603. TO J.D. HOOKER. Down, October 22nd. [1861]…

603. TO J.D. HOOKER. Down, October 22nd. [1861]

Acropera is a beast,--stigma does not open, everything seems contrived that it shall NOT be anyhow fertilised. There is something very odd about it, which could only be made out by incessant watching on several individual plants.

I never saw the very curious flower of Canna; I should say the pollen was deposited where it is to prevent inevitable self-fertilisation. You have no time to try the smallest experiment, else it would be worth while to put pollen on some stigmas (supposing that it does not seed freely with you). Anyhow, insects would probably carry pollen from flower to flower, for Kurr states the tube formed by pistil, stamen and "nectarblatt" secretes (I presume internally) much nectar. Thanks for sending me the curious flower.

Now I want much some wisdom; though I must write at considerable length, your answer may be very brief.

(FIGURE 8.--FLORAL DIAGRAM OF AN ORCHID. The "missing bundle" could not be found in some species.)

In R. Brown's admirable paper in the "Linnean Transacts." (603/4. Volume XVI., page 685.) he suggests (and Lindley cautiously agrees) that the flower of orchids consists of five whorls, the inner whorl of the two whorls of anthers being all rudimentary, and when the labellum presents ridges, two or three of the anthers of both whorls [are] combined with it. In the ovarium there are six bundles of vessels: R. Brown judged by transverse sections. It occurred to me, after what you said, to trace the vessels longitudinally, and I have succeeded well. Look at my diagram [Figure 8] (which please return, for I am transported with admiration at it), which shows the vessels which I have traced, one bundle to each of fifteen theoretical organs, and no more. You will see the result is nothing new, but it seems to confirm strongly R. Brown, for I have succeeded (perhaps he did, but he does not say so) in tracing the vessels belonging to each organ in front of each other to the same bundle in the ovarium: thus the vessels going to the lower sepal, to the side of the labellum, and to one stigma (when there are two) all distinctly branch from one ovarian bundle. So in other cases, but I have not completely traced (only seen) that going to the rostellum. But here comes my only point of novelty: in all orchids as yet looked at (even one with so simple a labellum as Gymnadenia and Malaxis) the vessels on the two sides of the labellum are derived from the bundle which goes to the lower sepal, as in the diagram. This leads me to conclude that the labellum is always a compound organ. Now I want to know whether it is conceivable that the vessels coming from one main bundle should penetrate an organ (the labellum) which receives its vessels from another main bundle? Does it not imply that all that part of the labellum which is supplied by vessels coming from a lateral bundle must be part of a primordially distinct organ, however closely the two may have become united? It is curious in Gymnadenia to trace the middle anterior bundle in the ovarium: when it comes to the orifice of the nectary it turns and runs right down it, then comes up the opposite side and runs to the apex of the labellum, whence each side of the nectary is supplied by vessels from the bundles, coming from the lower sepals. Hence even the thin nectary is essentially, I infer, tripartite; hence its tendency to bifurcation at its top. This view of the labellum always consisting of three organs (I believe four when thick, as in Mormodes, at base) seems to me to explain its great size and tripartite form, compared with the other petals. Certainly, if I may trust the vessels, the simple labellum of Gymnadenia consists of three organs soldered together. Forgive me for writing at such length; a very brief answer will suffice. I am desperately interested in the subject: the destiny of the whole human race is as nothing to the course of vessels of orchids...

What plant has the most complex single stigma and pistil? The most complex I, in my ignorance, can think of is in Iris. I want to know whether anything beats in modification the rostellum of Catasetum. To-morrow I mean to be at Catasetum. Hurrah! What species is it? It is wonderfully different from that which Veitch sent me, which was C. saccatum.

According to the vessels, an orchid flower consists of three sepals and two petals free; and of a compound organ (its labellum), consisting of one petal and of two (or three) modified anthers; and of a second compound body consisting of three pistils, one normal anther, and two modified anthers often forming the sides of the clinandrum.

604. TO JOHN LINDLEY

(604/1. It was in the autumn of 1861 that Darwin made up his mind to publish his Orchid work as a book, rather than as a paper in the Linnean Society's "Journal." (604/2. See "Life and Letters," III., page 266.) The following letter shows that the new arrangement served as an incitement to fresh work.)

Down, October 25th [1861?]

Mr. James Veitch has been most generous. I did not know that you had spoken to him. If you see him pray say I am truly grateful; I dare not write to a live Bishop or a Lady, but if I knew the address of "Rucker"? and might use your name as introduction, I might write. I am half mad on the subject. Hooker has sent me many exotics, but I stopped him, for I thought I should make a fool of myself; but since I have determined to publish I much regret it.

(FIGURE 9.--HABENARIA CHLORANTHA (Longitudinal course of bundles).)

(605/1. The three upper curved outlines, two of which passing through the words "upper sepal," "upper petal," "lower sepal," were in red in the original; for explanation see text.)

605. TO J.D. HOOKER

(605/2. The following letter is of interest because it relates to one of the two chief difficulties Darwin met with in working out the morphology of the orchid flower. In the orchid book (605/3. Edition I., page 303.) he wrote, "This anomaly [in Habenaria] is so far of importance, as it throws some doubt on the view which I have taken of the labellum being always an organ compounded of one petal and two petaloid stamens." That is to say, it leaves it open for a critic to assert that the vessels which enter the sides of the labellum are lateral vessels of the petal and do not necessarily represent petaloid stamens. In the sequel he gives a satisfactory answer to the supposed objector.)

Down, November 10th, [1861].

For the love of God help me. I believe all my work (about a fortnight) is useless. Look at this accursed diagram (Figure 9) of the butterfly-orchis [Habenaria], which I examined after writing to you yesterday, when I thought all my work done. Some of the ducts of the upper sepal (605/4. These would be described by modern morphologists as lower, not upper, sepals, etc. Darwin was aware that he used these terms incorrectly.) and upper petal run to the wrong bundles on the column. I have seen no such case.

This case apparently shows that not the least reliance can be placed on the course of ducts. I am sure of my facts.

There is great adhesion and extreme displacement of parts where the organs spring from the top of the ovarium. Asa Gray says ducts are very early developed, and it seems to me wonderful that they should pursue this course. It may be said that the lateral ducts in the labellum running into the antero-lateral ovarian bundle is no argument that the labellum consists of three organs blended together.

In desperation (and from the curious way the base of upper petals are soldered at basal edges) I fancied the real form of upper sepal, upper petal and lower sepal might be as represented by red lines, and that there had been an incredible amount of splitting of sepals and petals and subsequent fusion.

This seems a monstrous notion, but I have just looked at Bauer's drawing of allied Bonatea, and there is a degree of lobing of petals and sepals which would account for anything.

Now could you spare me a dry flower out of your Herbarium of Bonatea speciosa (605/5. See "Fertilisation of Orchids," Edition I., page 304 (note), where the resemblances between the anomalous vessels of Bonatea and Habenaria are described. On November 14th, 1861, he wrote to Sir Joseph: "You are a true friend in need. I can hardly bear to let the Bonatea soak long enough."), that I might soak and look for ducts. If I cannot explain the case of Habenaria all my work is smashed. I was a fool ever to touch orchids.

606. TO J.D. HOOKER. Down, November 17th [1861]

What two very interesting and useful letters you have sent me. You rather astound me with respect to value of grounds of generalisation in the morphology of plants. It reminds me that years ago I sent you a grass to name, and your answer was, "It is certainly Festuca (so-and-so), but it agrees as badly with the description as most plants do." I have often laughed over this answer of a great botanist...Lindley, from whom I asked for an orchid with a simple labellum, has most kindly sent me a lot of what he marks "rare" and "rarissima" of peloric orchids, etc., but as they are dried I know not whether they will be of use. He has been most kind, and has suggested my writing to Lady D. Nevill, who has responded in a wonderfully kind manner, and has sent a lot of treasures. But I must stop; otherwise, by Jove, I shall be transformed into a botanist. I wish I had been one; this morphology is surprisingly interesting. Looking to your note, I may add that certainly the fifteen alternating bundles of spiral vessels (mingled with odd beadlike vessels in some cases) are present in many orchids. The inner whorl of anther ducts are oftenest aborted. I must keep clear of Apostasia, though I have cast many a longing look at it in Bauer. (606/1. Apostasia has two fertile anthers like Cypripedium. It is placed by Engler and Prantl in the Apostasieae or Apostasiinae, among the Orchideae, by others in a distinct but closely allied group.)

I hope I may be well enough to read my own paper on Thursday, but I have been very seedy lately. (606/2. "On the two Forms, or Dimorphic Condition, in the Species of the Genus Primula," "Linn. Soc. Journ." 1862. He did read the paper, but it cost him the next day in bed. "Life and Letters," III., page 299.) I see there is a paper at the Royal on the same night, which will more concern you, on fossil plants of Bovey (606/3. Oswald Heer, "The Fossil Flora of Bovey Tracey," "Phil. Trans. R. Soc." 1862, page 1039.), so that I suppose I shall not have you; but you must read my paper when published, as I shall very much like to hear what you think. It seems to me a large field for experiment. I shall make use of my Orchid little volume in illustrating modification of species doctrine, but I keep very, very doubtful whether I am not doing a foolish action in publishing. How I wish you would keep to your old intention and write a book on plants. (606/4. Possibly a book similar to that described in Letter 696.)

607. TO G. BENTHAM. Down, November 26th [1861]

Our notes have crossed on the road. I know it is an honour to have a paper in the "Transactions," and I am much obliged to you for proposing it, but I should greatly prefer to publish in the "Journal." Nor does this apply exclusively to myself, for in old days at the Geological Society I always protested against an abstract appearing when the paper itself might appear. I abominate also the waste of time (and it would take me a day) in making an abstract. If the referee on my paper should recommend it to appear in the "Transactions," will you be so kind as to lay my earnest request before the Council that it may be permitted to appear in the "Journal?"

You must be very busy with your change of residence; but when you are settled and have some leisure, perhaps you will be so kind as to give me some cases of dimorphism, like that of Primula. Should you object to my adding them to those given me by A. Gray? By the way, I heard from A. Gray this morning, and he gives me two very curious cases in Boragineae.

608. TO JOHN LINDLEY

(608/1. In the following fragment occurs the earliest mention of Darwin's work on the three sexual forms of Catasetum tridentatum. Sir R. Schomburgk (608/2. "Trans. Linn. Soc." XVII., page 522.) described Catasetum tridentatum, Monacanthus viridis and Myanthus barbatus occurring on a single plant, but it remained for Darwin to make out that they are the male, female and hermaphrodite forms of a single species. (608/3. "Fertilisation of Orchids," Edition I., page 236; Edition II., page 196.)

With regard to the species of Acropera (Gongora) (608/4. Acropera Loddigesii = Gongora galeata: A. luteola = G. fusca ("Index Kewensis").) he was wrong in his surmise. The apparent sterility seems to be explicable by Hildebrand's discovery (608/5. "Bot. Zeitung," 1863 and 1865.) that in some orchids the ovules are not developed until pollinisation has occurred. (608/6. "Fertilisation of Orchids," Edition II., page 172. See Letter 633.))

Down, December 15th [1861].

I am so nearly ready for press that I will not ask for anything more; unless, indeed, you stumbled on Mormodes in flower. As I am writing I will just mention that I am convinced from the rudimentary state of the ovules, and from the state of the stigma, that the whole plant of Acropera luteola (and I believe A. Loddigesii) is male. Have you ever seen any form from the same countries which could be the females? Of course no answer is expected unless you have ever observed anything to bear on this. I may add [judging from the] state of the ovules and of the pollen [that]:--

Catasetum tridentatum is male (and never seeds, according to Schomburgk, whom you have accidentally misquoted in the "Vegetable Kingdom"). Monacanthus viridis is female. Myanthus barbatus is the hermaphrodite form of same species.

609. TO J.D. HOOKER. Down, December 18th [1861]

Thanks for your note. I have not written for a long time, for I always fancy, busy as you are, that my letters must be a bore; though I like writing, and always enjoy your notes. I can sympathise with you about fear of scarlet fever: to the day of my death I shall never forget all the sickening fear about the other children, after our poor little baby died of it. The "Genera Plantarum" must be a tremendous work, and no doubt very valuable (such a book, odd as it may appear, would be very useful even to me), but I cannot help being rather sorry at the length of time it must take, because I cannot enter on and understand your work. Will you not be puzzled when you come to the orchids? It seems to me orchids alone would be work for a man's lifetime; I cannot somehow feel satisfied with Lindley's classification; the Malaxeae and Epidendreae seem to me very artificially separated. (609/1. Pfitzer (in the "Pflanzenfamilien") places Epidendrum in the Laeliinae-Cattleyeae, Malaxis in the Liparidinae. He states that Bentham united the Malaxideae and Epidendreae.) Not that I have seen enough to form an opinion worth anything.

Your African plant seems to be a vegetable Ornithorhynchus, and indeed much more than that. (609/2. See Sir J.D. Hooker, "On Welwitschia, a new genus of Gnetaceae." "Linn. Soc. Trans." XXIV., 1862-3.) The more I read about plants the more I get to feel that all phanerogams seem comparable with one class, as lepidoptera, rather than with one kingdom, as the whole insecta. (609/3. He wrote to Hooker (December 28th, 1861): "I wrote carelessly about the value of phanerogams; what I was thinking of was that the sub-groups seemed to blend so much more one into another than with most classes of animals. I suspect crustacea would show more difference in the extreme forms than phanerogams, but, as you say, it is wild speculation. Yet it is very strange what difficulty botanists seem to find in grouping the families together into masses.")

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.

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.

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.

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.

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.

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.)

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.)

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.

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.)

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.

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.)

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.

P.S.--Do you happen to know, when there are only four stamens, whether it is the petal or sepal-facers which are preserved? and whether in the four-stamened forms the pistil is rectangularly bent or is straight?

621. TO ASA GRAY. Down, February 16th [1862?]

I have been trying a few experiments on Melastomads; and they seem to indicate that the pollen of the two curious sets of anthers (i.e. the petal-facers and the sepal-facers) have very different powers; and it does not seem that the difference is connected with any tendency to abortion in the one set. Now I think I can understand the structure of the flower and means of fertilisation, if there be two forms,--one with the pistil bent rectangularly out of the flower, and the other with it nearly straight.

Our hot-house and green-house plants have probably all descended by cuttings from a single plant of each species; so I can make out nothing from them. I applied in vain to Bentham and Hooker; but Oliver picked out some sentences from Naudin, which seem to indicate differences in the position of the pistil.

I see that Rhexia grows in Massachusetts; and I suppose has two different sets of stamens. Now, if in your power, would you observe the position of the pistil in different plants, in lately opened flowers of the same age? (I specify this because in Monochaetum I find great changes of position in the pistils and stamens, as flower gets old). Supposing that my prophecy should turn out right, please observe whether in both forms the passage into the flower is not [on] the upper side of the pistil, owing to the basal part of the pistil lying close to the ring of filaments on the under side of the flower. Also I should like to know the colour of the two sets of anthers. This would take you only a few minutes, and is the only way I see that I can find out whether these plants are dimorphic in this peculiar way--i.e., only in the position of the pistil (621/1. In Exacum and in Saintpaulia the flowers are dimorphic in this sense: the style projects to either the right or the left side of the corolla, from which it follows that a right-handed flower would fertilise a left-handed one, and vice versa. See Willis, "Flowering Plants and Ferns," 1897, Volume I., page 73.) and in its relation to the two kinds of pollen. I am anxious about this, because if it should prove so, it will show that all plants with longer and shorter or otherwise different anthers will have to be examined for dimorphism.

622. TO ASA GRAY. March 15th [1862]

...I wrote some little time ago about Rhexia; since then I have been carefully watching and experimenting on another genus, Monochaetum; and I find that the pistil is first bent rectangularly (as in the sketch sent), and then in a few days becomes straight: the stamens also move. If there be not two forms of Rhexia, will you compare the position of the part in young and old flowers? I have a suspicion (perhaps it will be proved wrong when the seed-capsules are ripe) that one set of anthers are adapted to the pistil in early state, and the other set for it in its later state. If bees visit the Rhexia, for Heaven's sake watch exactly how the anther and stigma strike them, both in old and young flowers, and give me a sketch.

Again I say, do not hate me.

623. TO J.D. HOOKER. Leith Hill Place, Dorking, Thursday, 15th [May 1862]

You stated at the Linnean Society that different sets of seedling Cinchona (623/1. Cinchona is apparently heterostyled: see "Forms of Flowers," Edition II., page 134.) grew at very different rate, and from my Primula case you attributed it probably to two sorts of pollen. I confess I thought you rash, but I now believe you were quite right. I find the yellow and crimson anthers of the same flower in the Melastomatous Heterocentron roseum have different powers; the yellow producing on the same plant thrice as many seeds as the crimson anthers. I got my neighbour's most skilful gardener to sow both kinds of seeds, and yesterday he came to me and said it is a most extraordinary thing that though both lots have been treated exactly alike, one lot all remain dwarfs and the other lot are all rising high up. The dwarfs were produced by the pollen of the crimson anthers. In Monochaetum ensiferum the facts are more complex and still more strange; as the age and position of the pistils comes into play, in relation to the two kinds of pollen. These facts seem to me so curious that I do not scruple to ask you to see whether you can lend me any Melastomad just before flowering, with a not very small flower, and which will endure for a short time a greenhouse or sitting-room; when fertilised and watered I could send it to Mr. Turnbull's to a cool stove to mature seed. I fully believe the case is worth investigation.

P.S.--You will not have time at present to read my orchid book; I never before felt half so doubtful about anything which I published. When you read it, do not fear "punishing" me if I deserve it.

Adios. I am come here to rest, which I much want.

Whenever you have occasion to write, pray tell me whether you have Rhododendron Boothii from Bhootan, with a smallish yellow flower, and pistil bent the wrong way; if so, I would ask Oliver to look for nectary, for it is an abominable error of Nature that must be corrected. I could hardly believe my eyes when I saw the pistil.

624. TO ASA GRAY. January 19th [1863]

I have been at those confounded Melastomads again; throwing good money (i.e. time) after bad. Do you remember telling me you could see no nectar in your Rhexia? well, I can find none in Monochaetum, and Bates tells me that the flowers are in the most marked manner neglected by bees and lepidoptera in Amazonia. Now the curious projections or horns to the stamens of Monochaetum are full of fluid, and the suspicion occurs to me that diptera or small hymenoptera may puncture these horns like they puncture (proved since my orchid book was published) the dry nectaries of true Orchis. I forget whether Rhexia is common; but I very much wish you would next summer watch on a warm day a group of flowers, and see whether they are visited by small insects, and what they do.

625. TO I.A. HENRY. Down, January 20th [1863]

...You must kindly permit me to mention any point on which I want information. If you are so inclined, I am curious to know from systematic experiments whether Mr. D. Beaton's statement that the pollen of two shortest anthers of scarlet Pelargonium produce dwarf plants (625/1. See "Animals and Plants," Edition II., Volume II., page 150, for a brief account of Darwin's experiments on this genus. Also loc. cit., page 338 (note), for a suggested experiment.), in comparison with plants produced from the same mother-plant by the pollen of longer stamens from the same flower. It would aid me much in some laborious experiments on Melastomads. I confess I feel a little doubtful; at least, I feel pretty nearly sure that I know the meaning of short stamens in most plants. This summer (for another object) I crossed Queen of Scarlet Pelargonium with pollen of long and short stamens of multiflora alba, and it so turns out that plants from short stamens are the tallest; but I believe this to have been mere chance. My few crosses in Pelargonium were made to get seed from the central peloric or regular flower (I have got one from peloric flower by pollen of peloric), and this leads me to suggest that it would be very interesting to test fertility of peloric flowers in three ways,--own peloric pollen on peloric stigma, common pollen on peloric stigma, peloric pollen on common stigma of same species. My object is to discover whether with change of structure of flower there is any change in fertility of pollen or of female organs. This might also be tested by trying peloric and common pollen on stigma of a distinct species, and conversely. I believe there is a peloric and common variety of Tropaeolum, and a peloric or upright and common variation of some species of Gloxinia, and the medial peloric flowers of Pelargonium, and probably others unknown to me.

626. TO I.A. HENRY. Hartfield, May 2nd [1863]

In scarlet dwarf Pelargonium, you will find occasionally an additional and abnormal stamen on opposite and lower side of flower. Now the pollen of this one occasional short stamen, I think, very likely would produce dwarf plants. If you experiment on Pelargonium I would suggest your looking out for this single stamen.

I observed fluctuations in length of pistil in Phloxes, but thought it was mere variability.

If you could raise a bed of seedling Phloxes of any species except P. Drummondii, it would be highly desirable to see if two forms are presented, and I should be very grateful for information and flowers for inspection. I cannot remember, but I know that I had some reason to look after Phloxes. (626/1. See "Forms of Flowers," Edition II., page 119, where the conjecture is hazarded that Phlox subulata shows traces of a former heterostyled condition.)

I do not know whether you have used microscopes much yet. It adds immensely to interest of all such work as ours, and is indeed indispensable for much work. Experience, however, has fully convinced me that the use of the compound without the simple microscope is absolutely injurious to progress of N[atural] History (excepting, of course, with Infusoria). I have, as yet, found no exception to the rule, that when a man has told me he works with the compound alone his work is valueless.

627. TO ASA GRAY. March 20th [1863]

I wrote to him [Dr. H. Cruger, of Trinidad] to ask him to observe what the insects did in the flowers of Melastomaceae: he says not proper season yet, but that on one species a small bee seemed busy about the horn-like appendages to the anthers. It will be too good luck if my study of the flowers in the greenhouse has led me to right interpretation of these appendages.

628. TO J.D. HOOKER. Down, November 28th [1871]

If you had come here on Sunday I should have asked you whether you could give me seed or seedlings of any Melastomad which would flower soon to experiment on! I wrote also to J. Scott to ask if he could give me seed.

Several years ago I raised a lot of seedlings of a Melastomad greenhouse bush (Monochaetus or some such name) (628/1. Monochaetum.) from stigmas fertilised separately by the two kinds of pollen, and the seedlings differed remarkably in size, and whilst young, in appearance; and I never knew what to think of the case (so you must not use it), and have always wished to try again, but they are troublesome beasts to fertilise.

On the other hand I could detect no difference in the product from the two coloured anthers of Clarkia. (628/2. Clarkia has eight stamens divided into two groups which differ in the colour of the anthers.) If you want to know further particulars of my experiments on Monochaetum (?) and Clarkia, I will hunt for my notes. You ask about difference in pollen in the same species. All dimorphic and trimorphic plants present such difference in function and in size. Lythrum and the trimorphic Oxalis are the most wonderful cases. The pollen of the closed imperfect cleistogamic flowers differ in the transparency of the integument, and I think in size. The latter point I could ascertain from my notes. The pollen or female organs must differ in almost every individual in some manner; otherwise the pollen of varieties and even distinct individuals of same varieties would not be so prepotent over the individual plant's own pollen. Here follows a case of individual differences in function of pollen or ovules or both. Some few individuals of Reseda odorata and R. lutea cannot be fertilised, or only very rarely, by pollen of the same plant, but can by pollen of any other individual. I chanced to have two plants of R. odorata in this state; so I crossed them and raised five seedlings, all of which were self sterile and all perfectly fertile with pollen of any other individual mignonette. So I made a self sterile race! I do not know whether these are the kinds of facts which you require.

Think whether you can help me to seed or better seedlings (not cuttings) of any Melastomad.

629. TO F. MULLER. Down, March 20th, 1881

I have received the seeds and your most interesting letter of February 7th. The seeds shall be sown, and I shall like to see the plants sleeping; but I doubt whether I shall make any more detailed observations on this subject, as, now that I feel very old, I require the stimulus of some novelty to make me work. This stimulus you have amply given me in your remarkable view of the meaning of the two-coloured stamens in many flowers. I was so much struck with this fact with Lythrum, that I began experimenting on some Melastomaceae, which have two sets of extremely differently coloured anthers. After reading your letter I turned to my notes (made 20 years ago!) to see whether they would support or contradict your suggestion. I cannot tell yet, but I have come across one very remarkable result, that seedlings from the crimson anthers were not 11/20ths of the size of seedlings from the yellow anthers of the same flowers. Fewer good seeds were produced by the crimson pollen. I concluded that the shorter stamens were aborting, and that the pollen was not good. (629/1. "Shorter stamens" seems to be a slip of the pen for "longer,"--unless the observations were made on some genus in which the structure is unusual.) The mature pollen is incoherent, and must be [word illegible] against the visiting insect's body. I remembered this, and I find it said in my EARLY notes that bees would never visit the flowers for pollen. This made me afterwards write to the late Dr. Cruger in the West Indies, and he observed for me the flowers, and saw bees pressing the anthers with their mandibles from the base upwards, and this forced a worm-like thread of pollen from the terminal pore, and this pollen the bees collected with their hind legs. So that the Melastomads are not opposed to your views.

I am now working on the habits of worms, and it tires me much to change my subject; so I will lay on one side your letter and my notes, until I have a week's leisure, and will then see whether my facts bear on your views. I will then send a letter to "Nature" or to the Linn. Soc., with the extract of your letter (and this ought to appear in any case), with my own observations, if they appear worth publishing. The subject had gone out of my mind, but I now remember thinking that the imperfect action of the crimson stamens might throw light on hybridism. If this pollen is developed, according to your view, for the sake of attracting insects, it might act imperfectly, as well as if the stamens were becoming rudimentary. (629/2. As far as it is possible to understand the earlier letters it seems that the pollen of the shorter stamens, which are adapted for attracting insects, is the most effective.) I do not know whether I have made myself intelligible.

630. TO W. THISELTON-DYER. Down, March 21st [1881]

I have had a letter from Fritz Muller suggesting a novel and very curious explanation of certain plants producing two sets of anthers of different colour. This has set me on fire to renew the laborious experiments which I made on this subject, now 20 years ago. Now, will you be so kind as to turn in your much worked and much holding head, whether you can think of any plants, especially annuals, producing 2 such sets of anthers. I believe that this is the case with Clarkia elegans, and I have just written to Thompson for seeds. The Lythraceae must be excluded, as these are heterostyled.

I have got seeds from Dr. King of some Melastomaceae, and will write to Veitch to see if I can get the Melastomaceous genera Monochaetum and Heterocentron or some such name, on which I before experimented. Now, if you can aid me, I know that you will; but if you cannot, do not write and trouble yourself.

2.X.III. CORRESPONDENCE WITH JOHN SCOTT, 1862-1871.

"If he had leisure he would make a wonderful observer, to my judgment; I have come across no one like him."--Letter to J.D. Hooker, May 29th [1863].

(631/1. The following group of letters to John Scott, of whom some account is given elsewhere (Volume I., Letters 150 and 151, and Index.) deal chiefly with experimental work in the fertilisation of flowers. In addition to their scientific importance, several of the letters are of special interest as illustrating the encouragement and friendly assistance which Darwin gave to his correspondent.)

631. JOHN SCOTT TO CHARLES DARWIN. Edinburgh Botanic Gardens, November 11th, 1862

I take the liberty of addressing you for the purpose of directing your attention to an error in one of your ingenious explanations of the structural adaptations of the Orchidaceae in your late work. This occurs in the genus Acropera, two species of which you assume to be unisexual, and so far as known represented by male individuals only. Theoretically you have no doubt assigned good grounds for this view; nevertheless, experimental observations that I am now making have already convinced me of its fallacy. And I thus hurriedly, and as you may think prematurely, direct your attention to it, before I have seen the final result of my own experiment, that you might have the longer time for reconsidering the structure of this genus for another edition of your interesting book, if indeed it be not already called for. I am furthermore induced to communicate the results of my yet imperfect experiments in the belief that the actuating principle of your late work is the elicitation of truth, and that you will gladly avail yourself of this even at the sacrifice of much ingenious theoretical argumentation.

Since I have had an opportunity of perusing your work on orchid fertilisation, my attention has been particularly directed to the curiously constructed floral organs of Acropera. I unfortunately have as yet had only a few flowers for experimental enquiry, otherwise my remarks might have been clearer and more satisfactory. Such as they are, however, I respectfully lay [them] before you, with a full assurance of their veracity, and I sincerely trust that as such you will receive them.

Your observations seem to have been chiefly directed to the A. luteola, mine to the A. Loddigesii, which, however, as you remark, is in a very similar constructural condition with the former; having the same narrow stigmatic chamber, abnormally developed placenta, etc. In regard to the former point--contraction of stigmatic chamber--I may remark that it does not appear to be absolutely necessary that the pollen-masses penetrate this chamber for effecting fecundation. Thus a raceme was produced upon a plant of A. Loddigesii in the Botanic Gardens here lately; upon this I left only six flowers. These I attempted to fertilise, but with two only of the six have I been successful: I succeeded in forcing a single pollen-mass into the stigmatic chamber of one of the latter, but I failed to do this on the other; however, by inserting a portion of a pedicel with a pollinium attached, I caused the latter to adhere, with a gentle press, to the mouth of the stigmatic chamber. Both of these, as I have already remarked, are nevertheless fertilised; one of them I have cut off for examination, and its condition I will presently describe; the other is still upon the plant, and promises fair to attain maturity. In regard to the other four flowers, I may remark that though similarly fertilised--part having pollinia inserted, others merely attached--they all withered and dropped off without the least swelling of the ovary. Can it be, then, that this is really an [andro-monoecious] species?--part of the flowers male, others truly hermaphrodite.

In making longitudinal sections of the fertilised ovary before mentioned, I found the basal portion entirely destitute of ovules, their place being substituted by transparent cellular ramification of the placentae. As I traced the placentae upwards, the ovules appeared, becoming gradually more abundant towards its apex. A transverse section near the apex of the ovary, however, still exhibited a more than ordinary placental development--i.e. [congenitally?] considered--each end giving off two branches, which meet each other in the centre of the ovary, the ovules being irregularly and sparingly disposed upon their surfaces.

In regard to the mere question of fertilisation, then, I am perfectly satisfied, but there are other points which require further elucidation. Among these I may particularly refer to the contracted stigmatic chamber, and the slight viscidity of its disk. The latter, however, may be a consequence of uncongenial conditions--as you do not mention particularly its examination by any author in its natural habitat. If such be the case, the contracted stigmatic chamber will offer no real difficulty, should the viscous exudations be only sufficient to render the mouth adhesive. For, as I have already shown, the pollen-tubes may be emitted in this condition, and effect fecundation without being in actual contact with the stigmatic surface, as occurs pretty regularly in the fertilisation of the Stapelias, for example. But, indeed, your own discovery of the independent germinative capabilities of the pollen-grains of certain Orchidaceae is sufficiently illustrative of this.

I may also refer to the peculiar abnormal condition that many at least of the ovaries present in a comparative examination of the placentae, and of which I beg to suggest the following explanation, though it is as yet founded on limited observations. In examining certain young ovaries of A. Loddigesii, I found some of them filled with the transparent membranous fringes of more or less distinctly cellular matter, which, from your description of the ovaries of luteola, appears to differ simply in the greater development in the former species. Again, in others I found small mammillary bodies, which appeared to be true ovules, though I could not perfectly satisfy myself as to the existence of the micropyle or nucleus. I unfortunately neglected to apply any chemical test. The fact, however, that in certain of the examined ovaries few or none of the latter bodies occurred--the placenta alone being developed in an irregular membranous form, taken in conjunction with the results of my experiments--before alluded to--on their fertilisation, leads me to infer that two sexual conditions are presented by the flowers of this plant. In short, that many of the ovaries are now normally abortive, though Nature occasionally makes futile efforts for their perfect development, in the production of ovuloid bodies; these then I regard as the male flowers. The others that are still capable of fertilisation, and likewise possessing male organs, are hermaphrodite, and must, I think, from the results of your comparative examinations, present a somewhat different condition; as it can scarcely be supposed that ovules in the condition you describe could ever be fertilised.

This is at least the most plausible explanation I can offer for the different results in my experiments on the fertilisation of apparently similar morphologically constructed flowers; others may, however, occur to you. Here there is not, as in the Catasetum, any external change visible in the respective unisexual and bisexual flowers. And yet it would appear from your researches that the ovules of Acropera are in a more highly atrophied condition than occurs in Catasetum, though, as you likewise remark, M. Neumann has never succeeded in fertilising C. tridentatum. If there be not, then, an arrangement of the reproductive structures, such as I have indicated, how can the different results in M. Neumann's experiments and mine be accounted for? However, as you have examined many flowers of both A. luteola and Loddigesii, such a difference in the ovulary or placental structures could scarcely have escaped your observation. But, be this as it may, the--to me at least--demonstrated fact still remains, that certain flowers of A. Loddigesii are capable of fertilisation, and that, though there are good grounds for supposing that important physiological changes are going on in the sexual phenomena of this species, there is no evidence whatever for supposing that external morphological changes have so masked certain individuals as to prevent their recognition.

I would now, sir, in conclusion beg you to excuse me for this infringement upon your valuable time, as I have been induced to write you in the belief that you have had negative results from other experimenters, before you ventured to propose your theoretical explanation, and consequently that you have been unknowingly led into error. I will continue, as opportunities present themselves, to examine the many peculiarities you have pointed out in this as well as others of the Orchid family; and at present I am looking forward with anxiety for the maturation of the ovary of A. Loddigesii, which will bear testimony to the veracity of the remarks I have ventured to lay before you.

632. TO J.D. HOOKER. Down, 18th [November 1862]

Strange to say, I have only one little bother for you to-day, and that is to let me know about what month flowers appear in Acropera Loddigesii and luteola; for I want extremely to beg a few more flowers, and if I knew the time I would keep a memorandum to remind you. Why I want these flowers is (and I am much alarmed) that Mr. J. Scott, of Bot. Garden of Edinburgh (do you know anything of him?) has written me a very long and clever letter, in which he confirms most of my observations; but tells me that with much difficulty he managed to get pollen into orifice, or as far as mouth of orifice, of six flowers of A. Loddigesii (the ovarium of which I did not examine), and two pods set; one he gathered, and saw a very few ovules, as he thinks, on the large and mostly rudimentary placenta. I shall be most curious to hear whether the other pod produces a good lot of seed. He says he regrets that he did not test the ovules with chemical agents: does he mean tincture of iodine? He suggests that in a state of nature the viscid matter may come to the very surface of stigmatic chamber, and so pollen-masses need not be inserted. This is possible, but I should think improbable. Altogether the case is very odd, and I am very uneasy, for I cannot hope that A. Loddigesii is hermaphrodite and A. luteola the male of the same species. Whenever I can get Acropera would be a very good time for me to look at Vanda in spirits, which you so kindly preserved for me.

633. TO J. SCOTT

(633/1. The following is Darwin's reply to the above letter from Scott. In the first edition of "Fertilisation of Orchids" (page 209) he assumed that the sexes in Acropera, as in Catasetum, were separate. In the second edition (page 172) he writes: "I was, however, soon convinced of my error by Mr. Scott, who succeeded in artificially fertilising the flowers with their own pollen. A remarkable discovery by Hildebrand (633/2. "Bot. Zeitung," 1863 and 1865.), namely, that in many orchids the ovules are not developed unless the stigma is penetrated by the pollen-tubes...explains the state of the ovarium in Acropera, as observed by me." In regard to this subject see Letter 608.)

Down, November 12th, 1862.

I thank you most sincerely for your kindness in writing to me, and for [your] very interesting letter. Your fact has surprised me greatly, and has alarmed me not a little, for if I am in error about Acropera I may be in error about Catasetum. Yet when I call to mind the state of the placentae in A. luteola, I am astonished that they should produce ovules. You will see in my book that I state that I did not look at the ovarium of A. Loddigesii. Would you have the kindness to send me word which end of the ovarium is meant by apex (that nearest the flower?), for I must try and get this species from Kew and look at its ovarium. I shall be extremely curious to hear whether the fruit, which is now maturing, produces a large number of good and plump seed; perhaps you may have seen the ripe capsules of other Vandeae, and may be able to form some conjecture what it ought to produce. In the young, unfertilised ovaria of many Vandeae there seemed an infinitude of ovules. In desperation it occurs to me as just possible, as almost everything in nature goes by gradation, that a properly male flower might occasionally produce a few seeds, in the same manner as female plants sometimes produce a little pollen. All your remarks seem to me excellent and very interesting, and I again thank you for your kindness in writing to me. I am pleased to observe that my description of the structure of Acropera seems to agree pretty well with what you have observed. Does it not strike you as very difficult to understand how insects remove the pollinia and carry them to the stigmas? Your suggestion that the mouth of the stigmatic cavity may become charged with viscid matter and thus secure the pollinia, and that the pollen-tubes may then protrude, seems very ingenious and new to me; but it would be very anomalous in orchids, i.e. as far as I have seen. No doubt, however, though I tried my best, I shall be proved wrong in many points. Botany is a new subject to me. With respect to the protrusion of pollen-tubes, you might like to hear (if you do not already know the fact) that, as I saw this summer, in the little imperfect flowers of Viola and Oxalis, which never open, the pollen-tubes always come out of the pollen-grain, whilst still in the anthers, and direct themselves in a beautiful manner to the stigma seated at some little distance. I hope that you will continue your very interesting observations.

634. TO J. SCOTT. Down, November 19th [1862]

I am much obliged for your letter, which is full of interesting matter. I shall be very glad to look at the capsule of the Acropera when ripe, and pray present my thanks to Mr. MacNab. (634/1. See Letter 608 (Lindley, December 15th, 1861). Also "Fertilisation of Orchids," Edition II., page 172, for an account of the observations on Acropera which were corrected by Scott.) I should like to keep it till I could get a capsule of some other member of the Vandeae for comparison, but ultimately all the seeds shall be returned, in case you would like to write any notice on the subject. It was, as I said (634/2. Letter 633.), only "in desperation" that I suggested that the flower might be a male and occasionally capable of producing a few seeds. I had forgotten Gartner's remark; in fact, I know only odds and ends of Botany, and you know far more. One point makes the above view more probable in Acropera than in other cases, viz. the presence of rudimentary placentae or testae, for I cannot hear that these have been observed in the male plants. They do not occur in male Lychnis dioica, but next spring I will look to male holly flowers. I fully admit the difficulty of similarity of stigmatic chamber in the two Acroperas. As far as I remember, the blunt end of pollen-mass would not easily even stick in the orifice of the chamber. Your view may be correct about abundance of viscid matter, but seems rather improbable. Your facts about female flowers occurring where males alone ought to occur is new to me; if I do not hear that you object, I will quote the Zea case on your authority in what I am now writing on the varieties of the maize. (634/3. See "Animals and Plants," Edition II., Volume I., page 339: "Mr. Scott has lately observed the rarer case of female flowers on a true male panicle, and likewise hermaphrodite flowers." Scott's paper on the subject is in "Trans. Bot. Soc. Edinburgh," Volume VIII. See Letter 151, Volume I.) I am glad to hear that you are now working on the most curious subject of parthenogenesis. I formerly fancied that I observed female Lychnis dioica seeded without pollen. I send by this post a paper on Primula, which may interest you. (634/4. "Linn. Soc. Journal," 1862.) I am working on the subject, and if you should ever observe any analogous case I should be glad to hear. I have added another very clever pamphlet by Prof. Asa Gray. Have you a copy of my Orchis book? If you have not, and would like one, I should be pleased to send one. I plainly see that you have the true spirit of an experimentalist and good observer. Therefore, I ask whether you have ever made any trials on relative fertility of varieties of plants (like those I quote from Gartner on the varieties of Verbascum). I much want information on this head, and on those marvellous cases (as some Lobelias and Crinum passiflora) in which a plant can be more easily fertilised by the pollen of another species than by its own good pollen. I am compelled to write in haste. With many thanks for your kindness.

635. TO J. SCOTT. Down, 20th [1862?]

What a magnificent capsule, and good Heavens, what a number of seeds! I never before opened pods of larger orchids. It did not signify a few seed being lost, as it would be hopeless to estimate number in comparison with other species. If you sow any, had you not better sow a good many? so I enclose small packet. I have looked at the seeds; I never saw in the British orchids nearly so many empty testae; but this goes for nothing, as unnatural conditions would account for it. I suspect, however, from the variable size and transparency, that a good many of the seeds when dry (and I have put the capsule on my chimney-piece) will shrivel up. So I will wait a month or two till I get the capsule of some large Vandeae for comparison. It is more likely that I have made some dreadful blunder about Acropera than that it should be male yet not a perfect male. May there be some sexual relation between A. Loddigesii and luteola; they seem very close? I should very much like to examine the capsule of the unimpregnated flower of A. Loddigesii. I have got both species from Kew, but whether we shall have skill to flower them I know not. One conjectures that it is imperfect male; I still should incline to think it would produce by seed both sexes. But you are right about Primula (and a very acute thought it was): the long-styled P. sinensis, homomorphically fertilised with own-form pollen, has produced during two successive homomorphic generations only long-styled plants. (635/1. In "Forms of Flowers," Edition II., page 216, a summary of the transmission of forms in the "homomorphic" unions of P. sinensis is given. Darwin afterwards used "illegitimate" for homomorphic, and "legitimate" for "heteromorphic" ("Forms of Flowers," Edition i., page 24).) The short-styled the same, i.e. produced short-styled for two generations with the exception of a single plant. I cannot say about cowslips yet. I should like to hear your case of the Primula: is it certainly propagated by seed?

636. TO J. SCOTT. Down, December 3rd, [1862?]

What a capital observer you are! and how well you have worked the primulas. All your facts are new to me. It is likely that I overrate the interest of the subject; but it seems to me that you ought to publish a paper on the subject. It would, however, greatly add to the value if you were to cover up any of the forms having pistil and anther of the same height, and prove that they were fully self-fertile. The occurrence of dimorphic and non-dimorphic species in the same genus is quite the same as I find in Linum. (636/1. Darwin finished his paper on Linum in December 1862, and it was published in the "Linn. Soc. Journal" in 1863.) Have any of the forms of Primula, which are non-dimorphic, been propagated for some little time by seed in garden? I suppose not. I ask because I find in P. sinensis a third rather fluctuating form, apparently due to culture, with stigma and anthers of same height. I have been working successive generations homomorphically of this Primula, and think I am getting curious results; I shall probably publish next autumn; and if you do not (but I hope you will) publish yourself previously, I should be glad to quote in abstract some of your facts. But I repeat that I hope you will yourself publish. Hottonia is dimorphic, with pollen of very different sizes in the two forms. I think you are mistaken about Siphocampylus, but I feel rather doubtful in saying this to so good an observer. In Lobelia the closed pistil grows rapidly, and pushes out the pollen and then the stigma expands, and the flower in function is monoecious; from appearance I believe this is the case with your plant. I hope it is so, for this plant can hardly require a cross, being in function monoecious; so that dimorphism in such a case would be a heavy blow to understanding its nature or good in all other cases. I see few periodicals: when have you published on Clivia? I suppose that you did not actually count the seeds in the hybrids in comparison with those of the parent-forms; but this is almost necessary after Gartner's observations. I very much hope you will make a good series of comparative trials on the same plant of Tacsonia. (636/2. See Scott in "Linn. Soc. Journal," VIII.) I have raised 700-800 seedlings from cowslips, artificially fertilised with care; and they presented not a hair's-breadth approach to oxlips. I have now seed in pots of cowslip fertilised by pollen of primrose, and I hope they will grow; I have also got fine seedlings from seed of wild oxlips; so I hope to make out the case. You speak of difficulties on Natural Selection: there are indeed plenty; if ever you have spare time (which is not likely, as I am sure you must be a hard worker) I should be very glad to hear difficulties from one who has observed so much as you have. The majority of criticisms on the "Origin" are, in my opinion, not worth the paper they are printed on. Sir C. Lyell is coming out with what, I expect, will prove really good remarks. (636/3. Lyell's "Antiquity of Man" was published in the spring of 1863. In the "Life and Letters," Volume III., pages 8, 11, Darwin's correspondence shows his deep disappointment at what he thought Lyell's half-heartedness in regard to evolution. See Letter 164, Volume I.) Pray do not think me intrusive; but if you would like to have any book I have published, such as my "Journal of Researches" or the "Origin," I should esteem it a compliment to be allowed to send it. Will you permit me to suggest one experiment, which I should much like to see tried, and which I now wish the more from an extraordinary observation by Asa Gray on Gymnadenia tridentata (in number just out of Silliman's N. American Journal) (636/4. In Gymnadenia tridentata, according to Asa Gray, the anther opens in the bud, and the pollen being somewhat coherent falls on the stigma and on the rostellum which latter is penetrated by the pollen-tubes. "Fertilisation of Orchids," Edition II., page 68. Asa Gray's papers are in "American Journal of Science," Volume XXXIV., 1862, and XXXVI., 1863.); namely, to split the labellum of a Cattleya, or of some allied orchis, remove caudicle from pollen-mass (so that no loose grains are about) and put it carefully into the large tongue-like rostellum, and see if pollen-tubes will penetrate, or better, see if capsule will swell. Similar pollen-masses ought to be put on true stigmas of two or three other flowers of same plants for comparison. It is to discover whether rostellum yet retains some of its primordial function of being penetrated by pollen-tubes. You will be sorry that you ever entered into correspondence with me. But do not answer till at leisure, and as briefly as you like. My handwriting, I know, is dreadfully bad. Excuse this scribbling paper, as I can write faster on it, and I have a rather large correspondence to keep up.

637. TO J. SCOTT. Down, January 21st, 1863

I thank you for your very interesting letter; I must answer as briefly as I can, for I have a heap of other letters to answer. I strongly advise you to follow up and publish your observations on the pollen-tubes of orchids; they promise to be very interesting. If you could prove what I only conjectured (from state of utriculi in rostellum and in stigma of Catasetum and Acropera) that the utriculi somehow induce, or are correlated with, penetration of pollen-tubes you will make an important physiological discovery. I will mention, as worth your attention (and what I have anxiously wished to observe, if time had permitted, and still hope to do)--viz., the state of tissues or cells of stigma in an utterly sterile hybrid, in comparison with the same in fertile parent species; to test these cells, immerse stigmas for 48 hours in spirits of wine. I should expect in hybrids that the cells would not show coagulated contents. It would be an interesting discovery to show difference in female organs of hybrids and pure species. Anyhow, it is worth trial, and I recommend you to make it, and publish if you do. The pollen-tubes directing themselves to stigma is also very curious, though not quite so new, but well worth investigation when you get Cattleya, etc., in flower. I say not so new, for remember small flowers of Viola and Oxalis; or better, see Bibliography in "Natural History Review," No. VIII., page 419 (October, 1862) for quotation from M. Baillon on pollen-tubes finding way from anthers to stigma in Helianthemum. I should doubt gum getting solid from [i.e. because of] continued secretion. Why not sprinkle fresh plaster of Paris and make impenetrable crust? (637/1. The suggestion that the stigma should be covered with a crust of plaster of Paris, pierced by a hole to allow the pollen-tubes to enter, bears a resemblance to Miyoshi's experiments with germinating pollen and fungal spores. See "Pringsheim's Jahrbucher," 1895; "Flora," 1894.) You might modify experiment by making little hole in one lower corner, and see if tubes find it out. See in my future paper on Linum pollen and stigma recognising each other. If you will tell me that pollen smells the stigma I will try and believe you; but I will not believe the Frenchman (I forget who) who says that stigma of Vanilla actually attracts mechanically, by some unknown force, the solid pollen-masses to it! Read Asa Gray in 2nd Review of my Orchis book on pollen of Gymnadenia penetrating rostellum. I can, if you like, lend you these Reviews; but they must be returned. R. Brown, I remember, says pollen-tubes separate from grains before the lower ends of tubes reach ovules. I saw, and was interested by, abstract of your Drosera paper (637/2. A short note on the irritability of Drosera in the "Trans. Bot. Soc. Edin." Volume VII.); we have been at very much the same work.

638. TO J. SCOTT. Down, February 16th [1863]

Absence from home has prevented me from answering you sooner. I should think that the capsule of Acropera had better be left till it shows some signs of opening, as our object is to judge whether the seeds are good; but I should prefer trusting to your better judgment. I am interested about the Gongora, which I hope hereafter to try myself, as I have just built a small hot-house.

Asa Gray's observations on the rostellum of Gymnadenia are very imperfect, yet worth looking at. Your case of Imatophyllum is most interesting (638/1. A sucker of Imatophyllum minatum threw up a shoot in which the leaves were "two-ranked instead of four-ranked," and showed other differences from the normal.--"Animals and Plants," Edition II., Volume I., page 411.); even if the sport does not flower it will be worth my giving. I did not understand, or I had forgotten, that a single frond on a fern will vary; I now see that the case does come under bud-variation, and must be given by me. I had thought of it only as proof [of] inheritance in cryptogams; I am much obliged for your correction, and will consult again your paper and Mr. Bridgeman's. (638/2. The facts are given in "Animals and Plants," Edition II., Volume I., page 408.) I enclose varieties of maize from Asa Gray. Pray do not thank me for trusting you; the thanks ought to go the other way. I felt a conviction after your first letter that you were a real lover of Natural History.

If you can advance good evidence showing that bisexual plants are more variable than unisexual, it will be interesting. I shall be very glad to read the discussion which you are preparing. I admit as fully as any one can do that cross-impregnation is the great check to endless variability; but I am not sure that I understand your view. I do not believe that the structure of Primula has any necessary relation to a tendency to a dioecious structure, but seeing the difference in the fertility of the two forms, I felt bound unwillingly to admit that they might be a step towards dioeciousness; I allude to this subject in my Linum paper. (638/3. "Linn. Soc. Journal," 1863.) Thanks for your answers to my other queries. I forgot to say that I was at Kew the other day, and I find that they can give me capsules of several Vandeae.

639. TO J. SCOTT. Down, March 24th [1863]

Your letter, as every one you have written, has greatly interested me. If you can show that certain individual Passifloras, under certain known or unknown conditions of life, have stigmas capable of fertilisation by pollen from another species, or from another individual of its own species, yet not by its own individual pollen (its own individual pollen being proved to be good by its action on some other species), you will add a case of great interest to me; and which in my opinion would be quite worth your publication. (639/1. Cases nearly similar to those observed by Scott were recorded by Gartner and Kolreuter, but in these instances only certain individuals were self-impotent. In "Animals and Plants," Edition II., Volume II., page 114, where the phenomenon is fully discussed, Scott's observations ("Trans. Bot. Soc. Edin." 1863) are given as the earliest, except for one case recorded by Lecoq ("Fecondation," 1862). Interesting work was afterwards done by Hildebrand and Fritz Muller, as illustrated in many of the letters addressed to the latter.) I always imagined that such recorded cases must be due to unnatural conditions of life; and think I said so in the "Origin." (639/2. See "Origin of Species," Edition I., page 251, for Herbert's observations on self-impotence in Hippeastrum. In spite of the uniformness of the results obtained in many successive years, Darwin inferred that the plants must have been in an "unnatural state.") I am not sure that I understand your result, [nor] whether it means what I have above obscurely expressed. If you can prove the above, do publish; but if you will not publish I earnestly beg you to let me have the facts in detail; but you ought to publish, for I may not use the facts for years. I have been much interested by what you say on the rostellum exciting pollen to protrude tubes; but are you sure that the rostellum does excite them? Would not tubes protrude if placed on parts of column or base of petals, etc., near to the stigma? Please look at the "Cottage Gardener" (or "Journal of Horticulture") (639/3. "Journal of Horticulture" and "Cottage Gardener," March 31st, 1863. A short note describing Cruger's discovery of self-fertilisation in Cattleya, Epidendrum, etc., and referring to the work of "an excellent observer, Mr. J. Scott." Darwin adds that he is convinced that he has underrated the power of tropical orchids occasionally to produce seeds without the aid of insects.) to be published to-morrow week for letter of mine, in which I venture to quote you, and in which you will see a curious fact about unopened orchid flowers setting seed in West Indies. Dr. Cruger attributes protrusion of tubes to ants carrying stigmatic secretion to pollen (639/4. In Cruger's paper ("Linn. Soc. Journ." VIII., 1865; read March 3rd 1864) he speaks of the pollen-masses in situ being acted on by the stigmatic secretion, but no mention is made of the agency of ants. He describes the pollen-tubes descending "from the [pollen] masses still in situ down into the ovarian canal."); but this is mere hypothesis. Remember, pollen-tubes protrude within anther in Neottia nidus-avis. I did think it possible or probable that perfect fertilisation might have been effected through rostellum. What a curious case your Gongora must be: could you spare me one of the largest capsules? I want to estimate the number of seed, and try my hand if I can make them grow. This, however, is a foolish attempt, for Dr. Hooker, who was here a day or two ago, says they cannot at Calcutta, and yet imported species have seeded and have naturally spread on to the adjoining trees! Dr. Cruger thinks I am wrong about Catasetum: but I cannot understand his letter. He admits there are three forms in two species; and he speaks as if the sexes were separate in some and that others were hermaphrodites (639/5. Cruger ("Linn. Soc. Journal," VIII., page 127) says that the apparently hermaphrodite form is always sterile in Trinidad. Darwin modified his account in the second edition of the orchid book.); but I cannot understand what he means. He has seen lots of great humble-bees buzzing about the flowers with the pollinia sticking to their backs! Happy man!! I have the promise, but not yet surety, of some curious results with my homomorphic seedling cowslips: these have not followed the rule of Chinese Primula; homomorphic seedlings from short-styled parent have presented both forms, which disgusts me.

You will see that I am better; but still I greatly fear that I must have a compulsory holiday. With sincere thanks and hearty admiration at your powers of observation...

My poor P. scotica looks very sick which you so kindly sent me. (639/6. Sent by Scott, January 6th, 1863.)

640. TO J. SCOTT. April 12th [1863]

I really hardly know how to thank you enough for your very interesting letter. I shall certainly use all the facts which you have given me (in a condensed form) on the sterility of orchids in the work which I am now slowly preparing for publication. But why do you not publish these facts in a separate little paper? (640/1. See Letter 642, note, for reference to Scott's paper.) They seem to me well worth it, and you really ought to get your name known. I could equally well use them in my book. I earnestly hope that you will experiment on Passiflora, and let me give your results. Dr. A. Gray's observations were made loosely; he said in a letter he would attend this summer further to the case, which clearly surprised him much. I will say nothing about the rostellum, stigmatic utriculi, fertility of Acropera and Catasetum, for I am completely bewildered: it will rest with you to settle these points by your excellent observations and experiments. I must own I never could help doubting Dr. Hooker's case of the poppy. You may like to hear what I have seen this morning: I found (640/2. See Letter 658.) a primrose plant with flowers having three pistils, which when pulled asunder, without any tearing, allowed pollen to be placed on ovules. This I did with three flowers--pollen-tubes did not protrude after several days. But this day, the sixteenth (N.B.--primulas seem naturally slowly fertilised), I found many tubes protruded, and, what is very odd, they certainly seemed to have penetrated the coats of the ovules, but in no one instance the foramen of the ovule!! I mention this because it directly bears on your explanation of Dr. Cruger's case. (640/3. Cruger's case here referred to is doubtless the cleistogamic fertilisation of Epidendrum, etc. Scott discusses the question of self-fertilisation at great length in a letter to Darwin dated April, and obviously written in 1863. In Epidendrum he observed a viscid matter extending from the stigmatic chamber to the anther: pollen-tubes had protruded from the anther not only where it was in contact with the viscid matter, but also from the central part, and these spread "over the anterior surface of the rostellum downward into the stigma." Cruger believed the viscid matter reaching the anther was a necessary condition for the germination of the pollen-grains. Scott points out that the viscid matter is produced in large quantity only after the pollen-grains have penetrated the stigma, and that it is, in fact, a consequence, not a preliminary to fertilisation. He finally explains Cruger's case thus: "The greater humidity and equability of temperature consequent on such conditions [i.e. on the flowers being closed] is, I believe, the probable cause of these abnormally conditioned flowers so frequently fertilising themselves." Scott also calls attention to the danger of being deceived by fungal hyphae in observations on germination of pollen.) I believe that your explanation is right; I should never have thought of it; yet this was stupid of me, for I remember thinking that the almost closed imperfect flowers of Viola and Oxalis were related to the protrusion of the pollen-tubes. My case of the Aceras with the aborted labellum squeezed against stigma supports your view. (640/4. See "Fertilisation of Orchids," Edition II., page 258: the pollen germinated within the anther of a monstrous flower.) Dr. Cruger's notion about the ants was a simple conjecture. About cryptogamic filaments, remember Dr. C. says that the unopened flowers habitually set fruit. I think that you will change your views on the imperfect flowers of Viola and Oxalis...

642. TO J. SCOTT. May 2nd [1863]

I have left home for a fortnight to see if I can, with little hope, improve my health. The parcel of orchid pods, which you have so kindly sent me, has followed me. I am sure you will forgive the liberty which I take in returning you the postage stamps. I never heard of such a scheme as that you were compelled to practise to fertilise the Gongora! (642/1. See "Fertilisation of Orchids," Edition, II., page 169. "Mr. Scott tried repeatedly, but in vain, to force the pollen-masses into the stigma of Gongora atro-purpurea and truncata; but he readily fertilised them by cutting off the clinandrum and placing pollen-masses on the now exposed stigma.") It is a most curious problem what plan Nature follows in this genus and Acropera. (642/2. In the "Fertilisation of Orchids," Edition II., page 169, Darwin speculates as to the possible fertilisation of Acropera by an insect with pollen-masses adhering to the extremity of its abdomen. It would appear that this guess (which does not occur in the first edition) was made before he heard of Cruger's observation on the allied genus Gongora, which is visited by a bee with a long tongue, which projects, when not in use, beyond and above the tip of the abdomen. Cruger believes that this tongue is the pollinating agent. Cruger's account is in the "Journal of the Linn. Soc." VIII., 1865, page 130.) Some day I will try and estimate how many seeds there are in Gongora. I suppose and hope you have kept notes on all your observations on orchids, for, with my broken health and many other subjects, I do not know whether I shall ever have time to publish again; though I have a large collection of notes and facts ready. I think you show your wisdom in not wishing to publish too soon; a young author who publishes every trifle gets, sometimes unjustly, to be disregarded. I do not pretend to be much of a judge; but I can conscientiously say that I have never written one word to you on the merit of your letters that I do not fully believe in. Please remember that I should very much wish for a copy of your paper on sterility of individual orchids (642/3. "On the Individual Sterility and Cross-Impregnation of Certain Species of Oncidium." [Read June 2nd, 1864.] "Linn. Soc. Journal," VIII., 1865. This paper gives a full account of the self-sterility of Oncidium in cases where the pollen was efficient in fertilising other individuals of the same species and of distinct species. Some of the facts were given in Scott's paper, "Experiments on the Fertilisation of Orchids in the Royal Botanic Garden of Edinburgh," published in the "Proc. Bot. Soc. Edinb." 1863. It is probably to the latter paper that Darwin refers.) and on Drosera. (642/4. "Trans. Bot. Soc. Edinburgh," Volume VII.) Thanks for [note] about Campanula perfoliata. I have asked Asa Gray for seeds, to whom I have mentioned your observations on rostellum, and asked him to look closer to the case of Gymnadenia. (642/5. See "Fertilisation of Orchids," Edition II., page 68.) Let me hear about the sporting Imatophyllum if it flowers. Perhaps I have blundered about Primula; but certainly not about mere protrusion of pollen-tubes. I have been idly watching bees of several genera and diptera fertilising O. morio at this place, and it is a very pretty sight. I have confirmed in several ways the entire truth of my statement that there is no vestige of nectar in the spur; but the insects perforate the inner coat. This seems to me a curious little fact, which none of my reviewers have noticed.

643. TO J.D. HOOKER. 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?

644. TO JOHN SCOTT. 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.

645. TO J. SCOTT. 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.

646. TO J. SCOTT. 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.

647. TO J. SCOTT. 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.

648. TO J. SCOTT. 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.)

649. TO J. SCOTT. 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?

650. TO J.D. HOOKER. 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.

651. TO J. SCOTT. 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.

652. TO J.D. HOOKER. 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.

653. TO ASA GRAY. 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. TO J.D. HOOKER

(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 points.

What will Sir William say?

655. TO J.D. HOOKER. 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!

656. TO J.D. HOOKER. [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.)

657. TO J. SCOTT. 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.

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.

658. TO D. OLIVER. 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?

659. TO D. OLIVER. 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.

660. TO MAXWELL MASTERS. 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 the two forms of Peloria WHEN OCCURRING IN THE VERY SAME SPECIES as 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. TO P.H. GOSSE

(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.

662. TO J.D. HOOKER. 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!

663. TO D. OLIVER. 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.)

664. TO J.D. HOOKER. 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. TO T.H. HUXLEY

(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 master.

666. TO J.D. HOOKER. [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.")

667. TO J.D. HOOKER. 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.

668. TO J.D. HOOKER. 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. TO J.D. HOOKER

(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?

670. TO F. HILDEBRAND. 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.

(PLATE: FRITZ MULLER.)

2.XI.II. CORRESPONDENCE WITH FRITZ MULLER, 1865-1881.

(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.)

671. TO F. MULLER. 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 sketches.

672. TO F. MULLER

(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 hermit.

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?"

673. TO F. MULLER. 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.

674. TO F. MULLER. 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.

675. TO F. MULLER. 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.

676. TO F. MULLER. 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. TO F. MULLER

(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.

678. TO F. MULLER. 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.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

687. F. MULLER TO CHARLES DARWIN

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

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

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

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

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

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

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 paraheliotropic.

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 follows:--

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 _______________________________________________

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