More Letters of Charles Darwin — Volume 2

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?"

LETTER 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.

LETTER 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.

LETTER 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.

LETTER 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.)

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.

LETTER 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.

LETTER 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.

LETTER 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.

LETTER 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.

LETTER 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.

LETTER 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).)

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