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Darwin Correspondence Project

To Isaac Anderson-Henry   2 May [1863]1


May 2nd. 1863.

My dear Sir,

I have left home for a little change and your kind letter has followed me.—3 You think far too highly of my paper on Linum etc.4 I agree that subject is only beginning. I write now partly to say that I am convinced (but evidence too long) that graduated length of stamens in same flower has no relation to powers of fertilization, at least in most cases.

For scarlet dwarf


Pelargonium, if B represents the ordinary graduated stamens, you will find occasionally an additional and abnormal stamen (A) 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.5

I observed fluctuations in length of pistil in Phloxes, but thought it was mere variability.6

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.—7

I am very glad to hear that you intend working at Linum.8

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 Compounds without the simple microscope is absolutely injurious to progress of Natural History (excepting, of course, with Infusoria).9 I have, as yet, found no exception to the rule, that when a man has told me he works with Compounds alone, his work is valueless.

With my best thanks. | My dear Sir, | Yours very faithfully. | C. Darwin.


The text of the letter is taken from a copy made for Francis Darwin for his editions of CD’s letters (LL, ML); part of the letter was published in ML 2: 298–9. The copyist dated the letter 2 May 1863; however, when Francis edited the transcription he added square brackets in pencil to indicate that the year had been added by the copyist and was not present in the original letter. The year is confirmed by the relationship between this letter and the letter from Isaac Anderson-Henry, 24 April 1863.
Hartfield Grove, Hartfield, Sussex, was the home of Charles Langton, widower of Emma Darwin’s sister Charlotte. According to Emma Darwin’s diary (DAR 242), the Darwins stayed at Hartfield between 27 April and 6 May 1863.
Anderson-Henry’s name appears on CD’s presentation list for ‘Two forms in species of Linum (see Correspondence vol. 11, Appendix IV).
CD had suggested that Anderson-Henry make systematic experiments to test the reliability of Donald Beaton’s statement (Beaton 1861) that the pollen from the two shortest stamens of scarlet Pelargonium produced dwarf plants (see letter to Isaac Anderson-Henry, 20 January [1863]).
CD’s notes on ‘Spring Phlox’, dated 3 May 1863, are in DAR 49: 90. These observations formed part of a study on dichogamy (see letter from C. W. Crocker, 1[–4] May 1863, n. 4). CD published his observations on Phlox subulata as part of a discussion of heterostyled dimorphic plants in Forms of flowers, pp. 119–20.
CD possessed both a simple microscope and a compound microscope, and had long held the view that these instruments should be used together in scientific work (see Correspondence vol. 4, letter to J. D. Hooker, [1 May 1847], and letter to Richard Owen, [26 March 1848], and Correspondence vol. 5, letter to J. D. Dana, 6 December [1853]). In the simple microscope, the magnified image of the object passed directly to the eye of the observer, but in the compound microscope, a first image produced by the object-lens was focused within the tube of the microscope, and then magnified by one or more lenses forming the eye-piece (Beale 1861, p. 5). Although compound microscopes were capable of higher magnification, the direct image produced by the simple microscope made it easier to use for experimental manipulation or dissecting work. Work with the tiny unicellular ‘Infusoria’, however, would have required the resolving power of the compound microscope. CD used a simple microscope designed to his own specifications by the instrument makers Smith, Beck & Beck; the model was afterwards produced by the company for general sale as ‘Darwin’s Single Microscope’ (see Correspondence vol. 4, letter to Richard Owen, [26 March 1848] and n. 2, and Correspondence vol. 10, letter to J. D. Hooker, 22 [August 1862] and n. 13). On CD’s use of the microscope, see Burnett 1992.


Beale, Lionel Smith. 1861. How to work with the microscope: a course of lectures on the practical use of the instrument and microscopical manipulation. London: John Churchill.

Beaton, Donald. 1861. Fertilisation of wheat. Journal of Horticulture n.s. 1: 311–13.

Burnett, William A. S. 1992. Darwin’s microscopes. Microscopy: the Journal of the Quekett Microscopical Club 36: 604–27.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Forms of flowers: The different forms of flowers on plants of the same species. By Charles Darwin. London: John Murray. 1877.

LL: The life and letters of Charles Darwin, including an autobiographical chapter. Edited by Francis Darwin. 3 vols. London: John Murray. 1887–8.

ML: More letters of Charles Darwin: a record of his work in a series of hitherto unpublished letters. Edited by Francis Darwin and Albert Charles Seward. 2 vols. London: John Murray. 1903.

‘Two forms in species of Linum’: On the existence of two forms, and on their reciprocal sexual relation, in several species of the genus Linum. By Charles Darwin. [Read 5 February 1863.] Journal of the Proceedings of the Linnean Society (Botany) 7 (1864): 69–83. [Collected papers 2: 93–105.]


Convinced length of stamens has no relation to powers of fertilisation in many plants.

Suggests experiments on Pelargonium and Phlox.

Advises about use of microscope.

Letter details

Letter no.
Charles Robert Darwin
Isaac Anderson/Isaac Anderson Henry
Sent from
Charles Langton, Hartfield
Source of text
DAR 145: 3
Physical description

Please cite as

Darwin Correspondence Project, “Letter no. 4136,” accessed on 5 March 2021,

Also published in The Correspondence of Charles Darwin, vol. 11