Charles Darwin's natural selection : being the second part of his big species book written from 1856 to 1858 / edited from the manuscript by R.C. Stauffer.

  • Darwin, Charles, 1809-1882.
Date:
[1975]
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Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Charles Darwin's natural selection : being the second part of his big species book written from 1856 to 1858 / edited from the manuscript by R.C. Stauffer. Source: Wellcome Collection.

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    POSSIBILITY OF ALL ORGANIC BEINGS CROSSING [Hippeastrums, of complicated origin, descended from several species, he found that almost every flower touched with pollen from another cross produced seed abundantly, and those which were touched with their own pollen either failed entirely, or formed slowly a pod of inferior size, with fewer seeds. In the 'Horti¬ cultural Journal' he adds that, the admission of the pollen of another cross-bred Hippeastrum (however complicated the cross) to any one flower of the number, is almost sure to check the fructification of the others. In a letter written to me in 1839, Dr. Herbert says that he had already tried these experiments during five consecutive years, and he subsequently repeated them, with the same invariable result. He was thus led to make an analogous trial on a pure species, namely, on the Hippeastrum aulicum, which he had lately imported from Brazil: this bulb produced four flowers, three of which were fertilised by their own pollen, and the fourth by the pollen of a triple cross between H. bulbulosum, reginae, and vittatum; the result was, that the ovaries of the three first flowers soon ceased to grow, and after a few days perished entirely: whereas the pod impregnated by the hybrid made vigorous and rapid progress to maturity, and bore good seed, which vegetated freely. This is, indeed, as Herbert remarks, a strange truth, but not so strange as it then appeared.] 9A/N0W considering how many crossed Hippeastrums were experimentised on, & that they were crossed in all sorts of ways, & that the pollen in each case applied to the stigma of one plant was from some other hybrid, & therefore not sound, I can under¬ stand the strong &/10/overpowering (marked) good effect of its application, only on the abstract good from crossing, as seen in crossing varieties. Moreover this case of the hybrid Hippeastrums is confirmed as we shall hereafter see in the chapter on Hybridism in some degree by some extraordinary cases, well ascertained by Gaertner, Kolreuter, & Herbert, in which pure species of Lobelia, Passiflora, Hippeastrum, Verbascum, had both pollen & germ in proper condition as shown by their fertilising, & being fertilised by, other species, but yet were incapable of, self-fertilisation, when their own pollen was placed on their own stigmas. These facts seem to show that in hybrids from distinct species, independently of the greater vigour & luxuriance often acquired, that even in regard to fertility, which is undoubtedly almost universally diminished or quite annihilated, there is some slight counter¬ balancing good in the act of crossing which occasionally appears in the intercrossing of hybrid with hybrid./ 40