Chronicle 31: 10 (Jan. 7, 1871)
Hybridism v. Mimicry
Mr. Murray's article in the Gardeners' Chronicle (1870, p. 1639) touches on several points of much interest to me. He says, "after the second generation of hybrids, those which do not revert to the type break out into an overflow of irregular variation, which supplies many of his most remarkable sports to the horticulturist." I have a most remarkable illustration of the truth of the above remark, not after the second generation, but in the first generation of the hybrid. If you will be so good as turn to "Darwin's Animals and Plants," vol. 1., p. 400, you will find he does me the honour to cite two experiments of mine, the first of which related to the unnaturally large size of the seed-pods produced on Rhododendron Dalhousiae by crossing it with Rhododendron Nuttallii, when he observes, "We see here the effect of foreign pollen apparently confined to increasing the size of the ovarium; but (he adds) we must be cautious in assuming, as the following case shows, that in this instance size has been directly transferred from the male parent to the capsule of the female plant. Mr. Henry fertilised Arabis blepharophylla with pollen of A. Soyeri, and the pods thus produced, of which he was so kind as send me detailed measurements and sketches, were much larger in all their dimensions than those naturally produced by either of the male or female parent species." And, singularly enough, Mr. Darwin in his brief summary of these and kindred experiments, anticipates or forecasts the result I am now to communicate, when he adds:— "In a future chapter we shall see that the organs of vegetation in hybrid plants, independently of the character of either parent, are sometimes developed to a monstrous size, and the increased size of the pods in the foregoing cases may be an analogous fact." I may observe that there were just two seed pods of this latter cross (Arabis blepharophylla x A. Soyeri), both of which were one half larger than the natural pods of the latter, or seed-bearer. I may also observe that of the first, sown on June 27, 1867, only one seed was ripe, and of the second, sown on July 4 of the same year, there were seven seeds, of which only four were sound. The first pod, I find noted, had been pulled before it was fully ripe, and only one seed was perfect. I had three or four plants only from both. These bloomed this bygone summer. One was a perfect monster. Unlike either parent, in having an umbel or a flower-stem of about 3 or 4 inches high in one of the parents, and not above 6 inches in the other, it sent up a flower-spike (now before me) 18 inches high, bearing flowers, as it now has seed-pods, for more than half that height upon the stem—a thing wholly different from either of the species from which it sprung. I may here notice a no less extraordinary departure from the normal condition which occurred to me in a Draba, a hybrid immediately from the crossed seed. I had received from the Rev. Mr. Ellacombe, of Bitton, a tiny Draba, named D. incarnata, of whose origin I know nothing, but it seems to be a species—and very like a Greenland one. I had got from imported seed an Andean Draba, a suffruticose species, by the name of D. violacea, and though from 14,000 feet above the sea, it was impatient of our climate. Desirous to incorporate its lovely tint of purple with the white flowers of D. incarnata, I crossed it on the latter. From the seeds (three or four at most) I raised only two plants. These two, though looking a little more robust, were a reproduction of the mother in every feature; but last summer one sent up a flower-spike triple the thickness of that of the female parent, which also flowered, and nearly four times its height, being 14 1/2 inches in the hybrid, and only 4 inches in the female parent. The second also flowered with a stem 9 inches high. Except in being a little more robust, and so much taller in stem, both hybrids were in every feature the mother, even to the colour of the blooms, being of an ashy white colour. I take these particulars from my note-book, as I have done in the case of the Arabis, both belonging to the same natural order; and I beg to repeat that in the one case, as in the other, I took the utmost care to prevent the possibility of failure. I should have mentioned that the D. violacea is a much taller species, attaining to about 18 inches in its full-grown condition. An account and figure of it is given by Sir "W. J. Hooker in the "Icones Plantarum," and it is figured and described by Dr. Hooker in the "Botanical Magazine."