But it seems to me impossible to
resist the evidence of the existence of a certain amount of sterility
in the few following cases, which I will briefly abstract. The
evidence is at least as good as that from which we believe in the
sterility of a multitude of species. The evidence is, also, derived
from hostile witnesses, who in all other cases consider fertility and
sterility as safe criterions of specific distinction. Gartner kept
during several years a dwarf kind of maize with yellow seeds, and a
tall variety with red seeds, growing near each other in his garden;
and although these plants have separated sexes, they never naturally
crossed. He then fertilised thirteen flowers of the one with the
pollen of the other; but only a single head produced any seed, and
this one head produced only five grains. Manipulation in this case
could not have been injurious, as the plants have separated sexes. No
one, I believe, has suspected that these varieties of maize are
distinct species; and it is important to notice that the hybrid plants
thus raised were themselves PERFECTLY fertile; so that even Gartner
did not venture to consider the two varieties as specifically
distinct.
Girou de Buzareingues crossed three varieties of gourd, which like the
maize has separated sexes, and he asserts that their mutual
fertilisation is by so much the less easy as their differences are
greater. How far these experiments may be trusted, I know not; but the
forms experimentised on, are ranked by Sagaret, who mainly founds his
classification by the test of infertility, as varieties.
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