Paxton's Magazine of Botany 16: 13-14 (1849)
By M. D. Beaton, Gardener at Shrubland Park
The practical application of hybridizing, or cross-breeding, has not kept pace with the progress of improved cultivation, for the last dozen or fifteen years—although the scientific bearing of the subject has been fully explained, and widely circulated during that time. It is true, great attention has of late years been bestowed on the improvement of a few popular genera, which has produced very marked results. But to obtain a surer insight into the mysterious process of cross-breeding, we must push our experiments much further. The power of modifying certain peculiarities in plants, which refuse to yield to the ordinary process of the hybridizer, is not at present sufficiently known to enable us to lay down rules for practice. Yet from some experiments in this direction, I am led to believe that many plants now thought to be sterile, and incapable of interbreeding with others, may be so managed by a previous course of culture, as to make them yield seed.
The late Dean of Manchester—who may be said to be the father of scientific hybridizing—recently experimented more for the sake of proving the affinities of certain families of plants, than with a view to the production of improved races. Some years ago, there were a few lingering hopes entertained, that superfoetation was possible among plants, and in 1837, I suggested in the "Gardeners' Magazine," a simple experiment to prove this to be true, and which might likewise be of some service in cases of cross-breeding. It was to place pollen on one division only of a divided stigma, to see what effect it had on all the ovules in the germen. If it was found to fertilise all the ovules, then to apply different pollen to each division of a stigma, and thus induce superfoetation. Mr. Herbert took up this point with the ardour of youth—he soon ascertained that pollen placed on one division of a stigma, fertilised all the ovules in the germen, but he could not make two grains of different pollen act on an ovule at the same time, as he tells us in his last paper on this subject in the second volume of "The Journal of the Horticultural Society of London."
Some years since it was firmly believed, that the seedlings from a crossed flower could be altered in their constitution, or at least enlarged in their flowers, by a particular mode of managing the mother-plant while the seeds were in progress towards maturity, and this belief is still entertained by some cultivators, but is not founded on facts. When Mr. Herbert's "Treatise on Cross-Breeding" appeared in 1837, some countenance was given in it to this doctrine in the case of certain seedling Camellias, which were raised from single ones, and by a peculiar way of treating the mother-plant while these seeds were in progress, it was supposed to have induced the flowers to become double. From this I dissented at once (see "Gardeners' Magazine," xiii. 276) and declared that I could not perceive how any mode of management, could affect the offspring subsequent to the impregnation. This led to a correspondence and personal intercourse, which Mr. Herbert in the most kind and affable manner, allowed to go on for the last ten years of his useful life. He expressed an anxious desire that the point in doubt should be cleared up by a rigid course of experiments. This was in 1838, but although trials had then commenced, it was the end of 1845 before a final judgment was passed in my favour. Now, seeing that I am the party left to make the assertion, I do not wish any one to believe the result, but rather experiment for himself. Calceolaria, Fuchsia, or Pelargonium, will answer to make trials with, as being very easy to operate upon, and giving proofs in the second season. It is only necessary to be most scrupulous about the access of any pollen but the sort intended, and not to use a camel-hair brush to dust the pollen with. A brush that has been used more than once is little better than a lottery chance for experiments.
Take two plants of the kind you fix upon—subject one of them to the worst treatment you can devise, after you dust the stigma, and the other just the contrary—in short any sort of treatment with its opposite will answer. I may, however, state the most severe trial that was made in the case referred to. Two scarlet Pelargoniums of one kind were planted out in rich compost under a south wall—the first two crops of flowers were cut off to give time for the roots to extend more freely. Then two of the strongest trusses of bloom on each were selected for the experiment, and all the rest were cut off, and also the shoots were stopped. A dozen blossoms on each shoot were impregnated with the same kind of pollen, and in a few days when it was ascertained that the pollen took effect—a truss from each plant was cut off with the whole length of the footstalks—these were put in a glass with damp sand under a hand-glass in the stove, where seven seeds ripened, the rest having died through this hard treatment. The two plants, with the other two trusses were petted as only experimentalists can understand. The produce of the whole is now three years old, and there is not the slightest variation perceptible among them yet.
I believe, however, that sterility may be overcome in part, and some opposite characters may be stamped on seedlings, by peculiar treatment to the mother-plant previous to impregnation.