with nitrogenised fluid and certain other stimulants, or when
loaded with an extremely slight weight, or when struck several times with a
needle, the pedicel bends near its base in under one minute. These varied
stimulants are conveyed down the pedicel by some means; it cannot be
vibration, for drops of fluid put on quite quietly cause the movement; it
cannot be absorption of the fluid from cell to cell, for I can see the rate
of absorption, which though quick, is far slower, and in Dionaea the
transmission is instantaneous; analogy from animals would point to
transmission through nervous matter. Reflecting on the rapid power of
absorption in the glands, the extreme sensibility of the whole organ, and
the conspicuous movement caused by varied stimulants, I have tried a number
of substances which are not caustic or corrosive,...but most of which are
known to have a remarkable action on the nervous matter of animals. You
will see the results in the enclosed paper. As the nervous matter of
different animals are differently acted on by the same poisons, one would
not expect the same action on plants and animals; only if plants have
diffused nervous matter, some degree of analogous action. And this is
partially the case. Considering these experiments, together with the
previously made remarks on the functions of the parts, I cannot avoid the
conclusion, that Drosera possesses matter at least in some degree analogous
in constitution and function to nervous matter. Now do tell me what you
think, as far as you can judge from my abstract; of course many more
experiments would have to be tried; but in former years I tried on the
whole leaf, instead of on separate glands, a number of innocuous (This line
of investigation made him wish for information on the action of poisons on
plants; as in many other cases he applied to Professor Oliver, and in
reference to the result wrote to Hooker: "Pray thank Oliver heartily for
his heap of references on poisons.") substances, such as sugar, gum,
starch, etc., and they produced no effect. Your opinion will aid me in
deciding some future year in going on with this subject. I should not have
thought it worth attempting, but I had nothing on earth to do.
My dear Hooker, Yours very sincerely,
CH. DARWIN.
P.S.--We return home on Monday 28th. Thank Heaven!
[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.]
CHARLES DARWIN 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...
[His work on digestion in Drosera and other points in the physiology of the
plant soon led him into regions where his knowledge was defective, and here
the advice and assistance which he received from Dr. Burdon Sanderson was
of much value:]
CHARLES DARWIN TO J. BURDON SANDERSON.
Down, July 25, 1873.
My dear Dr. Sanderson,
I should like to tell you a little about my recent work with Drosera, to
show that I have profited by your suggestions, and to ask a question or
two.
1. It is really beautiful how quickly and well Drosera and Dionaea
dissolve little cubes of albumen and gelatine. I kept the same sized cubes
on wet moss for comparison. When you were here I forgot that I had tried
gelatine, but albumen is far better for watching its dissolution and
absorption. Frankland has told me how to test in a rough way for pepsin;
and in the autumn he will discover what acid the digestive juice contains.
2. A decoction of cabbage-leaves and green peas causes as much inflection
as an infusion of raw meat; a decoction of grass is less powerful. Though
I hear that the chemists try to precipitate all albumen from the extract of
belladonna, I think they must fail, as the extract causes inflection,
whereas a new lot of atropine, as well as the valerianate [of atropine],
produce no effect.
3. I have been trying a good many experiments with heated water...Should
you not call the following case one of heat rigor? Two leaves were heated
to 130 deg, and had every tentacle closely inflected; one was taken out and
placed in cold water, and it re-expanded; the other was heated to 145 deg,
and had not the least power of re-expansion. Is not this latter case heat
rigor? If you can inform me, I should very much like to hear at what
temperature cold-blooded and invertebrate animals are killed.
4. I must tell you my final result, of which I am sure, [as to] the
sensitiveness of Drosera. I made a solution of one part of phosphate of
ammonia by weight to 218,750 of water; of this solution I gave so much that
a leaf got 1/8000 of a grain of the phosphate. I then counted the glands,
and each could have got only 1/1552000 of a grain; this being absorbed by
the glands, sufficed to cause the tentacles bearing these glands to bend
through an angle of 180 deg. Such sensitiveness requires hot weather, and
carefully selected young yet mature leaves. It strikes me as a wonderful
fact. I must add that I took every precaution, by trying numerous leaves
at the same time in the solution and in the same water which was used for
making the solution.
5. If you can persuade your friend to try the effects of carbonate of
ammonia on the aggregation of the white blood corpuscles, I should very
much like to hear the result.
I hope this letter will not have wearied you.
Believe me, yours very sincerely,
CHARLES DARWIN.
CHARLES DARWIN TO W. THISELTON DYER.
Down, 24 [December 1873?].
My dear Mr. Dyer,
I fear that you will think me a great bore, but I cannot resist telling you
that I have just found out that the leaves of Pinguicula possess a
beautifully adapted power of movement. Last night I put on a row of little
flies near one edge of two YOUNGISH leaves; and after 14 hours these edges
are beautifully folded over so as to clasp the flies, thus bringing the
glands into contact with the upper surfaces of the flies, and they are now
secreting copiously above and below the flies and no doubt absorbing. The
acid secretion has run down the channelled edge and has collected in the
spoon-shaped extremity, where no doubt the glands are absorbing the
delicious soup. The leaf on one side looks just like the helix of a human
ear, if you were to stuff flies within the fold. Yours most sincerely,
CH. DARWIN.
CHARLES DARWIN 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, pepsin; 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.
...I began reading the Madagascar squib (A description of a carnivorous
plant supposed to subsist on human beings.) quite gravely, and when I found
it stated that Felis and Bos inhabited Madagascar, I thought it was a false
story, and did not perceive it was a hoax till I came to the woman...
CHARLES DARWIN TO F.C. DONDERS. (Professor Donders, the well-known
physiologist of Utrecht.)
Down, July 7, 1874.
My dear Professor Donders,
My son George writes to me that he has seen you, and that you have been
very kind to him, for which I return to you my cordial thanks. He tells me
on your authority, of a fact which interests me in the highest degree, and
which I much wish to be allowed to quote. It relates to the action of one
millionth of a grain of atropine on the eye. Now will you be so kind,
whenever you can find a little leisure, to tell me whether you yourself
have observed this fact, or believe it on good authority. I also wish to
know what proportion by weight the atropine bore to the water solution, and
how much of the solution was applied to the eye. The reason why I am so
anxious on this head is that it gives some support to certain facts
repeatedly observed by me with respect to the action of phosphate of
ammonia on Drosera. The 1/4000000 of a grain absorbed by a gland clearly
makes the tentacle which bears this gland become inflected; and I am fully
convinced that 1/20000000 of a grain of the crystallised salt (i.e.
containing about one-third of its weight of water of crystallisation) does
the same. Now I am quite unhappy at the thought of having to publish such
a statement. It will be of great value to me to be able to give any
analogous facts in support. The case of Drosera is all the more
interesting as the absorption of the salt or any other stimulant applied to
the gland causes it to transmit a motor influence to the base of the
tentacle which bears the gland.
Pray forgive me for troubling you, and do not trouble yourself to answer
this until your health is fully re-established.
Pray believe me,
Yours very sincerely,
CHARLES DARWIN.
[During the summer of 1874 he was at work on the genus Utricularia, and he
wrote (July 16th) to Sir J.D. Hooker giving some account of the progress of
his work:--
"I am rather glad you have not been able to send Utricularia, for the
common species has driven F. and me almost mad. The structure is MOST
complex. The bladders catch a multitude of Entomostraca, and larvae of
insects. The mechanism for capture is excellent. But there is much that
we cannot understand. From what I have seen to-day, I strongly suspect
that it is necrophagous, i.e. that it cannot digest, but absorbs decaying
matter."
He was indebted to Lady Dorothy Nevill for specimens of the curious
Utricularia montana, which is not aquatic like the European species, but
grows among the moss and debris on the branches of trees. To this species
the following letter refers:]
CHARLES DARWIN TO LADY DOROTHY NEVILL.
Down September 18 [1874].
Dear Lady Dorothy Nevill,
I am so much obliged to you. I was so convinced that the bladders were
with the leaves that I never thought of removing the moss, and this was
very stupid of me. The great solid bladder-like swellings almost on the
surface are wonderful objects, but are not the true bladders. These I
found on the roots near the surface, and down to a depth of two inches in
the sand. They are as transparent as glass, from 1/20 to 1/100 of an inch
in size, and hollow. They have all the important points of structure of
the bladders of the floating English species, and I felt confident I should
find captured prey. And so I have to my delight in two bladders, with
clear proof that they had absorbed food from the decaying mass. For
Utricularia is a carrion-feeder, and not strictly carnivorous like Drosera.
The great solid bladder-like bodies, I believe, are reservoirs of water
like a camel's stomach. As soon as I have made a few more observations, I
mean to be so cruel as to give your plant no water, and observe whether the
great bladders shrink and contain air instead of water; I shall then also
wash all earth from all roots, and see whether there are true bladders for
capturing subterranean insects down to the very bottom of the pot. Now
shall you think me very greedy, if I say that supposing the species is not
very precious, and you have several, will you give me one more plant, and
if so, please to send it to "Orpington Station, S.E.R., to be forwarded by
foot messenger."
I have hardly ever enjoyed a day more in my life than I have this day's
work; and this I owe to your Ladyship's great kindness.
The seeds are very curious monsters; I fancy of some plant allied to
Medicago, but I will show them to Dr. Hooker.
Your ladyship's very gratefully,
CH. DARWIN.
CHARLES DARWIN TO J.D. HOOKER.
Down, September 30, 1874.
My dear H.,
Your magnificent present of Aldrovanda has arrived quite safe. I have
enjoyed greatly a good look at the shut leaves, one of which I cut open.
It is an aquatic Dionaea, which has acquired some structures identical with
those of Utricularia!
If the leaves open and I can transfer them open under the microscope, I
will try some experiments, for mortal man cannot resist the temptation. If
I cannot transfer, I will do nothing, for otherwise it would require
hundreds of leaves.
You are a good man to give me such pleasure.
Yours affectionately,
C. DARWIN.
[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.]
