| → of the same hybrid variety 1859 1860 1861 1866 1869 |
| OMIT 1872 |
|
| → more easily crossed 1859 1860 1861 1866 1869 |
| crossed more easily 1872 |
|
| → other 1859 1860 1861 1866 1869 |
| distinct species of 1872 |
|
|
are perfectly fertile. Mr. C. Noble, for instance, informs me that he raises stocks for grafting from a hybrid between Rhod.
and
and that this hybrid "seeds as freely as it is possible to imagine." Had hybrids, when fairly treated,
on decreasing in fertility in each successive generation, as Gärtner
to be the case, the fact would have been notorious to
Horticulturists raise large beds of the same
and such alone are fairly treated, for by insect agency the several individuals
→of the same hybrid variety
are allowed to
with each other, and the injurious influence of close interbreeding is thus prevented. Any one may readily convince himself of the efficiency of insect-agency by examining the flowers of the more sterile kinds of hybrid
which produce no pollen, for he will find on their stigmas plenty of pollen brought from other flowers. |
|
| In regard to animals, much fewer experiments have been carefully tried than with plants. If our systematic arrangements can be trusted, that
if the genera of animals are as distinct from each
as are the genera of plants, then we may infer that animals more widely
in the scale of nature can be
→more easily crossed
than in the case of plants; but the hybrids themselves are, I think, more sterile. I doubt whether any case of a perfectly fertile hybrid animal can be considered as thoroughly well authenticated. It should, however, be borne in mind that, owing to few animals breeding freely under confinement, few experiments have been fairly tried: for instance, the canary-bird has been crossed with nine
→other
finches,
as not one of these
breeds freely in confinement, we have no right to expect that the first crosses
them and the canary, or that their hybrids,
|
