RECORD: Darwin, C. R. 1861. Cause of the variation of flowers. Journal of Horticulture and Cottage Gardener 1 (18 June): 211.
REVISION HISTORY: Scanned, OCRed, corrected and edited by John van Wyhe 2003-8, textual corrections by Sue Asscher 1.2007. RN3
CAUSE OF THE VARIATION OF FLOWERS.
"D" OF Deal,1 states, and, apparently, he is corroborated by Mr. Lightbody,2 that when Auriculas throw up side blooms these keep pretty true to their character; but that when they throw up a heart bloom—that is, from the axis of the plant, the flower, no matter what may be the colour of its edging, "is just as likely to come in any other class as in the one it belongs to." This seems to be an extremely curious observation. It shows that some little light could be thrown on the laws of variation, if the many acute observers who read THE JOURNAL OF HORTICULTURE would contribute their knowledge on such points. I wish "D." would have the kindness to give a few more details, such as out of so many heart blooms so many lost their character, and so many kept true; giving also the proportion in the side blooms which kept true.
As I am appealed to, I will make a few observations on this subject; but I have no doubt others could throw more light on the question. Professor Moquin-Tandon asserts,3 that with irregular flowers, as Snapdragons, the terminal flower in the axis of the plant is more apt to become regular, or peloric as botanists say, than the other flowers. I once found a Laburnum tree with the terminal flower on each raceme nearly regular, having lost its peablossom structure. With many Pelargoniums (I have one at present in my greenhouse, but I know not its name), the central flower in each truss every year comes regular, loses the two dark patches of colour on the two upper petals, and, what is very curious, loses the nectary, which may be seen in all the other flowers cohering to the flower-stalk. In the common Carrot the central floret in the umbel is dark purple and very different from the others; and I find that this central little flower is extremely variable. Are there not other cases of species which habitually have the central flower different from the others? It must, however, be confessed, that Mr. Masters,4 a high authority on such subjects, disputes that peloric flowers are apt to be central; but it seems to me extremely improbable that the several recorded cases should be due to chance, and all these facts seem to hang together and to indicate that in the flower nearest the axis there is a tendency to differ from the others, or to be variable, or to revert to a hypothetical regular form—that is, as I should look at it, to revert to the structure of a remote ancestor. The curious case of the Auricula apparently falls into this same group of facts.
I hope that some of your correspondents will state whether in the case of single buds sporting, as has so often occurred with Pelargoniums, it has been observed that such sports occur more frequently on one part of the plant than on another. I suppose it is not so, or it would have been noted. Having alluded to the central flower in certain Pelargoniums which have lost the two dark patches of colour and the nectary, I would venture to ask some skilful observer to try whether this flower could be made by artificial fertilisation and by pulling off some of the adjoining flowers to yield seed. The stigma should be fertilised with pollen from, if possible, a peloric flower on another plant; and access of other pollen should, of course, be prevented. Peloric flowers have generally been found quite sterile; but Willdenow5 got seeds from a peloric Snapdragon, and the peculiarity was inherited: hence it is possible, though not probable, that a new strain of quite symmetrically-flowered Pelargoniums might be thus raised. Experiments are tedious and very often fail; but it would be well worth while for any man endowed with plenty of patience to collect seed from the central floret and from the other florets on the same truss of any ordinary Pelargonium, and sow them separately and see which varied most. Of course, all the flowers should be fertilised by the same pollen and subsequently protected from insects.
The same law which causes the heart bloom on an individual Auricula not to keep so true as a side bloom, might cause the seedlings of the central flower of a Pelargonium or other plant to vary more than the seedlings from the other and exterior flowers. This would be a secret worth discovering and revealing.—CHARLES DARWIN, Down, Bromley, Kent.
1 D. of Deal 1861 queried: 'How comes it to pass, that if an Auricula throws up a side bloom it is pretty sure to be in character; but that if it be from the heart of the flower ... it is just as likely to come in any other class as the one it belongs to? ... Can Mr. Darwin, Mr. Beaton, or anybody enlighten me on the first of these points?' See Correspondence vol. 9, pp. 179-181.
2 George Lightbody (d. 1872), gardener and member of the Falkirk Horticultural Society, Scotland, who raised numerous Auricula varieties.
3 Horace Bénédict Alfred Moquin-Tandon (1804-1863), French botanist and naturalist. Moquin-Tandon 1841, p. 192.
4 Maxwell Tylden Masters (1833-1907), botanist and physician; editor of the Gardeners' Chronicle, 1865-1907.
5 Karl Ludwig Willdenow (1765-1812), German botanist and pharmacist.
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Citation: John van Wyhe, editor. 2002-. The Complete Work of Charles Darwin Online. (http://darwin-online.org.uk/)
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