Will Mr. Beaton, who has made such a multitude of most interesting observations on the propagation of plants, have the kindness to state whether varieties of the same species of Composite plants frequently cross each other by insect agency or other means?³ For instance, will any of the Cinerarias, if kept apart from other varieties, breed true? but if standing near other varieties, will they generally, or almost certainly, produce a much greater diversity of coloured seedlings?

I saw an allusion by Mr. Beaton to this subject in The Cottage Gardener of last year with respect to Zinnias;⁴ and from this allusion I infer that Zinnia sports much when kept separate.

As I am begging for information on the natural crossing of plants, I will likewise venture to inquire whether the great raisers of Hollyhocks find it necessary to keep each variety far separate from the others for raising seed. The late famous horticulturist, the Hon. and Rev. W. Herbert, when I visited him at Spofforth many years ago, remarked that he was much surprised (considering the structure of the flower and the relative periods of maturity of the pollen and stigma) how true some sorts of Hollyhocks bred, even when growing close to other varieties.⁵ I have found this to be the case with some of the varieties, and cannot understand how it is possible. Mr. Beaton might, if he pleased, write an article, very valuable to physiological botanists and of some practical utility, on the natural crossing of varieties.⁶ He might indicate in which genera crossing most commonly occurred, and in which it seldom or never occurred. For instance, I have observed Sweet Peas during several years and believe that they never cross;⁷ and it is not easy to make an artificial cross, though I succeeded at last, but got no good in a horticultural point of view.—

Charles Darwin, Down, Bromley, Kent.