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Darwin, Charles, 1809-1882

"The Different Forms of Flowers on Plants of the Same Species"

In my concluding remarks I shall recur to
this fact, which at first appears inexplicable.
[PLANT 21.
This short-styled plant, freely and legitimately fertilised during 1865 by
illegitimate plants, descended from self-fertilised long-, mid- and short-styled
parents, yielded an average from ten capsules of 43 seeds, with a maximum of 63
and a minimum of 26: hence this plant, which was the one with all its longer and
many of its shorter stamens contabescent, produced only 52 per cent of the
proper number of seeds.
PLANT 22.
This short-styled plant produced perfectly sound pollen, as viewed under the
microscope. During 1866 it was freely and legitimately fertilised by other
illegitimate plants belonging to the present and the following class, both of
which include many highly fertile plants. Under these circumstances it yielded
from eight capsules an average of 100.5 seeds, with a maximum of 123 and a
minimum of 86; so that it produced 121 per cent of seeds in comparison with the
normal standard. During 1864 it was allowed to be freely and legitimately
fertilised by legitimate and illegitimate plants, and yielded an average, from
eight capsules, of 104.2 seeds, with a maximum of 125 and a minimum of 90;
consequently it exceeded the normal standard, producing 125 per cent of seeds.
In this case, as in some previous cases, pollen from legitimate plants added in
a small degree to the fertility of the plant; and the fertility would, perhaps,
have been still greater had not the summer of 1864 been very hot and certainly
unfavourable to some of the plants of Lythrum.


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