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Darwin, Charles, 1809-1882

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

Therefore as far as these few observations
serve, the advantage gained by a cross is very small.
Phaseolus vulgaris.
With respect to this species, I merely ascertained that the flowers were
highly fertile when insects were excluded, as indeed must be the case,
for the plants are often forced during the winter when no insects are
present. Some plants of two varieties (namely Canterbury and Fulmer's
Forcing Bean) were covered with a net, and they seemed to produce as
many pods, containing as many beans, as some uncovered plants growing
alongside; but neither the pods nor the beans were actually counted.
This difference in self-fertility between Phaseolus vulgaris and
multifloris is remarkable, as these two species are so closely related
that Linnaeus thought that they formed one. When the varieties of
Phaseolus vulgaris grow near one another in the open ground, they
sometimes cross largely, notwithstanding their capacity for
self-fertilisation. Mr. Coe has given me a remarkable instance of this
fact with respect to the negro and a white-seeded and a brown-seeded
variety, which were all grown together. The diversity of character in
the seedlings of the second generation raised by me from his plants was
wonderful. I could add other analogous cases, and the fact is well-known
to gardeners. (5/10. I have given Mr. Coe's case in the 'Gardeners'
Chronicle' 1858 page 829.


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