| → though they rarely 1866 1869 1872 |
| generally 1859 1860 1861 |
|
| → external characters, yet generally differ in fertility 1866 1869 1872 |
| fertility 1859 1860 1861 |
|
| → fertility in the hybrid is 1859 1860 1861 1866 1869 |
| the fertility of a hybrid may be 1872 |
|
|
found that this difference of facility in making reciprocal crosses is extremely common in a lesser degree. He has observed it even between
closely related
Matthiola annua and glabra)
many botanists rank
only as varieties. It is also a remarkable fact, that hybrids raised from reciprocal crosses, though of course compounded of the very same two species, the one species having first been used as the father and then as the mother,
→though they rarely
differ in
→external characters, yet generally differ in fertility
in a small, and occasionally in a high degree. |
|
| Several other singular rules could be given from Gärtner: for instance, some species have a remarkable power of crossing with other species; other species of the same genus have a remarkable power of impressing their likeness on their hybrid offspring; but these two powers do not at all necessarily go together. There are certain hybrids
instead of having, as is usual, an intermediate character between their two parents, always closely resemble one of them; and such hybrids, though externally so like one of their pure parent-species, are with rare exceptions extremely sterile. So again amongst hybrids which are usually intermediate in structure between their parents, exceptional and abnormal individuals sometimes are born, which closely resemble one of their pure parents; and these hybrids are almost always utterly sterile, even when the other hybrids raised from seed from the same capsule have a considerable degree of fertility. These facts show how completely
→fertility in the hybrid is
independent of its external resemblance to either pure parent. |
|
| Considering the several rules now given, which govern the fertility of first crosses and of hybrids, we see that when forms, which must be considered as good and distinct species, are united, their fertility graduates from
|
