Their structure is described by H. Muller 'Befruchtung'
etc., page 122.); and thirdly, from the greater fertility of the flowers
when crossed with pollen from a distinct plant than when spontaneously
self-fertilised. In the year 1863 I enclosed a large branch in a net,
and crossed five flowers with pollen from a distinct plant; these
yielded capsules containing on an average 35.2 very fine seeds, with a
maximum of forty-two in one capsule. Thirty-two other flowers on the
same branch produced twenty-eight spontaneously self-fertilised
capsules, containing on an average 17.2 seeds, with a maximum in one of
thirty-six seeds. But six of these capsules were very poor, yielding
only from one to five seeds; if these are excluded, the remaining
twenty-two capsules give an average of 20.9 seeds, though many of these
seeds were small. The fairest ratio, therefore, for the number of seeds
produced by a cross and by spontaneous self-fertilisation is as 100 to
59. These seeds were not sown, as I had too many other experiments in
progress.
In the summer of 1867, which was a very unfavourable one, I again
crossed several flowers under a net with pollen from a distinct plant,
and fertilised other flowers on the same plant with their own pollen.
The former yielded a much larger proportion of capsules than the latter;
and many of the seeds in the self-fertilised capsules, though numerous,
were so poor that an equal number of seeds from the crossed and
self-fertilised capsules were in weight as 100 to 45.
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