In these two cases flowers were fertilised with pollen from a distinct
variety, and this was shown to be prepotent by the character of the
offspring. Nearly similar results often follow when two or more
self-fertile varieties are allowed to grow near one another and are
visited by insects. The common cabbage produces a large number of
flowers on the same stalk, and when insects are excluded these set many
capsules, moderately rich in seeds. I planted a white Kohl-rabi, a
purple Kohl-rabi, a Portsmouth broccoli, a Brussels sprout, and a
Sugar-loaf cabbage near together and left them uncovered. Seeds
collected from each kind were sown in separate beds; and the majority of
the seedlings in all five beds were mongrelised in the most complicated
manner, some taking more after one variety, and some after another. The
effects of the Kohl-rabi were particularly plain in the enlarged stems
of many of the seedlings. Altogether 233 plants were raised, of which
155 were mongrelised in the plainest manner, and of the remaining 78 not
half were absolutely pure. I repeated the experiment by planting near
together two varieties of cabbage with purple-green and white-green
lacinated leaves; and of the 325 seedlings raised from the purple-green
variety, 165 had white-green and 160 purple-green leaves. Of the 466
seedlings raised from the white-green variety, 220 had purple-green and
246 white-green leaves.
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