(150/1. The following is the first of a series of letters addressed to the late John Scott, of which the major part is given in our Botanical chapters. We have been tempted to give this correspondence fully not only because of its intrinsic scientific interest, but also because they are almost the only letters which show Darwin in personal relation with a younger man engaged in research under his supervision.)
To the best of my judgment, no subject is so important in relation to theoretical natural science, in several respects, and likewise in itself deserving investigation, as the effects of changed or unnatural conditions, or of changed structure on the reproductive system. Under this point of view the relation of well-marked but undoubted varieties in fertilising each other requires far more experiments than have been tried. See in the "Origin" the brief abstract of Gartner on Verbascum and Zea. Mr. W. Crocker, lately foreman at Kew and a very good observer, is going at my suggestion to work varieties of hollyhock. (150/2. Altheae species. These experiments seem not to have been carried out.) The climate would be too cold, I suppose, for varieties of tobacco. I began on cabbages, but immediately stopped from early shedding of their pollen causing too much trouble. Your knowledge would suggest some [plants]. On the same principle it would be well to test peloric flowers with their own pollen, and with pollen of regular flowers, and try pollen of peloric on regular flowers--seeds being counted in each case. I have now got one seedling from many crosses of a peloric Pelargonium by peloric pollen; I have two or three seedlings from a peloric flower by pollen of regular flower. I have ordered a peloric Antirrhinum (150/3. See "Variation of Animals and Plants," Edition I., Volume II., page 70.) and the peloric Gloxinia, but I much fear I shall never have time to try them. The Passiflora cases are truly wonderful, like the Crinum cases (see "Origin"). (150/4. "Origin," Edition VI., page 238.) I have read in a German paper that some varieties of potatoes (name not given) cannot be fertilised by [their] own pollen, but can by pollen of other varieties: well worth trying. Again, fertility of any monster flower, which is pretty regularly produced; I have got the wonderful Begonia frigida (150/5. The species on which Sir J.D. Hooker wrote in the "Gardeners' Chronicle," February 25th, 1860. See "Life and Letters," II., page 275.) from Kew, but doubt whether I have heat to set its seeds. If an unmodified Celosia could be got, it would be well to test with the modified cockscomb. There is a variation of columbine [Aquilegia] with simple petals without nectaries, etc., etc. I never could think what to try; but if one could get hold of a long-cultivated plant which crossed with a distinct species and yielded a very small number of seeds, then it would be highly good to test comparatively the wild parent-form and its varying offspring with this third species: for instance, if a polyanthus would cross with some species of Primula, then to try a wild cowslip with it. I believe hardly any primulas have ever been crossed. If we knew and could get the parent of the carnation (150/6. Dianthus caryophyllus, garden variety.), it would be very good for this end. Any member of the Lythraceae raised from seed ought to be well looked after for dimorphism.
I have wonderful facts, the result of experiment, on Lythrum salicaria.
LETTER 151. TO JOHN SCOTT. Down, December 11th .
I have read your paper with much interest. (151/1. "On the Nature and Peculiarities of the Fern-spore." "Bot. Soc. Edin." Read June 12th, 1862.) You ask for remarks on the matter, which is alone really important. Shall you think me impertinent (I am sure I do not mean to be so) if I hazard a remark on the style, which is of more importance than some think? In my opinion (whether or no worth much) your paper would have been much better if written more simply and less elaborated—more like your letters. It is a golden rule always to use, if possible, a short old Saxon word. Such a sentence as "so purely dependent is the incipient plant on the specific morphological tendency" does not sound to my ears like good mother-English--it wants translating. Here and there you might, I think, have condensed some sentences. I go on the plan of thinking every single word which can be omitted without actual loss of sense as a decided gain. Now perhaps you will think me a meddling intruder: anyhow, it is the advice of an old hackneyed writer who sincerely wishes you well. Your remark on the two sexes counteracting variability in product of the one is new to me. (151/2. Scott (op. cit., page 214): "The reproductive organs of phoenogams, as is well-known, are always products of two morphologically distinct organs, the stamens producing the pollen, the carpels producing the ovules...The embryo being in this case the modified resultant of two originally distinct organs, there will necessarily be a greater tendency to efface any individual peculiarities of these than would have been the case had the embryo been the product of a single organ." A different idea seems to have occurred to Mr. Darwin, for in an undated letter to Scott he wrote: "I hardly know what to say on your view of male and female organs and variability. I must think more over it. But I was amused by finding the other day in my portfolio devoted to bud-variation a slip of paper dated June, 1860, with some such words as these, 'May not permanence of grafted buds be due to the two sexual elements derived from different parts not having come into play?' I had utterly forgotten, when I read your paper that any analogous notion had ever passed through my mind--nor can I now remember, but the slip shows me that it had." It is interesting that Huxley also came to a conclusion differing from Scott's; and, curiously enough, Darwin confused the two views, for he wrote to Scott (December 19th): "By an odd chance, reading last night some short lectures just published by Prof. Huxley, I find your observation, independently arrived at by him, on the confluence of the two sexes causing variability." Professor Huxley's remarks are in his "Lectures to Working Men on our Knowledge, etc." No. 4, page 90: "And, indeed, I think that a certain amount of variation from the primitive stock is the necessary result of the method of sexual propagation itself; for inasmuch as the thing propagated proceeds from two organisms of different sexes and different makes and temperaments, and, as the offspring is to be either of one sex or the other, it is quite clear that it cannot be an exact diagonal of the two, or it would be of no sex at all; it cannot be an exact intermediate form between that of each of its parents--it must deviate to one side or the other.") But I cannot avoid thinking that there is something unknown and deeper in seminal generation. Reflect on the long succession of embryological changes in every animal. Does a bud ever produce cotyledons or embryonic leaves? I have been much interested by your remark on inheritance at corresponding ages; I hope you will, as you say, continue to attend to this. Is it true that female Primula plants always produce females by parthenogenesis? (151/3. It seems probable that Darwin here means vegetative reproduction.) If you can answer this I should be glad; it bears on my Primula work. I thought on the subject, but gave up investigating what had been observed, because the female bee by parthenogenesis produces males alone. Your paper has told me much that in my ignorance was quite new to me. Thanks about P. scotica. If any important criticisms are made on the Primula to the Botanical Society, I should be glad to hear them. If you think fit, you may state that I repeated the crossing experiments on P. sinensis and cowslip with the same result this spring as last year--indeed, with rather more marked difference in fertility of the two crosses. In fact, had I then proved the Linum case, I would not have wasted time in repetition. I am determined I will at once publish on Linum...
I was right to be cautious in supposing you in error about Siphocampylus (no flowers were enclosed). I hope that you will make out whether the pistil presents two definite lengths; I shall be astounded if it does. I do not fully understand your objections to Natural Selection; if I do, I presume they would apply with full force to, for instance, birds. Reflect on modification of Arab-Turk horse into our English racehorse. I have had the satisfaction to tell my publisher to send my "Journal" and "Origin" to your address. I suspect, with your fertile mind, you will find it far better to experiment on your own choice; but if, on reflection, you would like to try some which interest me, I should be truly delighted, and in this case would write in some detail. If you have the means to repeat Gartner's experiments on variations of Verbascum or on maize (see the "Origin"), such experiments would be pre-eminently important. I could never get variations of Verbascum. I could suggest an experiment on potatoes analogous with the case of Passiflora; even the case of Passiflora, often as it has been repeated, might be with advantage repeated. I have worked like a slave (having counted about nine thousand seeds) on Melastoma, on the meaning of the two sets of very different stamens, and as yet have been shamefully beaten, and I now cry for aid. I could suggest what I believe a very good scheme (at least, Dr. Hooker thought so) for systematic degeneration of culinary plants, and so find out their origin; but this would be laborious and the work of years.
LETTER 152. TO J.D. HOOKER. Down, 12th [December, 1862].
My good old Friend-How kind you have been to give me so much of your time! Your letter is of real use, and has been and shall be well considered. I am much pleased to find that we do not differ as much as I feared. I begin my book with saying that my chief object is to show the inordinate scale of variation; I have especially studied all sorts of variations of the individual. On crossing I cannot change; the more I think, the more reason I have to believe that my conclusion would be agreed to by all practised breeders. I also greatly doubt about variability and domestication being at all necessarily correlative, but I have touched on this in "Origin." Plants being identical under very different conditions has always seemed to me a very heavy argument against what I call direct action. I think perhaps I will take the case of 1,000 pigeons (152/1. See Letter 146.) to sum up my volume; I will not discuss other points, but, as I have said, I shall recur to your letter. But I must just say that if sterility be allowed to come into play, if long-beaked be in the least degree sterile with short-beaked, my whole case is altered. By the way, my notions on hybridity are becoming considerably altered by my dimorphic work. I am now strongly inclined to believe that sterility is at first a selected quality to keep incipient species distinct. If you have looked at Lythrum you will see how pollen can be modified merely to favour crossing; with equal readiness it could be modified to prevent crossing.
It is this which makes me so much interested with dimorphism, etc. (152/2. This gives a narrow impression of Darwin's interest in dimorphism. The importance of his work was (briefly put) the proof that sterility has no necessary connection with specific difference, but depends on sexual differentiation independent of racial differences. See "Life and Letters," III., page 296. His point of view that sterility is a selected quality is again given in a letter to Huxley ("Life and Letters," II., page 384), but was not upheld in his later writings (see "Origin of Species," Edition VI., page 245). The idea of sterility being a selected quality is interesting in connection with Romanes' theory of physiological selection. (See Letters 209-214.))
One word more. When you pitched me head over heels by your new way of looking at the back side of variation, I received assurance and strength by considering monsters--due to law: horribly strange as they are, the monsters were alive till at least when born. They differ at least as much from the parent as any one mammal from another.
I have just finished a long, weary chapter on simple facts of variation of cultivated plants, and am now refreshing myself with a paper on Linum for the Linnean Society.
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