It is worth while to dwell a moment on the capacity of the individuals
with red flowers to reproduce the striped type among their offspring.
For it is manifest that this latter quality must have lain dormant in
them during their whole life. Darwin has already pointed out that when a
character of a grandparent, which is wanting in the progeny, reappears
in the second generation, this quality must always be assumed to have
been present though latent in the intermediate generation. To the many
instances given by him of such alternative inheritance, the
monochromatic reversionists of the striped varieties are to be added as
a new type. It is moreover, a very suggestive type, since the latency is
manifestly of quite another character than for instance in the case of
Mendelian hybrids, and probably more allied to those instances, [325]
where secondary sexual marks, which are as a rule only evolved by one
sex, are transferred to the offspring through the other.
Stripes are by no means limited to flowers. They may affect the whole
foliage, or the fruits and the seeds, and even the roots. But all such
cases occur much more rarely than the striped flowers. An interesting
instance of striped roots is afforded by radishes. White and red
varieties of different shapes are cultivated. Besides them sometimes a
curious motley sort may be seen in the markets, which is white with red
spots, which are few and narrow in some samples, and more numerous and
broader in others. But what is very peculiar and striking is the
circumstance, that these stripes do not extend in a longitudinal, but in
a transverse direction. Obviously this must be the effect of the very
notable growth in thickness. Assuming that the colored regions were
small in the beginning, they must have been drawn out during the process
of thickening of the root, and changed into transverse lines. Rarely a
streak may have had its greatest extension in a transverse direction
from the beginning, in which case it would only be broadened and not
definitely changed in its direction.
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