| → in most cases 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
| → and therefore we might expect that such variability 1859 1860 1861 1866 |
| which 1869 1872 |
|
| → be super-added to 1859 1861 |
| be superadded to 1860 1866 |
| be added to 1869 |
| would augment 1872 |
|
| → cross or in the first 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
| → their extreme variability in 1859 1860 1861 1866 |
| that in 1872 |
| OMIT 1869 |
|
| → on 1859 1860 1861 1866 |
| of one of 1869 1872 |
|
| → it is due to 1859 1860 1861 1866 |
| OMIT 1869 1872 |
|
| → being thus often rendered either impotent or at least incapable of 1859 1860 1861 1866 |
| fails under these circumstances to perform 1869 1872 |
|
| → identical with 1859 1860 1861 1866 |
| identical in all respects with 1869 |
| closely similar in all respects to 1872 |
|
| ↑ 1 blocks not present in 1859 1860 1861; present in 1866 1869 1872 |
| Moreover, Gärtner expressly states that hybrids from long-cultivated
plants are more subject to reversion than hybrids from species in their natural state; and this probably explains the singular difference in the results arrived at by different observers: thus, Max Wichura doubts whether hybrids ever revert to their parent- forms,
and he experimented on uncultivated species of willows; whilst Naudin, on the other hand, insists in the strongest terms on the almost universal tendency to reversion in hybrids, and he experimented chiefly on cultivated plants.
|
|
|
varieties), and this implies
→in most cases
that there has been recent
→and therefore we might expect that such variability
would often continue and
→be super-added to
that arising from the
act of crossing. The slight
of
in
the first
→cross or in the first
generation, in contrast with
→their extreme variability in
the succeeding generations, is a curious fact and deserves attention. For it bears on
the view which I have taken
→on
the
of ordinary
namely, that
→it is due to
the reproductive system
eminently sensitive to
conditions of life,
→being thus often rendered either impotent or at least incapable of
its proper function of producing offspring
→identical with
the parent-form. Now hybrids in the first generation are descended from species (excluding those
which have not had their reproductive systems in any way affected, and they are not variable; but hybrids themselves have their reproductive systems seriously affected, and their descendants are highly variable. |
|
| But to return to our comparison of mongrels and hybrids: Gärtner states that mongrels are more liable than hybrids to revert to either parent-form; but this, if it be true, is certainly only a difference in degree. ↑
Gärtner further
that when any two species, although most closely allied to each other, are crossed with a third species, the hybrids are widely different from each other;
if two very distinct varieties of one species are crossed with another species, the hybrids do not differ much. But this conclusion, as far as I can make out, is founded on a single experiment; and seems directly opposed to the results of several experiments made by Kölreuter. |
|
|
alone are the unimportant
which
|
