Because, as yet, no certain rules can be laid down for the production
of a given result by crossing flower on flower, it does not follow
that there are not certain invariable principles which govern the
process. It is but a little while since breeding animals had any
pretension to scientific rules. But, by careful practice and
observation, the most important improvement has been attained in all
the animals belonging to the farm. And if careful research and
experiment do not result in absolute certainty, they will yet render
the production of fine varieties of fruit, by the crossing of the old
ones, a matter of much less chance than it now is.
The art of cross-fertilization is being much more practised by
florists than by pomologists, and for obvious reasons. What the
breeder of annuals can do in a few months requires more than as many
years from him that essays to raise new fruits. Many florists’
flowers, however, require as long and even a longer time than apples
or pears; and it is a marvel that the phlegmatic patience of the
tulip-loving Dutch Jobs should not have found imitators in the
orchard. If a man can wait ten years to ascertain that all his
seedling bulbs are good for nothing, or at the best, that out of ten
thousand, but one or two are worth keeping, surely the patience of an
enthusiast in fruit ought not to snap by being drawn through such a
space.
Two methods for originating new varieties of fruit have been
practised; the _natural_ method of Van Mons, and the _artificial_
method of Knight. Van Mons, born at Brussels in 1765, was a man of
fine genius and thorough education. Although he is chiefly known as a
pomologist, his labors in the nursery were only incidental to the
regular occupation of a public scientific life. M. Poiteau quaintly
says of him that he writes “on the gravest subjects, in the midst of
noise, in a company of persons who talk loudly on frivolous subjects,
and takes part in the conversation without stopping his pen.”
Van Mons’ theory is founded upon two physical facts:
1. _That all seeds in a state of nature can be made by cultivation to
vary from their condition, which variations may be fixed, and become
permanent._
2. _That all cultivated seeds have a tendency to return toward that
natural state from which they originally varied._ We say _toward_, for
he supposed that an improved fruit would never return absolutely to
the original and natural type.
It was upon this last principle that Van Mons accounted for the fact,
that as a general thing, the seeds of fine old varieties of fruit
produced only inferior kinds. Recourse could not be had therefore to
seeds of improved fruit.
On the other hand, the seed of fruits absolutely wild would produce
fruits exactly like their original. If the seed of the wild pear be
gotten from the wood and planted in a garden, every seed will yield
only the wild pear again. But if a wild pear be transplanted, and put
under new influences of soil, climate and cultivation, its fruit will
begin to augment and improve. The change is not merely upon the size
and appearance of the fruit, it affects also the qualities of the
_seed_. For if the seed be now planted, the difference between a wild
pear, _in a state of nature_ and the same wild pear-tree _in a state
of cultivation_ will at once appear in this, that whereas the seed of
the first is _constant_, the seed of the second shows an inclination
to _vary_. Here then is a starting. When once the habit of _variation_
is gained, the foundation of improvement is laid. In a short time the
enthusiasm of Van Mons had collected into his garden 80,000 trees upon
which he was experimenting, nor can the result of his labors be better
stated than in the words of M. Poiteau:
“That so long as plants remain in their natural situation,
they do not sensibly vary, and their seeds always produce
the same; but on changing their climate and territory
several among them vary, some more and others less, and when
they have once departed from their natural state, they never
again return to it, but are removed more and more therefrom,
by successive generations, and produce, sufficiently often,
distinct races, more or less durable, and that finally if
these variations are even carried back to the territory of
their ancestors, they will neither represent the character
of their parents, or ever return to the species from whence
they sprung.”
Accordingly, Van Mons began to sow the seeds of natural and wild fruit
which were in a _variable_ state. By all means within his power he
hastened his seedlings to show fruit. The first generation showed only
poor fruit but decidedly better than the wild. Selecting the seed of
the best of these, he sowed again. From the fruit of these he sowed
the third generation. From the third, a fourth; and from the fourth, a
fifth; as far as the eighth generation.
His experience showed that there was great difference among different
species of fruit in the number of generations through which they must
pass before they were perfect. The apple yielded good fruit in the
fourth generation. Stone fruits produced perfect kinds in the third
generation. Some varieties afforded perfect fruit in the fifth
generation, while others go on improving to the eighth.
The time required for this renovation diminished at each remove from
the normal or wild state. Thus, the trees from the second sowing of
the pear-seed fruited in from ten to twelve years; those from their
seed, or of the third genetion in from eight to ten years; those of
the fourth generation in from six to eight years; those of the fifth
generation, in six years, and those in the eight, in four years. These
are the _mean_ terms of all his experiments.
To obtain perfect stone fruits, through four successive generations,
from parent to son, required from twelve to fifteen years; the apple
required twenty years, and the pear, when carried only to the fifth
generation, required from thirty to thirty-six years.
HYBRIDIZATION, OR KNIGHT’S METHOD.—Andrew Knight, one of the most
original and philosophic horticulturists that ever lived, pursued an
entirely different method—that of _cross-fertilization_. He carefully
removed the anthers from the blossoms upon which he wished to operate,
so that the stigma should not receive a particle of the pollen
belonging to its own flower. He then procured from the variety which
he wished to cross, a portion of the pollen, and artificially
impregnated the prepared blossom with it. When the fruit thus produced
had ripened its seeds, they were sown, and by regular process brought
into bearing. The progeny were found to combine, in various degrees of
excellence, the qualities of both parents.