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Darwin, Charles, 1809-1882

"Effects of Cross and Self Fertilisation in the Vegetable Kingdom"


Cyclamen persicum--crossed and self-fertilised plants, left uncovered in
the greenhouse, produced capsules in number: 12.
Anagallis collina--crossed and self-fertilised plants, left uncovered in
the greenhouse, produced capsules in number: 8.
Primula veris--left uncovered in open ground and cross-fertilised by
insects: offspring from plants of the 3rd illegitimate generation
crossed by a fresh stock, compared with plants of the 4th illegitimate
and self-fertilised generation, produced capsules in number: 5.
Same plants in the following year: 3.5.
Primula veris--(equal-styled variety): left uncovered in open ground and
cross-fertilised by insects: offspring from plants self-fertilised for
two generations and then crossed by another variety, compared with
plants of the 3rd self-fertilised generation, produced capsules in
number: 15.
Primula veris--(equal-styled variety) same plants; average number of
seeds per capsule: 71.
Primula veris--(equal-styled variety) productiveness of the same plants,
as judged by the number of capsules produced and the average number of
seeds per capsule: 11.
This table includes thirty-three cases relating to twenty-three species,
and shows the degree of innate fertility of plants of crossed parentage
in comparison with those of self-fertilised parentage; both lots being
fertilised in the same manner. With several of the species, as with
Eschscholtzia, Reseda, Viola, Dianthus, Petunia, and Primula, both lots
were certainly cross-fertilised by insects, and so it probably was with
several of the others; but in some of the species, as with Nemophila,
and in some of the trials with Ipomoea and Dianthus, the plants were
covered up, and both lots were spontaneously self-fertilised.


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