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Darwin, Charles, 1809-1882

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

The pistil is hook-shaped, with a plainly
enlarged stigma, which is curled down, towards the anthers; it therefore differs
much from that of the perfect flower. During the year 1867 no perfect flowers
were produced, but in the following year there were both perfect and
cleistogamic ones.
Ononis minutissima.
My plants produced both perfect and cleistogamic flowers; but I did not examine
the latter. Some of the former were crossed with pollen from a distinct plant,
and six capsules thus obtained yielded on an average 3.66 seeds, with a maximum
of 5 in one. Twelve perfect flowers were marked and allowed to fertilise
themselves spontaneously under a net, and they yielded eight capsules,
containing on an average 2.38 seeds, with a maximum of 3 in one. Fifty-three
capsules produced by the cleistogamic flowers contained on an average 4.1 seeds,
so that these were the most productive of all; and the seeds themselves looked
finer even than those from the crossed perfect flowers. According to Mr. Bentham
O. parviflora likewise bears cleistogamic flowers; and he informs me that these
flowers are produced by all three species early in the spring; whilst the
perfect ones appear afterwards, and therefore in a reversed order compared with
those of Viola and Oxalis. Some of the species, for instance Ononis columnae,
bear a fresh crop of cleistogamic flowers in the autumn.


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