That these are constantly appearing, is a matter of common observation;
but the manner of their production has given rise to much diversity of
opinion. The theory that they are the results of replanting, from the
seeds of successive generations of the same tree, is called the Van
Mons' theory, after Dr. Van Mons, of Belgium, who devoted many years of
close study and application to the improvement of fruit, especially of
pears, by this method. His directions may be briefly summed up as
follows. Plant seeds from any good variety of fruit; let those seedlings
stand without grafting, until they bear. Take the first fruit from the
best of those seedlings, and plant it and produce other seedlings, and
so on. The peach and plum are said to reach a high state of excellence
in the third generation, while the pear requires the fifth. Seeds from
old trees are said to have a great tendency to return to their wild
origin, while those of young, improving trees will more generally
produce a better fruit. The seeds from a graft from a young tree does
not produce a better than itself. The succession must be of seedlings.
This theory requires long practice, and is exposed to interruptions by
the crosses that will necessarily occur between different trees in
blossom. And we have in so many cases had a fruit of great perfection
arise from a single planting of seed from some known variety, that we
must conclude the improvement to be produced by some other principle
than that of the Van Mons' theory. The evidence is in favor of the
opinion that new varieties of fruit arise from cross-fertilization in
the blossoms of different kinds, and that the improvement of the
qualities of any given variety is the result of cultivation. Some of the
best plums we have are known to have been the product of fertilizing the
blossoms of one tree from the pollen of another; this is constantly
taking place with our fruits, and is consequent upon our mixed orchards.
Let this be attended to artificially, by covering branches with gauze,
to prevent the fertilization by bees and winds, and make the cross
between any two varieties you choose, and the results may prove highly
beneficial. The amateur cultivator may render essential service to
pomology by this practice. We know that all our choice fruits have come
from those not fit for use. It is not improved cultivation of the old,
barely, but the production of new varieties. The subject of further
improvement, therefore, demands careful study and practice. The seeds of
established varieties, planted at once without drying, will often
reproduce the same. We are not certain but they generally would, if not
affected by blossoms of contiguous trees.