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Darwin, Charles, 1809-1882

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


Twelve short-styled flowers were in this instance castrated, and afterwards
fertilised legitimately with pollen from the long-styled form; and they produced
seven fine capsules. These included on an average 7.6 seeds, but of apparently
good seed only 4.3 per capsule. At three separate times nearly a hundred flowers
were fertilised illegitimately with their own-form pollen, taken from separate
plants; and numerous other flowers were produced, many of which must have
received their own pollen. From all these flowers on the seventeen short-styled
plants only fifteen capsules were produced, of which only eleven contained any
good seed, on an average 4.2 per capsule. As remarked in the case of the long-
styled plants, some even of these capsules were perhaps the product of a little
pollen accidentally fallen from the adjoining flowers of the other form on to
the stigmas, or transported by Thrips. Nevertheless the short-styled plants seem
to be slightly more fertile with their own pollen than the long-styled, in the
proportion of fifteen capsules to three; nor can this difference be accounted
for by the short-styled stigmas being more liable to receive their own pollen
than the long-styled, for the reverse is the case. The greater self-fertility of
the short-styled flowers was likewise shown in 1861 by the plants in my flower-
garden, which were left to themselves, and were but sparingly visited by
insects.


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