the longer the series of generations in which it has come true from
seed--the less the chance of reversion: for now, to be like the immediate
parents, is also to be like a long line of ancestry; and so all the
influences concerned--- that is, both parental and ancestral
heritability--act in one and the same direction. So, since the older a race
is the more reason it has to continue true, the presumption of the
unlimited permanence of old races is very strong.

Of course the race itself may give off new varieties; but that is no
interference with the vitality of the original stock. If some of the new
varieties supplant the old, that will not be because the unvaried stock is
worn out or decrepit with age, but because in wild Nature the newer forms
are better adapted to the surroundings, or, under man's care, better
adapted to his wants or fancies.

The second question, and one upon which the discussion about the wearing
out of varieties generally turns, is, Will varieties propagated from buds,
i.e., by division, grafts, bulbs, tubers, and the like, necessarily
deteriorate and die out? First, Do they die out as a matter of fact? Upon
this, the testimony has all along been conflicting. Andrew Knight was sure
that they do, and there could hardly be a more trustworthy witness.


"The fact," he says, fifty years ago, "that certain varieties of some
species of fruit which have been long cultivated cannot now be made to grow
in the same soils and under the same mode of management, which was a
century ago so perfectly successful, is placed beyond the reach of
controversy. Every experiment which seemed to afford the slightest prospect
of success was tried by myself and others to propagate the old varieties of
the apple and pear which formerly constituted the orchards of Herefordshire,