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DOUBLE FLOWERS—THEIR ORIGIN.

THE inclosed specimens appear to me curious, as in some degree connected with the origin of double flowers. They consist of plants of the Gentiana amarella, found in a wild state, covered with abortive buds, or rather minute double flowers. Each head consists of innumerable small petal-like purplish scales, having in their centre a tuft of still smaller green scales. A plant covered with these little heads not infrequently bears, especially near the top of the stem, one or two more perfect flowers. By examining these, a series can be shown, by which the stamens are seen to become deformed, and gradually to pass into small petals and scales. The pistil also can be traced, becoming more and more foliaceous. The change in the pistil has been effected in several flowers, whilst the stamens have remained nearly perfect. In the same manner I have observed in double Violets and some other garden flowers, that the pistil, contrary to the general rule, is metamorphosed before the stamens. In other semi-perfect flowers of the Gentiana, the divisions of the corolla and the number of the stamens, with their filaments flattened, are increased; in others, besides the five ordinary stamens, in an imperfect state, the divisions of the corolla are partially converted into stamen-like bodies: if this conversion had been effected, the flower would have become apetalous. In a Bladder-nut (Staphylea) growing in a shady wood, I last summer noticed a similar fact, namely, that the petals showed a tendency to form additional stamens. The plants of the Gentiana bearing the little tufts are generally, but not always, dwarfer than the perfect plants; their leaves are less pointed, and the entire plant is much less symmetrical. The much greater number of the imperfect flowers on one plant than are ever produced of the perfect, shows, I presume, that the metamorphic change must be determined early in the plant's life. Except in their small size, less beauty, and in the occasional presence on the same stem of flowers in different stages of monstrosity, these purple tufts seem to be essentially similar in their nature to the double flowers of Horticulturists.

The plants of the Gentiana in both states grow mingled together on a very hard, dry, bare chalk bank; but those with the abortive flowers grow on rather the barest spots, where it was surprising that anything could grow. You state in your "Theory of Horticulture,"¹ that the origin of double flowers is not well understood. Some have attributed it to excess of food; but the dry chalk bank surely was not too rich a soil; and I may mention that late last autumn, I found on an adjoining field of wretchedly sterile clay, great numbers of the Ranunculus repens, producing semi-double flowers, some having three, some additional rows of petals. The partial or entire sterility of double flowers is generally attributed to their doubleness; but is not this putting the effect before the cause? It is well known that plants (and indeed animals, as I could show by a series of facts) when placed out of their natural conditions, become, often from apparently slight and unintelligible causes, sterile. How many American plants fail in producing pollen in this country! the anthers of the Persian and Chinese Lilacs, as I observed this summer, are as destitute of good pollen as if they had been hybrids. Other plants produce good pollen, but are defective, as it appears, in their ovules, as their germen never swells. Linnæus² has remarked that most Alpine plants, when cultivated in the lowlands, are rendered quite sterile. In most of these cases, we see that sterility is compatable with long life and health. Is it, then, too bold a theory to suppose that all double flowers are first rendered by some change in their natural condition, to a certain degree, sterile; and that their vessels being charged with organizable matter in excess, (which would be greatly formed by high cultivation,) it is converted into petals—the organs which are nearest in their morphological nature and position to those whose functions are checked? Is there any shadow of truth in this theory, or is it an abortive one, as are the buds of the Gentiana?—C. Darwin. [We can only say that this is at least as reasonable an hypothesis as any that we have seen; but the greater frequency of double flowers in gardens where soil is rich, than in fields where it is poor, offers some difficulty in the way of Mr. Darwin's speculation.] P.S.—I also send a curious Cabbage-leaf, grown into the form of a perfect funnel, like the fold of paper into which grocers put sugar. It was borne on a long footstalk from the centre of an old stalk, from which a Cabbage had been cut this summer. I remember that De Candolle describes pitchers at the end of the leaves of some Cabbages, which he compares to those of the Nepenthes.³ Is this leaf something of the same kind? [Yes.]

¹ John Lindley (1799-1865), botanist, professor of Botany University College London 1829-1860. He was horticultural editor of the Gardeners' Chronicle from 1841. Darwin refers to Lindley 1840.

² Carl Linnaeus (1707-1778), Swedish botanist, physician, zoologist and taxonomist who introduced the binomial system of biological nomenclature.

³ Augustin Pyramus de Candolle (1778–1841), Swiss botanist. Darwin refers to Candolle 1839-40, 1: 272.