I have as yet spoken as if the varieties of the same species were
invariably fertile when intercrossed. But it is 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
kind with 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.
Pages:
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490