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Darwin, Charles, 1809-1882

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


On account of the probability of some of the flowers on the plants of both
forms, which were covered under the same net, having been legitimately
fertilised in an accidental manner, the relative fertility of the two legitimate
and two illegitimate unions cannot be compared with certainty; but judging from
the number of good seeds per capsule, the difference was at least in the ratio
of 100 to 7, and probably much greater.
Hildebrand tested my results, but only on a single short-styled plant, by
fertilising many flowers with their own-form pollen; and these did not produce
any seed. This confirms my suspicion that some of the few capsules produced by
the foregoing seventeen short-styled plants were the product of accidental
legitimate fertilisation. Other flowers on the same plant were fertilised by
Hildebrand with pollen from the long-styled form, and all produced fruit. (3/2.
'Botanische Zeitung' January 1, 1864 page 2.)
The absolute sterility (judging from the experiments of 1861) of the long-styled
plants with their own-form pollen led me to examine into its apparent cause; and
the results are so curious that they are worth giving in detail. The experiments
were tried on plants grown in pots and brought successively into the house.
FIRST.
Pollen from a short-styled plant was placed on the five stigmas of a long-styled
flower, and these, after thirty hours, were found deeply penetrated by a
multitude of pollen-tubes, far too numerous to be counted; the stigmas had also
become discoloured and twisted.


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