[page] 143

[…] In all the four volumes of Darwin's correspondence which have been published, there is only one letter of Meehan, dated October 9, 1874, dealing with flower colors (F. Darwin and Seward, 1903 letter no, 265). Similarly, Meehan is mentioned twice by Darwin in his book The different forms of flowers on plants of the same species (1877), but not in any other of Darwin's works.

In a letter to Asa Gray, written on June 10, 1862, (1) Darwin did mention that a Mr. Meehan had sent him his paper on parallel differences in trees of North America and Europe and asked "if this can be approximately trusted for the case interests me much as [the] best case | have seen of apparently direct action of conditions of life." Actually, Meehan's whole scientific career was dominated by attempts to demonstrate the importance over any other conditioning factor of the direct action of the environment on plants. Asa Gray's reply (2), written on July 2, 1862, said "Meehan—a good gardener—send(s) me his manuscripts before printing. I tried to find exceptions to this rule, and I thought I had, but he beat me down...Meehan is an honest and I suppose very good observer and you may 'approximately' trust him, I should think. He may have got hold of something."

Nevertheless, it was just this subject of the direct effects of the environment which, 16 years later, produced the obvious symptoms of discord between Meehan and Darwin, as the following report, involving the flax genus, Linum, will show.

[…]

[page] 146

The salient part of Meehan's note is the following:

However, it is well to recognize the fact that plants, and no doubt insects, behave differently in different places. For instance, Mr. Darwin from English experiments utterly denies that Linum perenne can fertilize itself by its own pollen. He says we may as well sprinkle over it so much inorganic dust. But a single plant which I brought with me from Colorado in 1873, bears fruit freely in the garden every year. It shows how a plant may behave in one place is no rule as to how it will elsewhere . . .

In itself this would appear to be quite an innocent statement of an observation and what could be considered as one interpretation of it. But Darwin, when he read it, did not accept it as such. Through an unfortunate error, presumably by Francis Darwin, in assembling Charles Darwin's letters for publication (F. Darwin, 1896), the impact of the latter's reaction to Meehan's note and the subsequent developments have been completely obscured. The events are presented here in chronological order. Each letter is referred to in the Appendix, where the reasons for placing them in this order are discussed.

On January 21, 1878, Darwin had written (3) to Asa Gray thanking him for the review of his book, which Gray had just put out in the January issue of the American journal of science (Gray, 1878). Later he added an emotion charged postscript (4) which should be quoted in full:

P.S. I forget to add the following as I wished to do yesterday. Mr. Meehan in a paper lately read before the Philadelphia Society says in a somewhat sneering tone that plants behave differently in one country from another for that a single plant of Linum perenne brought from Colorado by him was quite fertile with him, where I state [confirmed he might have added by Hildebrand] that it is absolutely sterile with its own pollen. Now he does not state whether his plant was long-styled or short-styled, and as he speaks of bringing the plant from Colorado, I imagine that it was there endemic. Does L. perenne grow there? Dr. Alefeld says None of the true American species are heterostyled. Now if Mr. Meehan has mistaken the species it seems to me too bad to throw a slur or doubt on another man's accuracy without taking the slightest pains to be accurate himself. I have been almost tempted to write formally to the Philadelphia Society to enquire how the case really stands. But I have resolved not to do so, as Hildebrand has fully confirmed my statement... Mr. Meehan's inaccuracy seems to me injurious in no small degree to Science.

It is fortunate that Darwin did not write to the "Philadelphia Society" in view of the fact that Meehan's paper had appeared in the Bulletin of the

[page] 147

[figure]

Torrey botanical club, published in New York. Darwin's sensitivity to criticism and his willingness to unburden himself to his close friends are well known, but the intensity of his feeling here demands further explanation, as is attempted later.

Asa Gray lived up to his championship of Darwin. He had already reviewed Darwin's book in the January issue of the American journal of science, but he added a supplementary note in the March issue (Gray, 1878). This reveals, in its wording, the direct influence of Darwin's letter quoted above, proving that letter to have been written in 1878. After quoting from Meehan's note, Gray wrote,

[page] 148

This extremely remarkable induction of a general rule, —that plants and insects cannot be depended upon for behaviour,— is inferred from two instances, one of which has been sufficiently examined; and now a few words may dispose of the other. Mr. Meehan must have noticed (in Forms of Flowers, p. 92) that Darwin's result has been completely confirmed by Hildebrand; and he might have read on p. 100 the statement taken from Alefeld, that no American species is heterostyled; and on p. 100 that the Colorado plant, Linum Lewisii, of Pursh, the American representative of L. perenne, is suspected to be a distinct species, of a sort fully capable of self-fertilizing. This is what Mr. Meehan's observation goes to prove; and so, instead of showing that the behavior of species cannot be relied on, he has unwittingly brought evidence of the correctness of Mr. Darwin's surmise.

[…]

However, Darwin, who received this letter and replied to it (6) on February 17, expressing his gratitude, had not merely sought assistance from Gray. As he makes clear in this latest letter, he had also invoked the aid of his other botanical confidant, Sir Joseph Hooker. He recounts the results of the investigation which Hooker made on his behalf and this report to Gray contains a very gentle retraction of his previous view. Darwin wrote that Hooker had looked at his own specimens collected in Colorado (in 1877, during his joint trip through North America with Gray) and found that "the American form is less strongly heterostyled than the European" and that, although there is some variability, "the stamens and styles are even equal in some specimens." In this letter it is notable that Darwin still referred to these specimens as Linum perenne—as some botanists do even at the present day (e.g., Hultén, 1941-1950; Munz, 1959).

[…]

[page] 150

Despite his lapse of memory, Darwin's scientific acumen shines through. Part of his genius lay in his ability to distinguish the time and place to make an observation or perform an experiment and we should do him an injustice if another quotation were not made from his letter of February 17, 1878 (6): "If I were forced to wager I would bet that the American form would prove at least functionally a distinct species. If you could get and send me seed of the Colorado form, I would grow both forms and see if they could be crossed artificially and I would try whether the homostyled individuals were self-fertile."

[…]

[page] 154

[…]

If further evidence be needed of this growing suspicion in Darwin's mind that organisms might be acted upon by different environments in such a way that they could "behave differently in different places" (to use Meehan's words), this can be found in a letter (9) written in 1876 by Darwin to Moritz Wagner, "When I wrote the 'Origin' and for some time afterwards, I could find little good evidence of the direct action of the environment; now there is a large body of evidence..."

[…]

[page] 155

[…]

In fact, for completeness of the record, it should be noted that Darwin later found reason for a return to his old enthusiasm for natural selection rather than direct action. Less than a year before his death he wrote (10) to Professor Karl Semper (1832-1893) of Wurzburg, indicating how the careful cultivation studies on wild plants carried out by H. K. Hoffmann, in Germany in 1865, had diminished the apparent evolutionary power of direct action and indicating that this vindicated his own earlier thoughts (see item 10 in Appendix). […]

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APPENDIX

THE LETTERS FROM AND TO CHARLES DARWIN CITED IN THE TEXT

(1) Charles Darwin to Asa Gray, June 10, 1862. Reproduced in part in F. Darwin (1896), vol. 2, p. 446. The portion quoted here (p. 143), however, is not given there but is taken directly from the letter, now in the Gray collection at Harvard University. Dr. A. Hunter Dupree kindly furnished the material.

(2) Asa Gray to Charles Darwin, July 2, 1862. Quoted from Jane L. Gray (1893), vol. 2, Pp. 485.

(3) Charles Darwin to Asa Gray, January 21, 1378. See (4).

(4) In the collection of Darwin's letters to Asa Gray, at the Gray Herbarium, Harvard University, there is one letter dated "Jan. 21, 78." Two others are dated, respectively, "Jan. 20" and "Jan. 21" (the latter commencing "P.S...."). When these were collated by Francis Darwin for the production of the Life and letters, the first of them was numbered 123. The second and third were placed together and numbered 127 (with the date "1880" added in pencil). They are combined this way in both the Life and letters (F. Darwin, 1896) and in the later publication by Holbrook (1939). There can be no doubt, however, that the first and third letters are the ones which should have been combined as letter and postscript respectively. This is shown positively by Asa Gray's publication, in March 1878, of his supplementary review of Meehan's note, based on Darwin's postscript, proving the latter to have been written earlier in the same year.

Darwin's postscript, itself, contains evidence of dating, because it ends with an addendum

"I have just spent a delightful two hours at Kew, and heard prodigies of your strength and activity—that you run up a mountain like a cat!" [To Asa Gray, 21 (and 22) January 1878].

At Kew, Darwin would have met Joseph Hooker who had recently returned (in October, 1877) from travelling through the United States with Asa Gray. Contributing to the mistake in collation of these letters must have been Darwin's opening words in the postscript

"I forgot to add the following as I wished to do yesterday .. .". [To Asa Gray, 21 (and 22) January 1878].

Despite this, it is clear that the letter and the postscript to it were both given the same date, "Jan. 21." There is no question that the remaining letter (no. 127 sensu stricto) was truly written in 1880, despite the fact that Charles Darwin, himself, did not indicate the year. This is because, in this letter, Darwin refers to an illustration on page 21 of Gray's "text book" showing the seedling of Megarrhiza californica. It was not until the sixth edition of this book3 that this illustration makes its appearance on page 21, and this edition was published late in 1879.

(5) Asa Gray to Charles Darwin, February 8, 1878. This letter is referred to by Darwin in his reply dated February 17, 1878. See (6).

3 Structural botany; or organography on the basis of morphology Part 1. New York, Ivison, Blakeman, Taylor and Co., 1879.

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(6) Charles Darwin to Asa Gray, February 17, 1878. This letter (no. 129 in the Gray collection at Harvard) was not dated as to year. Its contents reveal that the year was 1878. In particular, it could not have been earlier because of the reference to Hooker's Colorado specimens, which were collected in 1877,

(7) Charles Darwin to Asa Gray, January 19, 1863. Quoted from Holbrook (1939), p. 49.

(8) Charles Darwin to John Scott, June 6, 1863. Quoted from F. Darwin and A. C. Seward (1903), vol. 2, p. 323.

(9) Charles Darwin to Moritz Wagner, October 13, 1876. Quoted from F. Darwin (1896), vol. 2, p. 338.

(10) Charles Darwin to Karl Semper (1832-1893), July 19, 1881. Quoted from F. Darwin (1896), vol. 2, pp. 516-7. This letter appears to be so important for an appreciation of Darwin's vacillation (and yet to be so neglected) that it is quoted here in extenso.

Down, July 19, 1881

My Dear Professor Semper,—

I have been much pleased to receive your letter, but I did not expect you to answer my former one. . . I cannot remember what I wrote to you, but I am sure that it must have expressed the interest which I felt in reading your book.4 I thought that you attributed too much weight to the direct action of the environment; but whether I said so I know not, for without being asked I should have thought it presumptuous to have criticised your book, nor should I now say so had I not during the last few days been struck with Professor Hoffmann's review of his own work in the 'Botanische Zeitung,' on the variability of plants; and it is really surprising how little effect he produced by cultivating certain plants under unnatural conditions, as the presence of salt, lime, zinc, etc., etc., during several generations. Plants moreover, were selected which were the most likely to vary under such conditions, judging from the existence of closely-allied forms adapted for these conditions. No doubt I originally attributed too little weight to the direct action of conditions, but Hoffmann's paper has staggered me. Perhaps hundreds of generations of exposure are necessary. It is a most perplexing subject. I wish I was not so old, and had more strength, for I see lines of research to follow. Hoffmann even doubts whether plants vary more under cultivation than in their native home and under their natural conditions. If so, the astonishing variations of almost all cultivated plants must be due to selection and breeding from the varying individuals. The idea crossed my mind many years ago, but I was afraid to publish it, as I thought people would say 'how he does exaggerate the importance of selection.' I still must believe that changed conditions give the impulse to variability, but that they act in most cases in a very indirect manner."

(II) Charles Darwin to the editor of The Gardeners' chronicle, headed ''Fertilisation of Plants," dated "February 19." In, Gard. Chron, ser. 2. 7: 246. (24 Feb.) 1887.

4 Published in the "International Scientific Series," in 1881, under the title, "The natural conditions of existence as they affect animal life."