The _Iris kaempferi_, a large-flowered Japanese
species much cultivated in gardens, is very variable in the number of
the different parts of its flowers, and may in some instances be seen
even with six stamens. If studied in the same way as Heinricher's iris,
it no doubt will yield highly interesting and confirmatory results.
Many other instances of such systematic atavism could be given, and
every botanist can easily add some from memory. Many anomalies,
occurring spontaneously, are evidently due to the same principle, but it
would take too long to describe them.
Reversion may occur either by buds or by seeds. It is highly probable
that it occurs more readily by sexual than by asexual propagation. But
if we restrict the discussion to the limits [175] hitherto observed,
seed-reversions must be said to be extremely rare. Or rather cases which
are sufficiently certain to be relied upon, are very rare, and perhaps
wholly lacking. Most of the instances, recorded by various writers, are
open to question. Doubts exist as to the purity of the seeds and the
possibility of some unobserved cross disturbing the results.
In the next lecture we shall deal in general with the ordinary causes
and results of such crosses. We shall then see that they are so common
and occur so regularly under ordinary circumstances that we can never
rely on the absolute purity of any seeds, if the impossibility of an
occasional cross has not been wholly excluded, either by the
circumstances themselves, or by experimental precautions taken during
the flowering period.
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