They indicate the size of the cultures required to get all the
possible combinations, and show that in ordinary cases many thousands of
individuals have to be cultivated, in order to exhaust the whole range
of possibilities. They further show that among all these thousands, only
very few are constant in all their characters; in fact, it may easily be
seen that with seven differentiating points among the 16,384 named
above, only one individual will have all the seven qualities in pure
active, and only one will have them all in a purely dormant condition.
Then there will be some with some attributes active and others latent,
but their numbers will also be very small. All others will split up in
the succeeding generation in regard to one or more of their apparently
active marks. And since only in very rare cases the stable hybrids can
be distinguished by external characters from the unstable ones, the
stability of each individual bearing a desired combination of characters
would have to be established by experiment [306] after pure
fertilization. Mendel's law teaches us to predict the difficulties, but
hardly shows any way to avoid them. It lays great stress on the old
prescript of isolation and pure fertilization, but it will have to be
worked out and applied to a large number of practical cases before it
will gain a preeminent influence in horticultural practice.
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