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Updated: May 22, 2025
Had hybrids, when fairly treated, always gone on decreasing in fertility in each successive generation, as Gartner believed to be the case, the fact would have been notorious to nurserymen.
Kolreuter makes the rule universal; but then he cuts the knot, for in ten cases in which he found two forms, considered by most authors as distinct species, quite fertile together, he unhesitatingly ranks them as varieties. Gartner, also, makes the rule equally universal; and he disputes the entire fertility of Kolreuter's ten cases.
Had hybrids, when fairly treated, gone on decreasing in fertility in each successive generation, as Gartner believes to be the case, the fact would have been notorious to nurserymen.
The following case is far more remarkable, and seems at first incredible; but it is the result of an astonishing number of experiments made during many years on nine species of Verbascum, by so good an observer and so hostile a witness as Gartner: namely, that the yellow and white varieties when crossed produce less seed than the similarly coloured varieties of the same species.
Even within the limits of the same genus, we meet with this same difference; for instance, the many species of Nicotiana have been more largely crossed than the species of almost any other genus; but Gärtner found that N. acuminata, which is not a particularly distinct species, obstinately failed to fertilise, or to be fertilised by, no less than eight other species of Nicotiana.
These plants differ considerably in appearance; they have a different flavour, and emit a different odour; they flower at slightly different periods; they grow in somewhat different stations; they ascend mountains to different heights; they have different geographical ranges; and lastly, according to very numerous experiments made during several years by that most careful observer Gärtner, they can be crossed only with much difficulty.
The harmlessness of abstinence was affirmed by Kräpelin, Cramer, Gärtner, Tuczek, Schottelius, Gaffky, Finkler, Selenew, Lassar, Seifert, Gruber; the last, however, added that he knew very few abstinent young men, and himself only considered abstinence good before full development, and intercourse not dangerous in moderation even before then.
As Gartner found that there was sometimes an innate difference in different INDIVIDUALS of the same two species in crossing; so Sagaret believes this to be the case with different individuals of the same two species in being grafted together.
Even within the limits of the same genus, we meet with this same difference; for instance, the many species of Nicotiana have been more largely crossed than the species of almost any other genus; but Gartner found that N. acuminata, which is not a particularly distinct species, obstinately failed to fertilise, or to be fertilised by, no less than eight other species of Nicotiana.
Gärtner, whose strong wish was to draw a marked line of distinction between species and varieties, could find very few and, as it seems to me, quite unimportant differences between the so-called hybrid offspring of species, and the so-called mongrel offspring of varieties. And, on the other hand, they agree most closely in very many important respects.
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