But Mendel studied the
relation of other characters of the pea, and found among other results
that smooth seeds are dominant to wrinkled seeds, colored seeds dominant
to white, yellow color dominant to green, etc. But when a combination of
_two_ factors in each parent are put into contrast by cross breeding,
two wholly original forms (as they seemed) were sometimes produced, and
it looked as if these new kinds were really analogous to new species.
For example, he crossed tall yellow peas with dwarf green peas, with
the result that the first hybrid generation turned out to be all tall
yellows. However, in the second hybrid generation they split up
according to the law as already stated, modified by the additional
complication brought into the problem by the additional pair of factors.
For out of every sixteen plants there were nine tall yellows, three
_dwarf yellows_, three _tall greens_, and one dwarf green. It is evident
that these tall greens and dwarf yellows are really new forms; and
further experiments proved that they can be separated out or segregated
and grown as pure forms which thereafter breed true. Thus we have a very
important result for the breeder, for it enables him to work to a
definite aim and combine certain desirable characters into a single
form.
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