skip to content

Darwin Correspondence Project

From John Denny   20 July 1872

Stoke Newington

July 20th. 1872

Dear Sir

In the first place allow me to thank you very much for the compliment you pay me, in suggesting that the results of my experiments in the fertilization of the Pelargonium family should be communicated to a scientific society. & more especially for your kind offer to be the medium of its communication; believe me I thoroughly appreciate both the compliment & your kindness.1

But you must permit me to observe, that it is one thing to write a paper for a Horticultural Congress, and another to do so for the Linnean Society, & moreover one worthy of your introduction.2

An undertaking I hardly feel myself qualified to attempt, at any rate before doing so it would be necessary to decide (if possible) the essential point of my case, viz, the origin of the Duke of Cornwall, & other var. in question.

From my statements it seems you assume them to be varieties only of the zonals I’ve tried to cross with them.3 if you refer to my paper, & to the Florist, you will see I speak of them as being “to all appearance but mere varieties of the zonal section”.4

Hence the difficulty I speak of in the early part of my paper.. that for the want of some distinctive evidence, or line of demarcation, we are unable to decide what are varieties, & what belong to distinct species.

There is I presume no means of ascertaining this—as regards the plants in question?

The Duke of Cornwall is a robust grower, but in all other respects, resembles both in flower & foliage—the ordinary varieties of the Scarlet section; it is a very old variety, and at present I am quite unable to trace its parentage.5

Beauté de Suresnes, & Dr. Muret are similar in habit of growth; & of french origin, so I fear their history is not easily obtained either.

These varieties may possibly have sprung from one, & a distinct parentage from the zonals I’ve tried to cross with them.6

For instance, in another section of the Pelargonium family.—the class known by the name of “Fancies” seem to be quite distinct from the class called “Show” or large flowering, for they will not cross, yet to all appearance they are sufficiently alike, to lead one to suppose them to be but varieties.7

Therefore it seems to me, that unless I could prove that these varieties I name, have descended from the same parents as those I’ve attempted to cross with them, my case is worthless.8

In answer to your remark, I would observe I have tried hundreds of times, & numerous varieties of the zonal section, to effect a cross upon, & from these Vars. failing to produce fructification in every instance, unless by using their pollen upon themselves or upon each other of these varieties. & upon, or from the double varieties which sprang from Beauté de Suresnes.

With regard to the Ivy leaved variety—Peltatum Elegans, the case is clearer, for I suppose this section of the Pelargonium family—represents a distinct species “or a supposed distinct species.” but with these I should like to continue my experiments at least another season, & to let the results become more fully developed, & more numerous, before reporting upon them to a scientific Society.

I am this season putting the pollen of Peltatum Elegans upon the zonal section—& I seem to have some seed approaching maturity from this cross; if so this variety of the Ivy-leaved section is reciprocally fertile with the zonal.

With regard to your remark respecting the exclusion of insects,—by the aid of a powerful glass,—there seems to me no difficulty in ascertaining that the stigma (in the pelargonium family) is in a state of perfect virginity, viz, that there is not a grain of pollen on it; & I assume that as soon as I have covered it completely with the desired pollen, that it is proof against the receipt of any other; or at any rate that the chances are as a thousand to one, against its becoming impregnated subsequently.9

The remarks I make in my paper—(you see) rather anticipate the probability of the influence resulting from constitution &c. &c. being different, when distinct species are employed, from my experiments on varieties, so that Gärtners conclusions may be correct without upsetting mine.10

But to be able to form any decided opinion upon the various points mooted at the commencement of my paper, we require an accumulation of reliable evidence.—& facts more distinctly given than I’ve yet seen.

I am now trying some experiments in crossing Lilies of more opposite characters, to see the effects of parentage in that family, as regards transmission of size, shape, color, & perfume.

Professor Dyer tells me he has Gärtners works in hand, but it did not appear to be clear, how soon they would be ready for publication.11

We took some steps at our meeting on Wednesday of the Roy. Horticultural Society regarding Ayrton’s scandalous conduct towards Dr. Hooker. Not at all too soon for as I took the liberty to remark, it was a disgrace to the Society not to have been the first to move in the matter12

Fearing my prodigiously long letter has long since tired you out | Believe me | Dear Sir | to remain yours faithfully | John Denny

CD annotations

15.1 With … subsequently. 15.6] 2 crosses in margin pencil

Footnotes

Denny 1872a was originally delivered at the Birmingham Horticultural Congress (see letter to John Denny, 9 July 1872 and n. 1).
The statement was made in Denny 1872a, p. 904. See also Denny 1872b, p. 52.
The scarlet section was one of the sections into which pelargoniums had been divided by Richard Colt Hoare in 1821. Hoare’s classification reflected the priorities of horticultural hybridisers rather than being based upon botanical characters (see also letter from John Denny, 12 July 1872, n. 2). The scarlet section contained some of the earliest hybrids, but there was little evidence of the origin of these plants. By the 1840s it was unclear even which plants were being referred to as scarlet pelargoniums. See Wilkinson 2007, pp. 84–6, 131–3.
From the 1850s the French had become keen pelargonium breeders and the variety ‘Beauté de Suresnes’ was widely used for the production of hybrids. Attempts were made to distinguish which of these plants were zonal pelargoniums, but in 1867 a Paris commission of horticulturists found the task impossible and instead divided the plants according to colour. See Wilkinson 2007, p. 202.
Both fancy and show pelargoniums had been developed by florists; fancy types had round flat flowers with all five petals often of the same colour and show types had large blotches on the two large upper petals (Wilkinson 2007, pp. 161–2).
One of Denny’s aims in producing as many crosses as possible in the scarlet section of pelargoniums was to determine whether the influence of the parents was the same when crossing varieties as when crossing species.
CD’s own researches had shown that this was not the case; see, for example, Variation 2: 187, and CD’s conclusions in Cross and self fertilisation, pp. 391–2.
In Denny 1872a, p. 904, Denny alluded to ‘the possible difference in the respective influence of the parents in true hybridisation’, that is, when species rather than varieties are crossed. CD had presented Karl Friedrich von Gärtner’s views in opposition to those of Denny in his letter to John Denny, 14 July [1872].
William Turner Thiselton-Dyer had presumably been asked to prepare the translation of Gärtner 1849 for the Ray Society (see also letter to John Denny, 14 July [1872] and n. 5). No translation of Gärtner’s work was published.
At a meeting of 17 July 1872, the Scientific Committee of the Royal Horticultural Society responded to Acton Smee Ayrton’s interference with the running of the Royal Botanic Gardens at Kew by resolving to support the director, Joseph Dalton Hooker, in ‘his efforts to maintain unimpaired the scientific character of Kew’ (Journal of the Royal Horticultural Society of London n.s. 4 (1877): xxx). It was further resolved that the committee would also support the memorial that was sent to William Ewart Gladstone (see letter from John Lubbock to W. E. Gladstone, 20 June 1872 and enclosure).

Bibliography

Cross and self fertilisation: The effects of cross and self fertilisation in the vegetable kingdom. By Charles Darwin. London: John Murray. 1876.

Gärtner, Karl Friedrich von. 1849. Versuche und Beobachtungen über die Bastarderzeugung im Pflanzenreich. Mit Hinweisung auf die ähnlichen Erscheinungen im Thierreiche, ganz umgearbeitete und sehr vermehrte Ausgabe der von der Königlich holländischen Akademie der Wissenschaften. Stuttgart: E. Schweizerbart.

Variation: The variation of animals and plants under domestication. By Charles Darwin. 2 vols. London: John Murray. 1868.

Wilkinson, Anne. 2007. The passion for pelargoniums: how they found their place in the garden. Stroud: Sutton Publishing.

Summary

Thanks CD for his offer to communicate the results of his experiments with Pelargonium to the Linnean Society. Prefers to continue experimenting for at least another season before doing so.

Letter details

Letter no.
DCP-LETT-8421
From
John Denny
To
Charles Robert Darwin
Sent from
Stoke Newington
Source of text
DAR 162: 160
Physical description
ALS 16pp †

Please cite as

Darwin Correspondence Project, “Letter no. 8421,” accessed on 28 March 2024, https://www.darwinproject.ac.uk/letter/?docId=letters/DCP-LETT-8421.xml

Also published in The Correspondence of Charles Darwin, vol. 20

letter