| → pollen 1866 |
| varietys own pollen 1869 |
|
| → prepotency of this kind always accompanies the sterility which follows from crossing distinct 1866 |
| with species which are mutually sterile, the pollen of each is always prepotent on its own stigma over that of the other 1869 |
|
| → sterility, or 1866 |
| the mutual sterility, or the 1869 |
|
| → we may infer that, 1866 |
| OMIT 1869 |
|
| → should 1866 |
| crossed species should 1869 |
|
| → profited by 1866 |
| received any advantage from 1869 |
|
|
character. And the more prepotent the
→pollen
could be rendered through natural
the greater the advantage would be. We know from the researches of Gärtner
→prepotency of this kind always accompanies the sterility which follows from crossing distinct
but we do not know whether
is a consequence of
→sterility, or
sterility a consequence of
If the latter view be correct,
→we may infer that,
as the prepotency became stronger through natural selection, from being advantageous to a species in process of formation, so the sterility consequent on prepotency would at the same time be augmented; and the final result would be various degrees of sterility, such as
with
existing
This
view might be extended to
if the female before each birth received several males, so that the sexual element of the prepotent male of her own variety obliterated
effects
the access of previous males
other
but we have no reason to believe, at least with terrestrial animals, that this is the case; as most males and females pair for each birth, and some few for life. |
|
| On the whole we may conclude that with animals the sterility of crossed species has not been slowly
through natural selection; and as this sterility follows the same general laws in the vegetable as in the animal kingdom, it is improbable, though apparently possible, that
plants
→should
have been rendered sterile by a different
From this consideration, and remembering that species which have never co-existed in the same country, and which therefore could not have
→profited by
having been rendered mutually infertile, yet are
|
