It
is well known that if pollen of a distinct species be placed on the stigma
of a flower, and its own pollen be afterwards, even after a considerable
interval of time, placed on the same stigma, its action is so strongly
prepotent that it generally annihilates the effect of the foreign pollen;
so it is with the pollen of the several forms of the same species, for
legitimate pollen is strongly prepotent over illegitimate pollen, when both
are placed on the same stigma. I ascertained this by fertilising several
flowers, first illegitimately, and twenty-four hours afterwards
legitimately, with pollen taken from a peculiarly coloured variety, and all
the seedlings were similarly coloured; this shows that the legitimate
pollen, though applied twenty-four hours subsequently, had wholly destroyed
or prevented the action of the previously applied illegitimate pollen.
Again, as in making reciprocal crosses between the same two species, there
is occasionally a great difference in the result, so the same thing occurs
with trimorphic plants; for instance, the mid-styled form of Lythrum
salicaria was illegitimately fertilised with the greatest ease by pollen
from the longer stamens of the short-styled form, and yielded many seeds;
but the latter form did not yield a single seed when fertilised by the
longer stamens of the mid-styled form.
In all these respects, and in others which might be added, the forms of the
same undoubted species, when illegitimately united, behave in exactly the
same manner as do two distinct species when crossed.
Pages:
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482