if the parent pear or apple tree has been cut down or
headed, and scions are then, taken from the young shoots of the stem,
and ingrafted; I believe those grafted trees will continue to grow for
ten or twelve years, before they bear fruit, almost as long as
seedling trees, that is they will require as much time, as those new
shoots from the lopped trunk would require, before they produce fruit.
It should thence be inquired, when grafted fruit trees are purchased,
whether the scions were taken from bearing branches, or from the young
shoots of a lopped trunk; as the latter, I believe, are generally
sold, as they appear stronger plants. This greater similitude of the
progeny to the parent in solitary reproduction must certainly make
them more liable to hereditary diseases, if such have been acquired by
the parent from unfriendly climate or bad nourishment, or accidental
injury.

In respect to the sexual progeny of vegetables it has long been
thought, that a change of seed or of situation is in process of time
necessary to prevent their degeneracy; but it is now believed, that it
is only changing for seed of a superior quality, that will better the
product. At the same time it may be probably useful occasionally to
intermix seeds from different situations together; as the anther-dust
is liable to pass from one plant to another in its vicinity; and by
these means the new seeds or plants may be amended, like the marriages
of animals into different families.

As the sexual progeny of vegetables are thus less liable to hereditary
diseases than the solitary progenies; so it is reasonable to conclude,
that the sexual progenies of animals may be less liable to hereditary
diseases, if the marriages are into different families, than if into
the same family; this has long been supposed to be true, by those who
breed animals for sale; since if the male and female be of different
temperaments, as these are extremes of the animal system, they may
counteract each other; and certainly where both parents are of
families, which are afflicted with the same hereditary disease, it is
more likely to descend to their posterity.

The hereditary diseases of this country have many of them been the
consequence of drinking much fermented or spirituous liquor; as the
gout always, most kinds of dropsy, and, I believe, epilepsy, and
insanity. But another material, which is liable to produce diseases in
its immoderate use, I believe to be common sal