" Mr. Herbert tried similar experiments
during many years, and always with the same result. These cases serve to
show on what slight and mysterious causes the lesser or greater fertility
of a species sometimes depends.
The practical experiments of horticulturists, though not made with
scientific precision, deserve some notice. It is notorious in how
complicated a manner the species of Pelargonium, Fuchsia, Calceolaria,
Petunia, Rhododendron, etc., have been crossed, yet many of these hybrids
seed freely. For instance, Herbert asserts that a hybrid from Calceolaria
integrifolia and plantaginea, species most widely dissimilar in general
habit, "reproduces itself as perfectly as if it had been a natural species
from the mountains of Chile." I have taken some pains to ascertain the
degree of fertility of some of the complex crosses of Rhododendrons, and I
am assured that many of them are perfectly fertile. Mr. C. Noble, for
instance, informs me that he raises stocks for grafting from a hybrid
between Rhod. ponticum and catawbiense, and that this hybrid "seeds as
freely as it is possible to imagine." Had hybrids, when fairly treated,
always gone on decreasing in fertility in each successive generation, as
Gartner believed to be the case, the fact would have been notorious to
nurserymen. Horticulturists raise large beds of the same hybrid, and such
alone are fairly treated, for by insect agency the several individuals are
allowed to cross freely with each other, and the injurious influence of
close interbreeding is thus prevented.
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