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Variation of Animals and Plants under Domestication, the — Volume 2 by Charles Darwin
page 107 of 776 (13%)
of V. lychnitis, naturally fertilised by its own pollen, gave from an AVERAGE
of twelve capsules ninety-six good seeds in each; whilst twenty flowers
fertilised with pollen from the yellow variety of this same species, gave as
the MAXIMUM only eighty-nine good seeds; so that we have the proportion of
1000 to 908, according to Gartner's usual scale. I should have thought it
possible that so small a difference in fertility might have been accounted for
by the evil effects of the necessary castration; but Gartner shows that the
white variety of V. lychnitis, when fertilised first by the white variety of
V. blattaria, and then by the yellow variety of this species, yielded seed in
the proportion of 622 to 438; and in both these cases castration was
performed. Now the sterility which results from the crossing of the
differently coloured varieties of the same species, is fully as great as that
which occurs in many cases when distinct species are crossed. Unfortunately
Gartner compared the results of the first unions alone, and not the sterility
of the two sets of hybrids produced from the white variety of V. lychnitis
when fertilised by the white and yellow varieties of V. blattaria, for it is
probable that they would have differed in this respect.

Mr. J. Scott has given me the results of a series of experiments on Verbascum,
made by him in the Botanic Gardens of Edinburgh. (16/17. The results have
since been published in 'Journ. Asiatic Soc. of Bengal' 1867 page 145.) He
repeated some of Gartner's experiments on distinct species, but obtained only
fluctuating results, some confirmatory, the greater number contradictory;
nevertheless these seem hardly sufficient to overthrow the conclusion arrived
at by Gartner from experiments tried on a larger scale. Mr. Scott also
experimented on the relative fertility of unions between similarly and
dissimilarly-coloured varieties of the same species. Thus he fertilised six
flowers of the yellow variety of V. lychnitis by its own pollen, and obtained
six capsules; and calling, for the sake of comparison, the average number of
good seed in each of their capsules one hundred, he found that this same
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