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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

between Rhod.
ponticum
Ponticum
and
catawbiense,
Catawbiense,
and that this hybrid "seeds as freely as it is possible to imagine." Had hybrids, when fairly treated,
always gone
gone
on decreasing in fertility in each successive generation, as Gärtner
believed
believes
to be the case, the fact would have been notorious to
nursery-men.
nurserymen.
Horticulturists raise large beds of the same
hybrid,
hybrids,
and such alone are fairly treated, for by insect agency the several individuals of the same hybrid variety are allowed to
cross freely
freely cross
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
Rhododendrons,
rhododendrons,
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
is,
is
if the genera of animals are as distinct from each
other
other,
as are the genera of plants, then we may infer that animals more widely
distinct
separated
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,
but,
but
as not one of these
nine species
nine species
breeds freely in confinement, we have no right to expect that the first crosses
be- tween
between
them and the canary, or that their hybrids, should be perfectly fertile. Again, with respect to the fertility in successive generations of the more fertile