On some facts connected with Hybridism.
In a letter to A. Murray, Esq., by I. Anderson-Henry, Esq.
You will remember my writing to you a letter of December 24, 1870, which was afterwards printed under the heading of "Hybridism v. Mimicry" in the ‘Gardeners' Chronicle’ of January 7, 1871, p. 10; and if you think what I have now to communicate deserving of being submitted to the Scientific Committee, or of being published, I must beg special reference to that communication.
You will remember that it was written by me as confirmatory of a remark by you, in a leading article of the 'Gardeners' Chronicle' (1870, p. 1639), that "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." And I observed how remarkably that observation was illustrated, not after the second generation, but in the first generation from the hybrid; and I referred you to Darwin's then recent publication of 'Animals and Plants,' vol. i. p. 400, where he did me the honour to cite two experiments of mine, with only one of which I have now to trouble you: he there says, "Mr. Henry fertilized Arabis blepharophylla with pollen of A. Soyeri; and the pods thus produced, of which he was so kind as to 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, as I then went on to observe, Mr. Darwin had there most singularly anticipated the very result I had then to communicate, when he added:—"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 bean analogous fact." Mr. Darwin alluded to the large size of the pods of the above Arabis crop, and of a Rhododendron, which I had communicated to him.
But I must still so far recapitulate. I had just two seed-pods of the above crop (Arabis blepharophylla x A. Soyeri), both of which were one-half larger than the natural seed-pods of A. blepharophylla, the seed-bearer. Though so large, there was only one ripe seed in one pod and seven in the other, of which only four were sound. I had three or four plants only from both. One was a perfect monster. Unlike either parent, the height of the flower-stem being from 3 to 4 inches in the one parent, and not above 6 inches in the other, it sent up a flower-spike 18 inches high, bearing flowers (followed by seed-pods) for more than half its length on the upper portion of the stem—a thing wholly different from either of the species from which it sprung.
Desirous to find how the progeny of such a monstrous form would behave, I saved the seeds, which were very abundant. They vegetated most freely; and the plants are now for the most part in bloom or offering to flower.
That you may judge how far they have departed in this (the second) generation from the original types, I beg to send herewith:—
I have lost A. blepharophylla, the original seed-bearing species (a not over-hardy plant). But if you will please to turn up Torrey and Gray's 'Flora of North America,' at p. 667 you will find it is described as having a stem of only 3-4 inches, with purple-coloured flowers.
Now to you, so much better able than I am to detect in detail all the particulars in which these seedlings in the second generation have departed from the original types, I need only further observe that while the flowers have dwindled to below half the size, they have increased tenfold in number over those of either parent. The leaves, too, seem wholly altered in character; and the rosy tint of the flowers of the original seed-bearer (A. blepharophylla), very faint in the first, is entirely lost in the pure white of the second generation.
In a word, in length of stem, habit of flowering, colour of flowers, and form of leaves, these plants of the second generation might, I venture to assert, be passed by any botanist as a new species, and fully verify what Darwin and you have enunciated as above noticed.
If you think it worthy, would you kindly submit this communication to the Scientific Committee, with the accompanying specimens, at their first meeting.
I have, I find, given the particulars so fully of the first crop as to save the necessity of your referring to my letter of December 24, 1870.
I shall be enabled some time during the summer, I expect, to communicate further results of crossing Begonias, having some of the lobes of the stigmas of the female flowers first removed. I communicated one instance of such a crop last year, where the seedling had wholly departed from the dioecious condition of the parents, and gone into the monoecious state.—I. ANDERSON-HENRY.
May 12.—On looking over a bed of the same second generation of hybrid seedlings this morning, which I had planted apart from the others, I find many of them (forward to flower) of various habits and sizes, one of which, the smallest, I now enclose, No. 4. This tiny thing, not 2 inches in height, has, you will observe, 6 flower-stalks, with large umbels (large for the plant) of flowers at the top, and some having flowers at the axils. All the brood strongly illustrate your doctrine of variation, as not one of them offers a return to either parent, and the excessive tendency to flower is most noteworthy in them all.