s favourable, so I have found it with illegitimate unions. 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 {182} 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 something analogous
occurs with dimorphic plants; for a short-styled cowslip (_P. veris_)
yields more seed when fertilised by the long-styled form, and less seed
when fertilised by its own form, compared with a long-styled cowslip when
fertilised in the two corresponding methods.

In all these respects the forms of the same undoubted species, when
illegitimately united, behave in exactly the same manner as do two distinct
species when crossed. This led me carefully to observe during four years
many seedlings, raised from several illegitimate unions. The chief result
is that these illegitimate plants, as they may be called, are not fully
fertile. It is possible to raise from dimorphic species, both long-styled
and short-styled illegitimate plants, and from trimorphic plants all three
illegitimate forms. These can then be properly united in a legitimate
manner. When this is done, there is no apparent reason why they should not
yield as many seeds as did their parents when legitimately fertilised. But
such is not the case; they are all infertile, but in various degrees; some
being so utterly and incurably sterile that they did not yield during four
seasons a single seed or even seed-capsule. These illegitimate plants,
which are so sterile, although united with each other in a legitimate
manner, may be strictly compared with hybrids when crossed _inter se_, and
it is well known h