We may limit ourselves in the first place to the seeds of the unobserved
hybrids. For the greater part they will repeat the character of their
parents and still remain concealed. But a small number will display the
varietal marks, as for example showing white flowers in a field of blue
ones. Hence, the indirect consequence of the spontaneous crosses will be
the same in the species, as was the direct effect in the variety, only
that it appears a year later. It will then be eliminated in the process
of selection.
Obviously, this elimination conduces only to a partial purification. The
conspicuous plants will be destroyed, but a greater number of hybrids
will remain, still concealed by their resemblance to the general type
and will be spared to repeat the same process next year. So while the
variety may be freed every year from the impurities brought into it in
the preceeding summer, the admixtures of the species [212] will continue
during a number of years, and it may not be possible to get rid of them
at all.
It is an often recurring assertion that white varieties of colored
species are the most stable of all horticultural races. They are often
said to be at least as constant as the species itself, and even to
surpass it in this quality. With our present state of knowledge, the
explanation of this general experience is easily given.
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