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Darwin, Charles, 1809-1882

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

The single long-styled plant which
was left uncovered, and grew close by the uncovered short-styled plant, produced
five good pods; but it was a poor and small plant.
The flowers borne on the thirteen short-styled plants under the net, which were
not fertilised, produced twelve capsules, containing on an average 5.6 seeds. As
some of these capsules were very fine, and as five were borne on one twig, I
suspect that some minute insect had accidentally got under the net and had
brought pollen from the other form to the flowers which produced this little
group of capsules. The one uncovered short-styled plant which grew close to the
uncovered long-styled plant yielded twelve capsules.
From these facts we have some reason to believe, as in the case of L.
grandiflorum, that the short-styled plants are in a slight degree more fertile
with their own pollen than are the long-styled plants. Anyhow we have the
clearest evidence, that the stigmas of each form require for full fertility that
pollen from the stamens of corresponding height belonging to the opposite form
should be brought to them.
Hildebrand, in the paper lately referred to, confirms my results. He placed a
short-styled plant in his house, and fertilised about 20 flowers with their own
pollen, and about 30 with pollen from another plant belonging to the same form,
and these 50 flowers did not set a single capsule.


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