In this case it is called "fixing," as gardeners
generally believe that through selection the varieties are brought to
the required degree of purity. This belief seems to rest mainly on
observations made in practice, where, as we have seen, isolation is of
very rare application. Most varieties would no doubt be absolutely pure
from the first moment of their existence, if it were only possible to
have them purely fertilized. But in practice this is seldom to be
obtained. Ordinarily the breeder is content with such slow [198]
improvement as may be obtained with a minimum of cost, and this mostly
implies a culture in the same part of the nursery with older varieties
of the same species. Three, four or five years are required to purify
the novelty, and as this same length of time is also required to produce
sufficient quantities of seed for commercial purposes, there is no
strong desire to shorten the period of selection and fixation. I had
occasion to see this process going on with sundry novelties at Erfurt in
Germany. Among them a chamois-colored variety of the common stock, a
bluish _Clarkia elegans_ and a curiously colored opium-poppy may be
mentioned. In some cases the crossfertilization is so overwhelming, that
in the next generation the novelty seems entirely to have disappeared.
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